1. Support students to develop a critical sense of curiosity about scientific endeavours.
2. Prepare students to critically address science-related socio-economic and environmental issues.
3. Provide students with the foundation in science to prepare them for higher levels of study and science-related careers.
4. Enable students to use science and technology to think about how to solve everyday problems so that they may improve the quality of their own lives and the lives of others.
Matter is anything that has mass and volume (occupies space). The amount of matter in an object is called Mass. Mass can be measured in milligrams (mg), grams (g) or kilograms (kg). An object's mass remains the same. Weight is a measure of the pull of gravity on an object. Therefore the weight of an object changes depending on the gravity. You would weigh less on the moon than you would weigh on Earth because the moon has less gravitational pull.
The Particle Model of Matter is a scientific description of the tiny particles that make up all things. The key elements in this model include:
Matter can be found in three common states namely: solids, liquids and gases.
Solids have a shape and take up a fixed amount of space. In solids, the particles of matter are packed tightly and mostly in a regular pattern and cannot be easily compressed. The particles form a pile when they are poured; (they do not continue to flow apart from each other). The pencil, pen, book, desk, blocks, wood, ice ... are all solids.
Liquids do not have a fixed shape, they take the shape of the container. In liquids, the particles that make up matter are farther apart, there is little free space between particles. They are not easily compressible. Liquids can be poured and will always flow to the lowest possible level of the container and form a flat surface at rest. Water, juice, milk, and oil are examples of liquids.
If you pour juice into a glass, it goes to the bottom of the glass makes the glass half full. Gases do not have a fixed shape. If poured, gases spreads out throughout the container and do not flow to the lowest possible level. In gases, the particles spread out so as to fill the space in the container. If the space is small, the particles will be tight together, if the space is big, the particles will be spread out farther apart. Air is mostly made out of gases.
The most common form of matter in our universe exists in a fluid state called plasma, which is a gaslike mixture of positively and negatively charged particles. It is often considered to be the fourth state of matter.
Plasma is the fourth state of matter, defined as an ionized, high-energy gas consisting of free electrons and positive ions. Unlike gas, plasma conducts electricity, responds to magnetic fields, and is formed by extreme heating. It makes up over 99% of the visible universe, found in stars, lightning, and neon lights.
Changes of State: A change of state occurs when the particles of a substance gain or lose energy. Because this change is due to kinetic energy, the change of state is a physical process, which is reversible, and no matter how much kinetic energy is put into or taken away from the material, the material will always stay the same and its mass will also remain the same.
All substances are either pure or mixtures. Pure substances can either be elements or compounds. Pure substances have unique set of properties, or characteristics that remain consistent. Mixtures can either be homogenous or heterogenous based on the interactions between the elements in the mixture.
Element
An element is a pure substance with its own set of physical and chemical properties that cannot be broken down into simpler chemical substances. It has only one type of atom present.
Compound
A compund is a pure substance that can be broken down by a chemical change into two or more elements. Compounds have more than one type of elements that are chemically combined.
Mixtures are two or more substances that are NOT chemically combined. They do not have constant characteristics such as boiling or melting points. The components retain their characteristic properties. They may be separated into pure substances by physical methods. Mixtures of different compositions may have widely different properties.
Homogenous Mixtures
These are mixtures which look as though they have only one set of properties. The blended mixture has equal amounts of both substances (all parts of the mixture are the same). If the homogenous mixture does not have any settling of any of the substances it is made of, then it is called a solution. Solutions occur because each particle interacts with other particles and the resultant particles are evenly distributed throughout the entire mixture. In solutions, the substance in the smallest amount and the one that dissolves or disperses is called the SOLUTE. The substance in the larger amount is called the SOLVENT. water is commonly called the universal solvent. The gases, liquids, or solids dissolved in water are the solutes.
Heterogenous Mixtures
In a heterogenous mixture, the properties of the pure substances, can still be observed. If you notice there are two or more materials that are visible within a mixture, then it is a heterogeneous mixture.
In-Between Mixtures
There are several mixtures that cannot be classified simply as homogenous or heterogenous. If you observe a mixture in which the particles settle slowly after mixing, this type of mixture is called a suspension (Such as orange juice.)
A heterogeneous mixture, in which the particles do not settle at all, is called a colloid (eg. milk, fog, smog etc.) Colloids are solutions. They can be described as a substance trapped inside another substance. They can be identified by their characteristic scattering of light. For example: air trapped inside the fat molecules in whipped cream. The particles in colloids are smaller than a suspension but larger than molecules.
Mixtures that are obviously/visibly two or more substances are called mechanical mixtures. The separate parts of the mechanical mixture are called phases.
An emulsion is a mixture of two or more liquids that are normally immiscible owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloids. An emulsifier is a substance that stabilizes an emulsion by reducing the oil-water interface tension. Emulsifiers are a part of a broader group of compounds known as surfactants. Some examples of emulsions include homogenized milk, mayonnaise, butter etc.
Mixing and Dissolving
Some substances pull apart into individual molecules when placed in other substances. The dissolving substance is the SOLUTE. The substance doing the dissolving is the SOLVENT. The particles spread apart equally throughout the solvent to create a SOLUTION. Increasing the temperature will increase the solubility, more can dissolve. Is expressed as a concentration. Mass of solute/mass of solvent at a certain temperature.
Water - The Universal Solvent
97% of the water on Earth is Ocean water, 2% is frozen and only about 0.5% is 'usable'. Water is called a 'universal solvent' because it can dissolve so many materials.
The Rate of Dissolving
The rate at which a solute dissolves in a solvent is called the rate of dissolving and is influenced by:
Agitation (such as shaking, stirring etc.)
Temperature
Pressure
There is a limit to the amount of solute that can dissolve in a solvent. A saturated solution is one in which no more solute will dissolve in a specific amount of solvent at a specific temperature. An unsaturated solution is one in which more solute can be dissolved in a specific solvent at the same specific temperature.
Solubility Curves for Solids. The amount of solid which dissolves in water at a particular temperature is different for different substances. The next graph shows the solubility curves for potassium nitrate and sodium chloride. The temperature range shown is approximately 0 to 70°C. There is very little change in the amount of sodium chloride which dissolves over this temperature range but a very big change in the amount of potassium nitrate which dissolves.
The solubility curve for gases is the opposite of the solubility curve for solids. The solubility of a gas decreases as the temperature increases. The graph below shows the solubility curve for oxygen gas. The temperature range shown is approximately 0 to 50°C.
Saturation can be explained using the particle theory. In this case, the attractive forces between the particles becomes balanced and no more particles of the solute can be attracted by the particles of the solvent.
A solution that contains more solute than would normally dissolve at a certain temperature is called a super-saturated solution.
Some solvents are used for special circumstances because they will dissolve some solutes that water and other solvents cannot. For example, rubbing alcohol is use to dissolve chlorophyll (grass stains) from clothes. Perchloroethethylene is the solvent used in 'dry' cleaning, even though it is a liquid.
Solid particles can be removed from a mixture by filtration. The success of this technique depends on the pore size of the filter medium. Particles smaller than the pores will cross and form part of the filtrate.
Solvents can be removed by distillation and crystallization. Distillation is a separation method that allows all the liquid fractions of a mixture to be separated from each other and collected independently.
Purification of salt water (Desalination) can be done through distillation where the water boils at 100 C, leaving the salt behind to crystallize, the water can now be condensed and drunk.
Desalination can also be achieved through evaporation. The concept is similar to distillation but can be applied under different conditions.
Fractional distillation
Is the process used to separate the mixture of hydrocarbons in petroluem products. When the petroleum is heated, it changes into a gas (vaporize), which is collected and cooled, enabling it to change back into a liquid. The different components of the mixture condense at different temperatures therefore they recondense in separate fractional parts. Fractional products can then be further processed into over 500,000 types of petrochemicals.
Particle theory refers to the idea that all matter is composed of tiny, indivisible particles. Depending on the substance itself, these particles can be atoms, molecules, or subatomic particles such as protons, neutrons, and electrons. The concept of particle theory helps explain the behavior and properties of matter at the microscopic level.
Particle theory is a fundamental concept in chemistry and physics, providing a framework for understanding the properties and behavior of matter at the microscopic level. It has been instrumental in advancing our understanding of various phenomena, including phase changes, chemical reactions, and the behavior of gases.
Let us review some of the concepts in the particle theory:
Particles are always in motion, and the kinetic energy of their movement increases with temperature. This motion is responsible for the macroscopic properties of matter, such as its state (solid, liquid, or gas) and its ability to conduct heat.
There is empty space between particles, even though matter may appear solid. This is why substances can be compressed or expanded.
There are attractive forces between particles, which vary depending on the type of particles and the state of matter. For example, solids have strong forces of attraction, liquids have weaker forces, and gases have very weak forces.
The arrangement and motion of particles determine the state of matter. In a solid, particles are closely packed and vibrate in fixed positions. In a liquid, particles are still closely packed but can move past each other. In a gas, particles are more spread out and move freely.
Viscosity
Viscosity is a property of fluids (liquids and gases) that quantifies their internal resistance to flow. It arises from the interaction between the molecules of the fluid as they move past each other. Understanding viscosity is important in designing processes, optimizing fluid flow in pipelines, developing products, and ensuring the proper functioning of various systems in different industries.
Factors Influencing Viscosity:
Temperature: Generally, viscosity decreases with an increase in temperature for liquids and increases for gases.
Composition: The type and size of molecules in a fluid influence its viscosity. Larger and more complex molecules often result in higher viscosity.
Viscosity in Liquids:
High Viscosity: Substances like honey and molasses have high viscosity, meaning they flow slowly.
Low Viscosity: Water and most common liquids have lower viscosity and flow more easily.
Measuring Viscosity
Flow rate is a measure of a liquid's viscosity. The flow rate of a fluid is measured in ml/s (milliliters per second). By measuring the flow rate, we are able to compare the viscosity of different fluids because the thicker the fluid, the slower it flows and the more viscous it is.
Changing Viscosity
As previously mentioned, temperature affects the viscosity of a fluid. Increasing the temperature of a fluid will lower its viscosity. Lowering the temperature of a fluid will increase its viscosity.
Practical Applications
The principles of aerodynamics, drag and turbulence are associated with the concept of viscosity. Examine why these principles are related to how thick a fluid is.
Motor Oil is used as a lubricant in engines at different temperatures in different regions and in different seasons of the year.
Cooking requires knowledge of the effects that temperature has on viscosity. Which explains why sauces get thicker as they cool.
Density is a physical property of matter that measures how much mass is contained in a given volume. It is often expressed as mass per unit volume and is a fundamental concept in physics and chemistry.
The units for density depend on the units used for mass and volume. Common units include kilograms per cubic meter (kg/m続) in the metric system and grams per cubic centimeter (g/cm3) or kilograms per liter (kg/L) in other systems.
As mass increases while volume remains constant, density increases. As volume increases while mass remains constant, density decreases.
Measurement of Density
As the formula above, you can calculate the density of an object if you know its mass and volume. The mass can be measured using a balance.
The method to estimate the objects volume depends on whether the object is regularly shaped or irregular. The volume of a regularly shaped is obtained by measuring its legnth, Witdh and Height where Volume = L*W*H.
One way to determine the volume of an irregular object is to measure its mass in air and then in water, subtract the second measurement from the first, and divide by the density of water.
Another way to determine the volume of an irregularly shaped object is to submerge the object in a full container of water. The volume of the object equals the volume of water that overflows, (ie. that it displaces)
To determine the volume of an object that floats, first attach a metal sinker to the object. Next, submerge the metal sinker and measure the over-flow. Then submerge the object and measure the total overflow. The volume of the object equals the difference between the measurements.
The density of water is often used as a reference point. Water has a density of 1 g/cm続 or 1000 kg/m続 at standard conditions.
Density can be affected by temperature and pressure changes. For gases, an increase in temperature often leads to a decrease in density, while an increase in pressure typically increases density.
Hydrometers:
A hydrometer is a device that uses buoyancy to measure density directly. Hydrometers are calibrated in g/ml, by making marks that indicate the levels at which the instrument floats in different fluids. The higher the hydrometer floats, the higher the density of the liquid.
Density is often used to identify substances. Each material has a characteristic density, allowing scientists to determine the composition of unknown substances. Buoyancy: The principle of buoyancy is related to density. Objects float or sink in a fluid depending on their density compared to the density of the fluid.
Archimedes' principle
Archimedes' principle is a fundamental concept in fluid mechanics, named after the ancient Greek mathematician and inventor Archimedes. The principle states that when a body is partially or wholly submerged in a fluid (liquid or gas), it experiences an upward buoyant force equal to the weight of the fluid it displaces. This buoyant force acts in the opposite direction to gravity.
Applications:
Archimedes' principle is fundamental to understanding the behavior of ships, submarines, and other floating vessels. It is also essential in the design of hot air balloons, which rely on the principle to generate lift.
Density and Displacement:
The principle is directly related to the density of the fluid and the volume of fluid displaced. Less dense objects will displace more fluid and experience greater buoyant force.
Archimedes' principle is a key concept in fluid mechanics and plays a crucial role in understanding the behavior of objects in fluids, leading to practical applications in various engineering and scientific fields.
Bouyancy
Buoyancy: The buoyant force acts in the upward direction and is responsible for the apparent loss of weight of an object when immersed in a fluid. The object will experience a net force equal to the difference between its weight and the buoyant force.
Floating and Sinking:
If the weight of the object is equal to the buoyant force, the object will remain suspended in the fluid but will not sink (neutral buoyancy). If the weight is greater, the object will sink. If the weight is less, the object will rise to the surface.
Pressure is the force experienced by an object divided by the area of the surface on which the force acts. The force is acting perpendicular to the surface.
Atmospheric pressure, describes the pressure exerted by the weight of the air above us. The air goes up a long way, so even though it has a low density it still exerts a lot of pressure. On every square meter at the Earth's surface, then, the atmosphere exerts about 1.0 x 105 N of force. This is very large, but it is not usually noticed because there is generally air both inside and outside of things, so the forces applied by the atmosphere on each side of an object balance. It is when there are differences in pressure on two sides that atmospheric pressure becomes important.
Compressibility
The compressibility of a material is the ability to decrease the volume when pressure is applied. Gases are highly compressible. As pressure increases, the volume of the gas decreases. Liquids are nearly incompressible. As the pressure on the liquid increases, the volume remains unchanged.
Measuring Pressure
Pressure is measured by dividing the amount of force, by the area where the force is applied.
Where F is the force, and A is the area. 1 Pa = 1 N/m2
Other units include atmospheres (atm), millimeters of mercury (mmHg), and pounds per square inch (psi).
Barometers
A barometer is a scientific instrument used to measure atmospheric pressure. Atmospheric pressure, often referred to simply as "air pressure," is the force exerted by the atmosphere on a unit area and is an important parameter in weather forecasting. The barometer is a key tool for understanding changes in atmospheric pressure, which can indicate impending weather changes.
There are different types of barometers, but one of the most common is the mercury barometer, which was invented by Evangelista Torricelli in 1643. Here's how a mercury barometer works:
Principle of Operation:
The barometer is a sealed glass tube, typically about a meter in length, filled with mercury. The tube is closed at one end and open at the other end. The open end of the tube is inverted and submerged in a container of mercury. Atmospheric pressure exerts force on the surface of the mercury in the container, causing the mercury in the tube to rise or fall.
Mercury Column and Atmospheric Pressure:
The height of the mercury column in the tube is directly related to atmospheric pressure. As atmospheric pressure increases, the mercury column is pushed higher in the tube, and as atmospheric pressure decreases, the mercury column falls.
The atmospheric pressure is typically expressed in units of millimeters of mercury (mmHg) or inches of mercury (inHg). Standard atmospheric pressure at sea level is approximately 760 mmHg or 29.92 inHg.
Aneroid Barometer
Because mercury barometers are expensive and cumbersome, the aneroid (fluidless) barometer offers an alternative. The aneroid barometer is a spring balance, with a sealed, partially evacuated canister with flexible walls. A spring is inserted into the canister to keep the chamber from collapsing. Measurement of air pressure by an aneroid barometer involves balancing the weight of the atmosphere against a known spring force exerted upon the walls of the chamber. Increasing the outside air pressure collapses the walls of the canister slightly, because the pressure on the outside wall of the canister wall is greater than the pressure on the inner wall. While not as accurate as the mercury barometer, the aneroid barometer is more widely used because it is compact, portable, rugged, relatively cheap and it can be adapted to become a recording instrument, or a barograph.
Digital barometers are also common, providing a numerical readout of atmospheric pressure.
Fluid systems are present in living things and several man-made devices. Living things rely on fluid systems to transport important biochemicals needed for the body, thermoregulation, nervus system responses etc.
Hydraulic Systems: Fluid pressure is used in hydraulic systems to transmit force over a distance. This is commonly employed in machinery, car brakes, and heavy equipment. Barometers and Manometers: Devices like barometers and manometers measure atmospheric pressure and pressure differences in fluids, respectively.
Because force equals pressure multiplied by area, forces can be increase (by enclosing a liquid between two movable pistons of different areas)
Mechanical advantage: Is used in such hydraulic actuators as automobile brakes and the control flaps of airplanes. Hydraulic presses, invented by British engineer Joseph Bramah in 1796, are used to shape, extrude, or stamp metals and to test materials under high pressures.
Effort Force Advantage: The force is equal to the pressure multiplied by the area, so where the surface area is small, the force exerted is small, where the surface larger, the force exerted is larger.
Valves & Pumps
Valves and pumps are essential components in fluid control systems, playing crucial roles in regulating the flow of liquids or gases in various industrial, commercial, and residential applications.
Valves:
Valves are devices designed to control the flow of fluids by opening, closing, or partially obstructing passages.
Types of Valves:
Gate Valve: Provides a straight-through flow path when fully open; commonly used in applications where a straight-line flow of fluid is needed.
Ball Valve: Uses a spherical closure element to control flow; provides quick on/off control without pressure drop.
Butterfly Valve: Uses a disc mounted on a rotating shaft to control flow; suitable for large-volume applications.
Check Valve: Allows flow in one direction only, preventing backflow.
Control Valve: Modulates the flow of fluid to control the process.
Valves are essential in many applications including:
Water and Gas Systems: Valves regulate the flow of water and gas in plumbing systems.
Oil and Gas Industry: Used in pipelines and refineries for flow control.
Manufacturing Processes: Control the flow of liquids or gases in industrial processes.
HVAC Systems: Regulate the flow of air and water in heating, ventilation, and air conditioning systems.
Pumps
Pumps are mechanical devices designed to move fluids (liquids or gases) from one place to another by creating a flow. Pumps are essential in:
Water Supply: Pumps are used to supply water for various purposes, from residential water wells to municipal water distribution systems.
Chemical Industry: Pumps handle the transfer of chemicals in manufacturing processes.
Oil and Gas Industry: Essential for transporting crude oil, natural gas, and refined products.
Wastewater Treatment: Pumps play a crucial role in moving wastewater through treatment processes.
Features of Pumps:
Head: The height to which a pump can raise a fluid.
Flow Rate: The volume of fluid moved per unit of time.
Efficiency: The ratio of the energy output to the energy input.
Types of Pumps
Centrifugal Pump: Uses a rotating impeller to impart energy to the fluid; widely used for water and low-viscosity liquids.
Positive Displacement Pump: Transfers a fixed amount of fluid with each cycle; includes gear pumps, piston pumps, and diaphragm pumps.
Reciprocating Pump: Uses a piston or plunger to create pressure; common in high-pressure applications.
Submarines are watercraft designed for deep underwater operations. They are capable of independent underwater travel and are used for various purposes, including military, scientific research, exploration, and undersea cable maintenance. Submarines operate beneath the water's surface, providing advantages such as stealth and the ability to operate in environments that surface vessels cannot.
Submarines have a cylindrical or streamlined hull designed to withstand the high pressures encountered at depth. The hull is typically made of steel or other strong materials.
How Submarines Work
When an object is underwater, it pushes aside (or "displaces") an amount of water equal to its volume. Subs can sink, rise, and float underwater. Subs do all this by adjusting the amount of water and air in their ballast tanks. When the tanks are full of air, the sub weighs less than the volume of water it displaces and it floats. When the ballast tanks are flooded with water, the sub weighs more than the water it displaces, and it sinks. To rise again, the sub reduces its weight by pushing compressed air into the ballast tanks. The air forces the sea water out, and the sub goes up toward the surface. To move beneath the surface and to hover, the amount of water in a submarine's ballast tanks is made equal to the weight of the water it is displacing.
A deep-diving submarine used to explore the ocean is called a submersible. Submersibles are usually smaller than submarines. They are often equipped with external cameras, manipulating arms, and special lights. Submersibles are built to do specific jobs, not for long-distance travel. We use them to help us recover "black box" flight recorders from wrecked airplanes, bury cables in the sea floor, investigate ancient shipwrecks, map the ocean floor, look for signs of undersea earthquakes, study marine life, repair damaged offshore oil wells, take rock samples of the ocean floor, and study ocean currents.
All living things require oxygen, water, food and a place to live. Oxygen is a gas found in the air and in water and it is very important for living things.
Living things can be differentiated from non-living things because living things carry out five life functions as follows:
Organisms have systems which perform the functions that keep them alive. Systems are made up of organs, and organs are made from tissue. Tissues are composed of cells.
All living things are made up of one or more cells. A cell is the basic unit of life and the smallest part of a living thing that is capable of life. Most cells are too small to be seen with the unaided eye. We need to use an instrument called a microscope to be able to visualize cells.
The term 'cell' was coined by a scientist called Robert Hooke, who was the first to develop a microscope and used it to study thin slices of cork.
Anton van Leeuwenhoek was a Dutch scientist who developed an improved version of the microscope that was almost ten times more powerful than the one developed by Hooke.
In 1831, another scientist named Robert Brown discovered the nucleus of a plant cell. After several sudies observing multiple tissues from plants, the German scientist Matthias Schleiden concluded that plants were made up of cells. Theodor Schwann conducted similar studies in animals and concluded that animal were also made up of cells. It was the work of these many scientists that resulted in the cell theory.
Technology improvements have lead to the development of compound light microscopes (2000X magnification) and electron microscopes (2,000,000X magnification). There are two types of electron microscopes:
TEM (transmission electron microscope) and
SEM (scanning electron microscope)
The microscope is a valuable tool for the investigation of the microorganisms.
The cell theory is a scientific theory first formulated in the mid-nineteenth century, that organisms are made up of cells, that they are the basic structural/organizational unit of all organisms, and that all cells come from pre-existing cells. Cells are the basic unit of structure in all organisms and also the basic unit of reproduction. The three tenets of the cell theory are:
All organisms are composed of one or more cells.
The cell is the basic unit of structure and organization in organisms.
Cells arise from pre-existing cells.
Organisms can either be unicellular (made up of only one cell) or Multicellular (made up of more than one cell, and may be made up of trillions of cells.) Cells can specialize to perform specific functions. For example, blood cells, muscles, nerves are all specialized to perform their function.
Parts of a Cell: The human body has more than 200 different kinds of cells. Plant and animal cells have several basic structures in the cell, called organelles.
Plant and animal cells differ in:
Animal cell
Plant cell
The Nucleus
The nucleus is the brain of the cell. It is a large dark round spot inside Plant & Animal cells. It houses the nuclear DNA and controls the daily activities of the cell. Because it holds the genetic material in the DNA, it can be termed as the library of the cell. Inside the nucleus is a jelly-like fluid medium called the nucleoplasm, that provides support to the contents in the nucleus.
Cytoplasm
Inside the cell, but outside the nucleus is the cytoplasm, which is a gel-like substance that dissolves nutrients to be used for various physiological functions. The cytoplasm also suspends the organelles preventing them from crushing into each other.
Mitochondria
The mitochondria is the powerhouse of the cell. It produces ATP (Adenosine Triphosphate); which is the most common form of energy in the cell. The process involved in energy metabolism is referred to as Cellular Respiration. It is shaped like a sausage on the outside, but contains a double membrane on the inside (outer and inner membrane).
The structure of a mitochondria. (Source: genome.gov)
Vacuole
The vacuole appears hollow when viewed under a microscope. The organelle is more prominent in plant cells and is located somewhat at the center of the cell. Vacuoles function as storage organelles storing water, nutrients and waste.
Chloroplasts
Chloroplasts are only found in plant cells. They contain chlorophyll which s responsible for capturing light energy for photosynthesis.
Cell Wall
A cell wall is found in plant cells only. It is the rigid thick outer wall surrounding the cell. It gives the cell its regular shape and provides support to the plant. It's made up of cellulose which is also a structural molecule.
Cell Membrane
Also called Plasa membrane. It's present in both plants and animal cells. In plants, the cell wall is located on the inside surface of the cell wall. The cell membrane is made up of a phospholipid bilayer with other large molecules scattered. It retains cell contents inside the cell and allows movement of substances inside and outside the cell.
Chemical structure of a phospholipid and the phospholipid bilayer. (Source: Wikipedia-CC BY-SA 3.0)
The plasma membrane is composed of phospholipids and proteins. The phospholipids are organized in two layers thus referred to as a phospholipid bilayer. As the name suggests, a phospholipid has a phosphate head that is hydrophilic (water loving - can interact with water) and a lipid tail that is hydrophobic (water hating - does not interact with water). Due to this property, the phosphate heads are oriented towards the side of the plasma membrane where water molecules are located.
Transport across the cell membrane is either Active (requires energy) or Passive (does not require energy to occur).
Passive transport include Diffusion and Osmosis.
Simple Diffusion
The random movement of molecules from an area of higher concentration to an area of lower concentration until the concentration is uniform throughout the space, that's why when you add a drop of red dye into a clear glass of water it will spread throughout the water until it establishes an equilibrium.
Diffusion across a membrane
Membranes can be classified as:
Impermeable: does not let anything pass through the membrane
Permeable: allows all materials to pass through the membrane
Semi-permeable: allows some particles to pass through the membrane while excluding other particles
Diffusion can occur across a semi-permeable membrane, from the side with higher solute concentration (lower water concentration) to the side with lower solute concentration (higher water concentration), until the concentration is equal.
Dynamic Equilibrium
Dynamic Equilibrium describes a scenario where the diffusing particles are still moving, (diffusing) but the movement no longer results in a net change in concentration at one location, more than another location. When there is a membrane, dynamic equilibrium is a state where the diffusing molecules move across the membrane at almost the same rate in either direction.
Concentration Gradient: The difference in concentration between two locations. Molecules of substances move from high concentration to low concentration, so the larger the concentration gradient the faster the diffusion rate.
Temperature: Higher temperature results in faster diffusion rate.
Particle size: The larger the particle the slower the movement.
Facilitated diffusion uses transport proteins to facilitate the diffusion of particles across the plasma membrane. There are 2 types of transport proteins and they are recognized based on their shape, size, and electrical charge: Carrier Proteins are those protein that change shape to allow certain molecules to cross the membrane. Channel Proteins are proteins that form tunnel-like pores in the cell membrane, allowing electrically charged ions in and out of the cell.
Osmosis is the movement of water through a selectively permeable (semi-permeable) membrane from an area of higher water concentration to an area of lesser water concentration.
A solute are molecules that are dissolved in a solvent to form a solution. A solvent is substance that dissolves the solute. In most biological reactions, the solvent will be predominantly water. A solution is the result of dissolving a solute in a solvent.
The environment inside a cell can be described as Intracellular while the environment outside the cell is termed as Extracellular. Usually these two environments differ in their chemical composition.
In plant cells, when cells lose water, they shrink and the plant appears wilted. However, in cases where water is entering the cells, the cell walls in plant cells allow them to resist the pressure so they do not burst. This pressure created by water moving into the cells is called Turgor pressure.
Plants rely on a process called photosynthesis to obtain their energy. They utilize energy from the sun to produce food in form of glucose. The main ingredients (reactants) needed for photosynthesis to occur are carbon dioxide and water. The process produces glucose and oxygen.
Photosynthesis takes place inside chloroplasts. These organelles in plant cells contain the green pigment called chlorophyll. Chlorophyll captures energy from the Sun and the energy powers photosynthesis. The glucose produced in the process is stored within the plant. Oxygen, a waste product of photosynthesis, is released into the atmosphere.
Plants and animals use glucose as an energy source to perform various biological processes through a process called cellular respiration. Cellular respiration is like burning fuel to produce energy. It takes place in the mitochondria, an organelle found in the cell.
Cellular respiration can either be aerobic (requiring oxygen) or anaerobic (not requiring oxygen). Aeorbic respiration is more common when the oxygen supply to the cells meets the demand. Anaerobic respoiration (also called fermentation) occurs when the cells are not receiving sufficient oxygen for the needs. For example, during strenous exercise, the cells are utilizing energy much faster than can be produced by aerobic respiration.
| Cell Type | Special Structures | Functions |
|---|---|---|
| Muscle | Elongated and tapered on either end | Contracts and relaxes, moving parts of the body |
| Skin | Flat and thin, brick-shaped or honeycomb | Fit closely together to form a continuous protective layer |
| Nerve | Long branched fibres running from the main part of the cell | To carry nerve signals from one part of the body to another |
| Blood | Red Blood Cells are thin, disc-like | Increases the surface area making it more efficient to transport oxygen in the bloodstream |
| Bone | Thick, mineral matrix | To provide support |
Advantages of Multi-cellular organisms
Biological Organization
The single cell of a unicellular organism carries out all the functions necessary to keep the organism alive. A group of similar cells that perform the same function make up a Tissue. Animals are mostly composed of 4 types of tissue:
An Organ is a group of two or more types of tissue that work together to carry out a specific function. The skin is the largest organ with several layers made up of different tissues. The heart is also an organ that is made up of muscle tissue, connective tissue and nerve tissue. The brain, lungs and eyes are more examples of organs.
Plants also have organs namely the roots, stem and leaves. These support photosynthesis, absorption of water absorption and transport.
A group of organs working together is called an organ system. The circulatory system in humans combines the heart, blood vessels and blood to deliver oxygen and nutrients to various parts of the body and eliminate waste material. The repiratory system obtains oxygen from the environment and carries it to the blood where it enters the circultory system. Carbon dioxide from the blood enters the respiratory system and is released as a waste product.
The human body has ten major systems which include the skeletal, muscular, nervous, endocrine, cardiovascular, lymphatic, respiratory, digestive, urinary, and the reproductive system. These systems will be discussed in more detial in subsequent years.
In this section, you will learn the basics of some of the animal systems.
Living things obtain energy from food. Photosynthetic organisms can make their own food using the energy from the sun. Most other organisms obtain their food by consuming it in a process called ingestion. After the organism obtains (ingests) food, the food goes through a process where it is gradually broken down into smaller and simpler structures that the body can utilize for energy. Digestion is the process where ingested food is broken down into molecules that are usable by the body. Excretion is the removal ot waste material from the body. This waste material usually has little value to the body and in some cases, it can be toxic.
Digestive System
Invertebrates have several ways to digest food and release wastes. Sponges are filter feeders, the pores filter food from the water. In other invertebrates such as cnidarians and flatworms, food enters the body and leaves from the same opening. Invertebrates with more advanced digestive systems such as earthworms use a tube-within-a-tube system. These have separate openings for ingested food and for excreted wastes.
Vertebrates are more complex and so is their digestive system. They have many structures in order to handle different diets from teeth specialised to chew the type of food/feed, to digestive systems that have bacteria to help digest plant material.
HUman digestion starts in the mouth. Nutrients are absorbed in the small intestines and then move into the blood. Solid wastes are processed and eliminated from the body. The kidneys, liver, lungs and skin also help eliminate other types of waste material.
The product of digestion of carbohydrates is glucose, which is a simple sugar. Glucose is used by most of the body cells to make energy through a process called cellular respiration.
Respiratory System
Alhtough there is a connection between cellular respiration and the respiratory system, students should not be confused. The respiratory system relates to how to body obtains oxygen from the environment and releases carbon dioxide and moisture, which are waste products. The oxygen is needed for cellular respiration, and the carbon dioxide and moisture are the waste products from cellular respiration.
Some soft bodied invertebrates such as flatworms rely on simple diffusion for their exchange of gases. Diffusion is the movement of molecules from an area of higher concentration to areas of lower concentration. For oxygen to diffuse effectively, the surface must be moist, which is why most worms and snails stay in moist places.
Other invertebrates such as crustaceans have gills specialised for the gas exchange. Gills are feathery structures with a rich supply of blood vessels and the gas exchange occurs in these blood vessels.
As indicated previously, vertebrates are more complex in structure, which also means they have more complex systems. Amphibians live in water when they are young and on land when they are adults. Young amphibians have gills where gas exchange occurs. Adults have lungs for gas excahnge. Gas exchange can also occur through their skin in both young and adults.
Birds, mammals and reptiles use lungs exclusively for respiration.
In humans, air enters through the nose and mouth and passes through the pharynx then into the larynx and then trachea. The trachea divides into bronchi, then bronchioles and finally ends with sac-like structures called alveoli. Alveoli are very thin-walled and have high blood supply to allow gas exchange.
Circulatory System
The circulatory system is the body's transport system, it moves important materials such as oxygen, glucose and waste materials throughout the body to areas where the materials can be utilized, or eliminated.
Circulatory sytem can either be open or closed. In open circulatory system, the blood is not fully enclosed within blood vessels. Instead of moving into smaller blood vessels, the blood is released directly into the tissues. A closed circulatory system is where the blood is contained inside blood vessels. Materials diffuse in and out of the blood through the walls of the vessels.
Thermoregulation
Many processes in the body occur at a certain temperature. Therefore there is need for animals to maintain an internal temperature that will allow them to function properly. Some animals do not have to ability to regulate their body temperature and they rely on the environmental conditions. For example, when its hot, reptiles will burrow under rocks to stay cool, when its cold, they will bask in sunlight to stay warm. These animals that cannot regulate their internal tempeature and rely on the environment are named cold-blooded animals. Amphibians, reptiles and most fish are cold-blooded.
The blood vessels of the circulatory system form a complex network linking the outside environment with the internal environment of the body. The blood supplies all the living cells in the body with the nutrients they need to carry out their functions. About 8% of an adult's body weight is blood.
Blood Components
The circulatory system must work closely with the respiratory system (which supplies the oxygen) and the digestive system (which supplies the nutrients)
High blood pressure may be associated with several factors including high salt content, high epinephrine levels as in stress/freight, cancer, obesity etc. High blood pressure can cause heart attack, stroke, kidney damage etc. Low blood pressure is usually caused by low blood volume resulting from either bleeding, dehydration or severe anemia.
High fibre diet is important because fibre is used by the colon to process waste materials (low-fibre can irritate the colon wall and lead to colon cancer). Long-term stress, smoking, excessive use of alcohol or aspirin can lead to a peptic ulcer.
Poisons in cigarette smoke and pollutants irritate the lining of the lungs, causing certain cells to produce more mucus. If this lining becomes inflamed, it can lead to bronchitis, which can lead to emphysema. Lung cancer is caused by the tar and smoke in cigarettes, which cause the lung cells to grow out of control and overcome healthy cells.
Light is made of vibrating electric and magnetic energy. This energy travels as a wave, it has both frequency and amplitude. Light waves vibrate in a direction perpendicular to the direction of motion, i.e., transverse waves. Light waves can travel with or withour a medium. In a vacuum, light travels faster, but travels slower in a medium such as water, glass or air. Scientists have not found anything else that travels faster than light, and it is thought that the speed of light may be the speed limit of our universe.
The wavelength is the distance between one peak and the next peak in a wave. When you multiply the wavelength and the frequency, you get the speed of the wave.
Light as a particle
Light behaves both as a wave and also as a particle. light is like a particle in several ways. It travels in straight lines called light rays. Light does not have a mass, like a particle, but has momentum like a particle. When light hits a surface, it acts like a tiny particle. When light hits a camera film, it produces little dots instead of forming an image all at once. Over time, these dots will add up and form the original image. Light particles are called Photons. A photon is a tiny bundle of energy by which light travels. The energy is a single photon is very small. Each photon also acts like a wave, with a frequency. The higher the frequency the higher the energy.
When light hits an object, photons bounce off at random angles. This is called scattering. We see objects because as light scatters off them, it enters our eyes. Sometimes when light hits an object, light photons are absorbed. Darker surfaces absorb more light than lighter surfaces. When light is absorbed by a surface it is converted into thermal energy and the surface feels hot.
Light may also pass through some objects. Objects that allow light to pass through are called transparent. Objects that blur light as it passes through are called translucent. Objects that allow little to no light through are called opaque.
Opaque objects create a distinct shadow. A shadow is just the absence of light.
An image is a picture of the light source that light makes bouncing off a shiny surface. An image in a mirror is clear because most of the light waves reflect the same way off the mirrors smooth surface.
Laws of reflection
An image is formed in a mirror because light reflects off all points on the object being observed in all directions. The rays that reach your eye appear to be coming from a point behind the mirror. Because your brain knows that light travels in a straight line, it interprets the pattern of light that reaches your eye as an image of an object you are looking at.
Mirrors can also be made with curved surfaces. If they curve in, they are called concave. If they curve out they are called convex. Curved mirrors can form many kinds of images.
Convex mirrors form images that appear much smaller and farther away than the the object - but they can reflect light from a large area, making them useful as security devices.
Concave mirrors form an image that appears to be closer than it actually is and can be useful because it can also reflect light from a large area - side mirrors on automobiles.
Reflectors help to make bicycles and cars visible at night. A reflector is made up of hundreds of tiny, flat reflecting surfaces arranged at 90o angles to one another. These small surfaces are packed side by side to make the reflector. When light strikes the reflector the light bounces off the tiny surfaces and bounces back toward the light source.
Refraction
Refraction occurs when light waves bend as they pass from one medium to another or differing densities. Light waves entering a denser medium bend to make steeper angle with the surface. Rays leaving a denser medium bend in the opposite direction. Lenses are used in eyeglasses to make objects appear in focus. Convex lenses work like concave mirrors and concave lenses work like convex mirrors. Lenses are also used in cameras, telescopes and microscopes to change the size of the image.
Our eyes see and interpret light waves of different wavelengths as different colors. Visible light waves with longer wavelengths appear red. Visible light waves with shorter wavelengths appear violet. All colors fit between these two extremes. White light, like the kind from the Sun, is actually just a collection of many different wavelengths mixed together.
We can use a prism to refract white light into its component wavelengths. The band of color in a rainbow, or from light passing through a prism, is called a spectrum.
The picture on a color television is made up of red, green, and blue dots of light. All colors can be created by mixing red, green, and blue light in the right amounts and proportions. Red, green and blue are called primary colors. If all three are mixed equally, they produce white light.
When equal parts of red, green, and blue light rays are mixed, they form white light.
Light is a form of electromagnetic radiation. Electromagnetic radiations are made up of electric and magnetic waves that can move through space. There are many forms of electromagnetism nesides visible light, they differ in wavelength and the energy they carry. All considered together make up the electromagnetic spectrum.
The sun can produce all forms of electromagnetic radiations from infrared radiation, visible light and ultraviolet light. solar flares contain all forms of electromagnetic radiation.
Lenses play a crucial role in vision, both in the human eye and in optical devices.
Parts of the Human Eye:
Cornea: The outermost part of the eye is the cornea, which acts as a transparent window and helps focus light onto the lens.
Lens: The lens is a transparent, flexible structure behind the iris (colored part of the eye) that changes shape to focus light onto the retina.
Retina: Light focused by the lens forms an image on the retina, a light-sensitive layer at the back of the eye.
Focusing: The lens changes its shape through a process called accommodation to focus on objects at different distances. This process allows for clear vision at various distances.
Refraction: Light entering the eye is refracted (bent) by the cornea and lens to converge and form a focused image on the retina.
A lens is a curved piece of transparent material (glass/plastic). When light rays pass through it, the light is refracted, causing the rays to bend. A double concave lens is thinner and flatter in the middle than the edges. Light passing through the thicker more curved areas of the lens will bend more than light passing through the thinner areas, causing the light to spread out or diverge.
A double convex lens is thicker in the middle than around the edges. This causes the light to come together at a focal point, or converge.
The lens in the human eye is a convex lens, which focuses the light rays entering your eye to a point on your retina (a light sensitive area at the back of the eye). The image you see is formed on the retina. Some people however have eyes that are too long or too short. If their eye is too long, the image forms in front of the retina - this is a condition called Myopia, or near-sightedness
If their eye is too short, the image forms behind the retina, making object that are close to them difficult to see. This condition is called far-sightedness.
Applications of Lenses
Corrective Lenses:
1. Eyeglasses:
Concave lenses are used to correct nearsightedness (myopia), where distant objects appear blurry.
Convex lenses are used to correct farsightedness (hyperopia), where close objects appear blurry.
2. Contact Lenses:
Similar to eyeglasses, contact lenses correct refractive errors. They sit directly on the eye's surface.
Optical Devices:
1. Microscopes:
Lenses are fundamental components in microscopes, where they magnify and focus light to observe small objects.
2. Telescopes:
Telescopes use lenses or mirrors to gather and focus light from distant celestial objects, enabling astronomers to observe stars, planets, and galaxies.
3. Cameras:
Camera lenses focus light onto the camera sensor or film, forming images.
Eye and the Camera
In a camera, if an object moves closer to the film, the lens must move away to keep the image in focus. In the human eye, the lens cannot move, so the ciliary muscles change the shape of the lens (by making the lens bulge in the middle if the image comes closer to you and stretch if the object is further away). This is done so that the eyeball isn't stretched. The process of changing the shape of the lens is called accomodation. The shortest distance at which an object is in focus is called the near point of the eye. The longest distance is called the far point of the eye. On average, an adult has a near point of about 25 cm, whereas babies have a near point of only 7 cm.
In order to adjust the amount of light that enters the eye and the camera, a special device opens and closes to let just the right amount of light in. In the camera, the diaphragm controls the aperture (opening) of the lens and the shutter limits the passage of light. In the eye, the device (or part of the eye) that controls the amount of light entering is called the iris (the colored part of the eye), which changes the size of the pupil - in much the same way as the diaphragm controls the aperture (opening) of the camera lens. The natural adjustment in the size of the pupils is called the iris reflex, which is extremely rapid. This iris reflex action automatically adjusts the pupil when you go from a darkened area to a well lit area, or, from a well lit area to a darkened one.
The Film at the back of the camera contains light sensitive chemicals which change when light hits it. These chemicals form the image on the film. In the eye, when the cells in the retina detect light, they produce small electrical impulses from the retina to the brain by way of the optic nerve.
The point where the retina is attached to the optic nerve does not have any light sensitive cells. This point is known as the blind spot.
The parts of a camera are housed in a rigid light-proof box, whereas layers of tissue hold the different parts of the eye together. The eyeball contains fluids, called humours, which prevent the eyeball from collapsing and refract the light that enters the eye.
Telescopes
The telescope is a device used to form magnified images of distant objects.
In a refracting telescope, light from a distant object is collected and focused by a convex lens called the objective lens. A second lens, called the eyepiece lens, works as a magnifying glass to enlarge the image.
A reflecting telescope uses a concave mirror to collect rays of light from a distant object. This mirror is called the primary, or objective mirror, which forms a real image magnified by the eyepiece lens.
Binoculars
Binoculars are two reflecting telescopes mounted side by side. In binoculars, the telescopes are shortened by placing prisms inside, which serve as plane mirrors. In this way, the light entering the binoculars can be reflected back and forth inside a short tube.
Microscopes
A mangifying glass is a simple microscope with a low magnification. There are more advanced microscopes with much higher magnification and imaging technologies described earlier in this chapter.
Light waves are a form of electromagnetic radiation that propagate through space. They exhibit both wave-like and particle-like characteristics, known as wave-particle duality. The properties of light waves include wavelength, frequency, amplitude, and speed. The electromagnetic spectrum encompasses the entire range of light waves, from radio waves with long wavelengths to gamma rays with short wavelengths. Light waves can be reflected, refracted, diffracted, and polarized, interacting with various materials and mediums. Understanding light waves is crucial in fields such as optics, astronomy, and communication, and it plays a fundamental role in vision and technology.
Sunsets can be explained using the wave model of light. As light waves from the sun travel through Earth's atmosphere, they strike particles of different sizes, including dust and other elements. The longer wavelengths of the reds and oranges tend to pass around these particles, whereas, the shorter wavelengths of blue and violet, strike the particles and reflect and scatter.
Laser light, or simply laser (Light Amplification by Stimulated Emission of Radiation), is a type of coherent and focused light that has unique properties, making it useful in a wide range of applications.
Applications of laser
Lasers are used in several applications as follows:
Infrared
Their wavelengths are in millimeters. They are produced by vibrating molecules and atoms (heat) and lasers. Infrared wavelengths have been used extensively for military and civilian applications including target acquisition, surveillance, night vision, homing, and tracking. Non-military uses include thermal efficiency analysis, environmental monitoring, industrial facility inspections, detection of grow-ops, remote temperature sensing, short-range wireless communication, spectroscopy, and weather forecasting.
Ultraviolet
electromagnetic waves with a wavelength less than 400nm long. Produced by electrons dropping from very high energy levels to low energy levels. They are used for sterilizing materials, tanning, and generally in research. Ionizing radiations can knock electrons out of atoms and break bonds.
X- Rays
X-rays are produced by a sudden deceleration of very high-speed electrons. They are used in medical and industrial imaging. They are also ionizing radiations, this explains why X-rays can result in cancer, when they break bonds in DNA causing mutations or DNA damage.
Gamma Rays
Gamma rays are produced the decomposition of nuclei either spontaneously or by decelerating atomic nuclei. They are produced in nuclear reactions. They can penetrate matter very deep and can destroy carcinogenic or mutant cells hence they can be used in cancer treatment. They are ionizing radiations and can cause radiation sickness.
Radiation and Life
Radiation is energy travelling through space. Sunshine is one of the most familiar forms of radiation. There would be no life on earth without lots of sunlight, but we have increasingly recognised that too much of it on our persons is not a good thing. In fact it may be dangerous. so we control our exposure to it. Sunshine consists of radiation in a range of wavelengths from long-wave infra-red to shorter wavelength ultraviolet. Beyond ultraviolet are higher energy kinds of radiation which arc used in medicine and which we all get in low doses from space, from the air, and from the earth. Collectively we can refer to these kinds of radiation as lonising radiation. It can cause damage to matter, particularly living tissue. At high levels it is therefore dangerous, so it is necessary to control our exposure.
Radiation in the Environment
Natural radiation reaches earth from outer space and continuously radiates from the rocks, soil, and water on the earth. Background radiation is that which is naturally and inevitably present in our environment. Levels of this can vary greatly. A lot of our natural exposure is due to radon, a gas which seeps from the earth's crust and is present in the air we breathe.
What is a system? A system is a structure that has parts that are connected and influence each other in some way. It can be physical, such as a car, or organizational, such as the health care system. The input and output of a system are like the start and the finish. In order for the system to work it needs to have components that take the input and produce the output. When designing a system, considerations must be taken to maximize the effectiveness, the efficiency and the safety of the system
Levers
A lever is a simple machine consisting of a rigid barand a pivot point. The pivot is called a Fulcrum. The part of the bar on which a person applies an effort force is called the effort arm. The portion of the bar on which the lever produces an output force is called the resistance arm.
The positions of the fulcrum, effort force, and output force vary among levers. Based on these differences, there are three classes of levers.
First-Class Levers
In a first-class lever, the fulcrum is between the effort force and the output force. Therefore, a first class lever changes the direction of the effort force. The output force is greater than the effort force when the fulcrum is closer to the output force than to the effort force—that is, when the effort arm is longer than the resistance arm. The mechanical advantage can be calculated by dividing the distance the effort arm moves by the distance the resistance arm moves OR by dividing the length of the effort-arm by length of the resistance. A see-saw is an example of a first-class lever.
Second-Class Levers
In a second-class lever, the output force is between the effort force and the fulcrum. Second-class levers do not change the direction of the effort force. However, they produce a mechanical advantage because the effort arm is longer than the resistance arm. A wheelbarrow is an example of a second-class lever.
Third-class lever
In a third-class lever, the effort force is between the output force and the fulcrum. Like second-class levers, third-class levers do not change the direction of the effort force. But, unlike second-class levers, third-class levers always produce an output force that is less than the effort force. A fishing roda and the hand muscles are examples of third-class levers. A third-class lever multiplies the distance of the effort. A person would only need to move her hands a short distance to move the tip of the rod through a greater distance.
Inclined Planes
An inclined plane is a straight slanted surface that can multiply an effort force. It makes it easier to move a heavier load upward.
The mechanical advantage is equal to the output force divided by the effort force. Suppose two students use ramps to slide boxes weighing 300 newtons onto a stage. One student uses a steeper, shorter ramp and applies an effort force of 225 newtons. The other uses a shallower, longer ramp and applies an effort force of 135 newtons. The effort force of the steeper ramp is 225 newtons. Its mechanical advantage is 300 divided by 225, which equals 1.33. The effort force of the longer ramp is 135 newtons. Its mechanical advantage is 300 divided by 135, which equals 2.22. The longer ramp has the greater mechanical advantage. The mechanical advantage can also be calculated by dividing the length of the incline by the height.
Screw
A screw is another simple machine. The spiral ridges called threads move into an object as the head of the screw turns. The space between the threads is called the pitch. A screw’s mechanical advantage is calculated in a similar way to a ramp’s. If the distance around the head of a screw were 1.5 centimeters and its threads were 0.1 centimeters apart, its mechanical advantage would be 1.5 divided by 0.1, which equals 15.
Wedges
A wedge is an inclined plane that changes the direction of an applied effort force. A knife is a wedge. When you push down on a knife to cut food, the knife presses sideways against the food, pushing it apart. A wedge may be a single inclined plane or two inclined planes joined back-to-back. Wedges that are thin have greater mechanical advantages than those that are thick.
Wheel and Axle
The wheel and axle is a type of a first-class lever simple machine. There is a wheel that applies the effort force and a smaller axle that produces the output force. The mechanical advantage of a wheel and axle is calculated by dividing the length of the effort arm by the length of the resistance arm. The effort arm is the radius of the wheel. The resistance arm is the radius of the axle. Since the effort arm can be quite large compared to the resistance arm, this machine can have a large mechanical advantage.
Examples of wheel and axle machines
Gears
Like the wheel and axle, use rotation, but they transfer the rotation to a different axis, the gears are not attached, they use teeth that mesh together. The teeth on gears are very specifically designed. Their shape is one that allows them to be in contact with each other for as long as possible, but yet they do not cause an obstacle for rotation. Gears can be used to increase force (increase torque, increase mechanical advantage) or increase speed. They can also be used to change the direction or type of the force.
The mechanical advantage of gears is more complicated to understand than other examples, as it involves looking at torque, which we will not cover in grade 8. Instead, we will look at velocity ratio. First, we need to define the gears involved. The gear that you turn is called the "driver." The gear that turns as a result of the driver turning is called the "follower." Velocity ratio tells you how much faster the follower will turn than the driver. It is calculated as follows:
Alternatively, because of the carefully calculated way in which the teeth of gears are designed, you can also calculate velocity ratio by counting how many teeth are on the gears:
Pulley
Pulley is a grooved wheel that turns by the action of a rope in the groove. When the rope moves, the wheel turns. A pulley is also a type of lever, one in which the rope forms the arms and the wheel serves as the fulcrum.
A pulley may be either fixed or movable. A fixed pulley makes work easier by changing the direction of the effort force. It does not change the strength of the effort force itself.
The wheel of a movable pulley is attached to the object being lifted and moves with it. A single movable pulley multiplies the effort force by 2, so it has a mechanical advantage of 2. However, a single movable pulley does not change the direction of the effort.
A pulley system is made up of several pulleys acting together. Some pulley systems contain both fixed and movable pulleys. The addition of a fixed pulley enables the system to change the direction of the effort. The mechanical advantage of a pulley system can be expressed in terms of the distance it moves an object compared to the distance its rope must be pulled when the effort is applied. This can be done by by dividing the distance the effort rope moves by the distance the object moves. A simple way to measure the mechanical advantage of a pulley system is to count the number of rope strands pulled downward by the object being lifted. This number is the mechanical advantage of the system.
Work and Energy
In Science, work is defined as the force to move an object through a distance. Based on this definition, holding a heavy box in the same position results in no work being done because the box did not move.
Work is equal to the force of a push or pull multiplied by the distance the object is moved. The force must act in the same direction as the motion. If the force is expressed in newtons and the distance is expressed in meters, the units for the work done are newtonmeters (Nm), also called joules (J).
Suppose you use a rope to lift a bucket filled with rocks up to a tree house that is 5 meters high. The weight of the bucket is 30 newtons. You can calculate the work done by using the formula:
Energy is the ability to do work. Like work, energy is measured in joules. There are several forms of energy. For example, an object placed on an elevated position stores energy because of its position and the force of gravity. This energy is called Potential energy. An object that is in motion also carries energy called Kinetic energy. This is due to the obect's mass and speed.
Energy usually changes from one form to another. When an object is moving uphill, it slows down, which means it loses kinetic energy, but because its moving to a higher elevation, it gains potential energy. when the object begins to move downhill, it gains more kinetic energy and loses potential energy.
Thermal energy is the heat energy in an object.
Conservation of Energy
Energy cannot be created or destroyed, however, it can change from one form to another. All forms of energy have a source, a means of transfer, and a receiver. For example, in a flashlight the energy source is the potential energy in the battery. An electrical circuit enables the energy to be transferred to the bulb. The bulb is the receiver of this energy. It can then give off energy in the form of light and heat.
The following are examples of various forms of energy:
Changing Forms of Energy
Several devices convert one form of energy to another.
A hair dryer converts electrical energy into thermal energy
A speaker converts electrical energy into sound energy
A microphone converts sound energy into electrical energy
A bulb converts electrical energy into light energy (and some thermal energy).
Light energy from the sun is converted into chemical energy by the green leaves of trees through photosynthesis. This chemical energy can be transferred from plants to animals through ingestion. Some parts of the animals will convert this chemical energy into mechanical energy (muscles), thermal energy (for homeostasis), electrical energy (neurons) and sound energy (mouth).
Friction
Friction is the force that opposes the motion of an object. It occurs when two or more objects come into contact. For example, in order to move a book across a table, you must pull on it with a force that is greater than the force of friction that is reventing the book from moving.
There are many types of friction. For example, the force between the surfaces of two solid objects which keeps the objects from moving is called static friction. The force that opposes the sliding of an object over a surface is called sliding friction. Rolling friction is the force that opposes the motion of a wheel turning along a surface.
Friction is necessary to maintain position and prevent objects from falling. For example, friction is necessary when you want to stop your bicycle or to turn a corner. It prevents the wheels from slipping.
Friction and drag force are similar because both forces oppose motion. However, different types of friction do not depend directly on the size, shape, or speed of a particular moving object. In contrast, all three of these factors do affect drag force. For example, a crumpled piece of paper falls faster than another piece of the same paper that is not crumpled. This occurs because of the way that air affects differently shaped objects.
Net force is the sum of all the forces that are acting on an object. When the net forces are equal in strength and opposite in direction, they are balanced forces. The motion of an object remains unchanged. Forces of unequal strength or forces that are not opposite in direction are called unbalanced forces.
Balanced force
Unbalanced force
Efficiency
Efficiency is a ratio of the work obtained from a system to the work that is put into the system. If something was 100% efficient, you could put a set value of work into it, and achieve that exact amount of work from it. However, this is never truly the case.
Example:
A battery in a ride on toy car has 3000 J of energy left. It takes a force of 6 N, once started, on average, to keep the car moving? If a park is 400 meters away, should the parents let the kid ride his car there?
Work = Force X Distance
Distance = W / F
D = 6000 / 6 = 500 meters
This means, the car can ride a distance of 500 before the battery runs out. But the park is 400 meters away, so the car will be able to take the kids to the park but will not be able to get them back home because a round trip is in fact 800meters long.
If the car above ended up driving for only 480 meters, Efficiency can be calculated as:
Efficiency = Work Obtained / Work put in
= FxD / 3000 = 6 X 480 / 3000 = 0.96 = 96%.
So the car is only 96% efficient.
A force is a push or pull acting upon an object as a result of its interaction with another object. A force constantly applied to an object is called continuous force. A rocket engine provides thrust, which is a strong push in the direction opposite an object’s weight. Thrust causes the rocket to accelerate upward, away from the launch pad. This thrust will continue to be applied as long as the rocket engine burns fuel.
Types of Forces
We have already defined continuous force as that which gets exerted on an object continuously.
Momentary force is the type of force that acts on an object for a very short period of time. It can also be called impact force.
Friction is a force that opposes the motion of an object. Friction occurs when two or more objects come into contact.
Drag force occurs when an object moves through any liquid or any gas, such as air. This force opposes the motion.
Pascal's Law: The pressure in an enclosed fluid is uniform throughout.
For example, When a pipe is punctured, or if it is not sealed properly, the fluid will rush out of the pipe. This is because the fluid is under pressure, and so is pushing outwards on the pipe. With no pipe wall there to hold it back, it exits.
The leak would stop if the pressure inside the pipe was lowered to match the air pressure on the outside.
Pumps
A pump is a device that forces fluids into an area. By forcing the fluid into an area it creates pressure in the fluid. The water in your home is an example of this. Water is pumped through the city water lines, putting it under pressure. When your faucet is closed, the water is blocked from escaping. Once you open the faucet, the water is pushed out of the tap by the pump. As more and more faucets are opened, more water is released. This means the pump has to supply more water. If the pump can not keep up, you will lose "water pressure" i.e., the water will not come out as quickly, as there is not as much pressure in it.
Hydraulics
Fluids under pressure are not just used to supply things like water. We can use the force created by this pressure to make powerful tools.
Hydraulic System is a device that transmits a force through a liquid by using Pascal's law of constant pressure
Pneumatics
Sometimes gases are mor epractical to use.
Pneumatics is the study of pressure in gases.
A pneumatic system is a device that transmits a force by releasing a gas that is stored under pressure
Hydraulic systems use the force of a liquid in a confined space. Hydraulic systems apply two essential characteristic of fluids – their incompressibility and their ability to transmit pressure.
Pneumatic systems do not seal the gas (usually air) in the same way as hydraulic systems seal in the fluid it uses. The air usually passes through the pneumatic device under high pressure and then escapes outside the device. The high pressure air is used to do the work.
Examples of Pneumatic Systems
Staple guns and pneumatic nailers use pulses of air pressure to drive staples or nails into solid objects.
Sandblasters do exactly what the name implies. High pressure air blasts tiny sand particles out of a nozzle to remove dirt and paint from stone or rock.
Hovercrafts have a pump that draws air from outside and pumps it out through small holes in the bottom of the hovercraft.
Examples of Hydraulic Systems
A hydraulic system uses a liquid under pressure to move loads. It is able to increase the mechanical advantage of the levers in the machine. Modern construction projects use hydraulic equipment because the work can be done quicker and safer. There are many practical applications of hydraulic systems that perform tasks, making work much easier.
Earthmovers use hydraulics to move large amounts of dirt from place to place.
Hydraulics and Pneumatics in the Human Body
Life depends on the respiratory system, which is a pneumatic system in the body. The lungs that allow air to enter and leave the body as they contract and expand. Breathing depends on changes in air pressure resulting in intake or expulsion of air.
The body also depends on a complex hydraulic system – the circulatory system. The heart pumps the blood through blood vessels around the body, carrying food and nutrients to all cells.
A compound machine is a combination of two or more simple machines. For example, scissors include two levers and two wedges. The pivot point for the blades and handles is the fulcrum, and the blades are the wedges. A bicycle is also a compound machine. The pedals and wheel and axle machines. The gears are also wheel and axle machines. The brakes work as two levers.
The work put into a machine is always greater than its resulting work output because friction causes some of the work input to be lost usually as heat. The wasted energy reduces a machines efficiency. Efficiency is the ratio of the work done by a machine to the work that was put into it. To calculate efficiency, divide the output work by the effort work. Coating certain parts of a machine with substances such as oil can reduce friction thereby increase efficiency of a machine.
Prior to the industrial age, all products were hand made and every one was unique. In the early 1900's, however, a few individuals came up with the idea to standardize components so they may be interchangeable.
It is not just the automotive industry that has adapted automation and the assembly line as common practise. Now a days, most products are manufactured in this manner.
Famous machines that helped to change the world
Archimedes Screw. The ability to draw water uphill, against the flow of gravity revolutionised irrigation and the supply of water. Designed in 213 BCE by the polymath, Archimedes, the Archimedes screw is still used for irrigation today.
The printing press. In 1455, Johannes Gutenberg developed the first mechanised printing press. He converted an old wine press to enable a heavy screw to press a printing block against paper. His machine enabled a huge reduction in the cost of producing books and helped lead to a rise in literacy, knowledge and was a key part of the Enlightenment.
Calculator A very primitive form of the calculator was developed by Blaise Pascal. The first solid-state calculator was invented in the 1960s, with digital calculators using microprocessors being invented in the 1970s.
The Telescope. telescopeGalileo is credited with building the first telescope. This was later improved upon, and the first reflecting telescope was built in 1668 by Sir Isaac Newton. Newton used parabolic mirrors instead of lenses and which operated using reflection. His telescope designs would later be used in mapping the stars and gaining a much better understanding of the earth’s position in the Universe.
The Steam engine The first steam engine was built by Henry Newcomen in 1712, but this inefficient steam engine was limited to a stationary point, such as using in mines. James Watt played a key role in making the steam engine more efficient. The Steam Train. The first working steam engine is often credited to be Richard Trevithick in 1804. However, George Stephenson’s engines were more famous because of their greater impact. The Internal Combustion Engine The internal combustion engine enabled the development of the modern motor car and related transport.
Science and technology have given us many different amazing machines that have made our daily tasks easier. The automobile caught on very quickly, but the ideal machine soon demonstrated its greatest flaw. Pollution of the environment was a result of more and more fossil fuels being burned, in larger vehicles. Improving machines brought lots of positives, but there were also some negative side effects (like pollution).
The Industrial Revolution
The invention of the steam engine transformed society. Simple machinery replaced hand labor since 1700. Water-driven spinning machines were used in 1769 and could the work of 12 workers. James Watt’s efficient steam engine and Henry Cort’s use of coal for fuel (instead of wood) to make iron started the Industrial Revolution.
The question of whether technology changes society or society changes technology is still a challenge today. The automobile uses cheap fuel and therefore more vehicles are being used. With cities so large, people need a vehicle to travel from place to place. OR, is the convenience of having a vehicle just societies’ reason to have larger cities? Because of the impact of scientific knowledge on society preferences for styles and sizes of vehicles changed. Larger vehicles polluted more and cost more to operate, so society wanted more compact fuel efficient vehicles. Today alternative fuel sources (solar-powered, electricity, hybrids, propane and hydrogen fuel cells) are being tested and are utilized to a very small extent.
Designing for Comfort
The testing systems that designers use provide scientific information to researchers, allowing them to decide what type of modification is best for its designed purpose. Comfort is an important criterion that is evaluated. For example, the wheelchair has gone through many improvements over the years. These changes happened because of the research into ergonomic designs and pressure put on the designers by the consumer.
Living things need water to survive. Ecosystems also depend on it. The land is shaped by it. The climate and weather are influenced by it. About 74% of the Earth's surface is covered by water. However, 97% of this water is saltwater.
Water makes up a large component of living things with about 65% in humans, 84% in apples and 98% in water melons.
Agricultural practices such as irrigation use up about 70% of water. About 22% of water is used in various industrial applications and only 5% is used for domestic uses including drinking. Of course humans and other animals also obtain water through the food/feed they consume.
The Water Cycle
The water cycle is made up of three manin processes.
Evaporation
When water heats up, some of it changes into a gas called water vapor. This process is called evaporation.
Water evaporates from lakes, oceans, rivers, ponds and other water bodies.
Water can also evaporate from the surface of leaves in a process called transpiration.
Condensation
The water vapor travels in the air. As it rises into the air, it cools down and turns back into a liquid. The change from gas to liquid is called Condensation.. If many water droplets in the sky come together they form clouds. A cloud is a group of water droplets in the atmosphere.
Precipitation
The water in the clouds and the water vapor in the air will then fall down to the ground as rain or other kids of precipitation.
Precipitation refers to any liquid or frozen water that forms in the atmosphere and falls back to the earth. It comes in many forms, like rain, sleet, and snow.
If its too cold, the water droplets in clouds will freeze into ice. Freezing refers to the change from liquid to solid.
Some of the water that falls as precipitation collects on land and flows downhill. A watershed is an area from which water is drained. Precipitation that flows across the land’s surface and is not absorbed will flow into rivers, lakes, and streams as runoff. Most of the water will flow from rivers to the ocean. Some of the water will settle underground and become groundwater.
Plants and animals also play a role in the water cycle. Plants absorb water from the ground through their roots. Excess water in the plant is lost through transpiration. Animals drink water and then release the excess as waste and sweat.
Four countries (Brazil 18%, Canada 9%, China 9%, and United States 8%) hold nearly half of the Earth’s renewable supply of freshwater.
Ice Ages
The Earth has had 7 major Ice Ages over the last several million years. During this time glaciers covered approx. 28% of the Earth’s surface. In the last Ice Age, Canada was completely covered by a continental glacier.
A small change in the average temperature is enough to start a chain of events that can produce an Ice Age. For example, reduced thermal energy from the Sun, increased volcanic activity (adding clouds of ash into the atmosphere, thus reducing how much thermal energy from the Sun reaching Earth), Mountain building (more snow to accumulate and reflect sunlight resulting in reduced temperature, movement of Earth’s tectonic plates alters the shape of the oceans and affects ocean currents, causing less mixing of hot and cold water. a change in the tilt of the Earth’s axis may also alter the temperature etc.
Glaciers: A glacier is a thich sheet of ice that creeps over land. Glaciers form where snow collects quickly and melts slowly. Year after year, the snow builds higher. The weight on top of the mound puts pressure on the snow below. The bottom of the glacier slowly turns to ice. Melting makes the bottom of the glacier slippery. It begins to flow downhill. The bottom and sides freeze onto rocks. As the glacier continues to move, it tears rocks from the ground. It scratches, flattens, breaks, or carries away the things in its path. A glacier can make a valley wider and steeper. Glacial debris can be made of large boulders or small rocks. They can have bits of gravel, sand, soil, and clay. The glacier drops most of this debris at its downhill end, or terminus. Materials that a glacier picks up or pushes can forms mounds. These mounds are called moraines. Today, you can find glacial till and moraines across Canada and northern parts of the United States.
The Importance of Glaciers:
Icefields, glaciers, and snow – high up in the mountains – act as natural reservoirs, collecting snow in the cold months and releasing it as meltwater as it warms up. This meltwater helps run hydroelectric plants, irrigate crops, water cattle and supply drinking water. Glaciers slow the water cycle and provide important clues to understand historical climate patterns.
All glaciers begin as snowflakes. These snowflakes accumulate, becoming grains, ice crystals and the weight of the snow creates pressure that gradually changes the ice crystals into glacial ice.
Valley Glaciers
Glaciers form high in the mountains and move through valleys between mountain peaks. These are called valley glaciers.
Continental Glaciers
Those covering large areas of land are called continental glaciers or icecaps. Continental glaciers cover Antarctica and Greenland.
Glacial Features
The shapes that develop in flowing ice are unique. Where a glacier flows over a steep cliff and breaks up, an icefall results. A crevasse is a fissure, or crack, in the ice.
Pack ice is a sheet of ice that is rarely more than 5 meters thick that breaks easily. This usually happens in freezing sea water when large pieces break off as they move into warmer water.
Icebergs are large chunks of ice that break loose, or calve, from continental glaciers as the glaciers flow into the ocean. These chunks are visible as they move through the ocean, melting faster below the surface than above.
The collection of rocks, boulders, sand, clay and silt that is left behind as a glacier slows down and melts, is called till.
Long Term Temperature Changes
The greenhouse effect and global warming are two unrelated events that affect the average temperature on the Earth.
The greenhouse effect is the natural warming of the Earth caused by gases in the Earth’s atmosphere trapping heat.
Global warming is the increase of these greenhouse gases, which causes more heat to be trapped and the temperature around the world increases – causing ice caps to melt producing widespread flooding.
Water exists in all three forms on the Earth: solid, liquid and gas. It is found underground, on the surface and in the air.
A lake and a pond are holes in the ground filled with water. A lake is deeper than a pond and sunlight does not reach the bottom, whereas in a pond sunlight will penetrate right through to the bottom, depending on the clarity of the water. The clarity is determined by the amount of suspended solids in the water. In lowland areas, wetlands exist. They are saturated with water most of the time. Wetlands provide habitat for a vast diversity of living organisms.
An aquatic ecosystem is an ecosystem formed by surrounding a body of water, in contrast to land-based terrestrial ecosystems. Aquatic ecosystems contain communities of organisms-aquatic life-that are dependent on each other and on their environment. The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems
The organisms in water ecosystems are divided into three main categories. Plankton are creatures that drift freely in the water. They are not able to swim. Some plankton, such as diatoms, are producers, and others are consumers, such as some animal larvae.
The second group includes the larger, active swimmers in a body of water called nekton. Fish, turtles, and whales are all nekton. The third group, organisms that live on the bottom of a body of water, are called benthos. Many benthos are scavengers or decomposers because they feed on material that floats down from shallower water.
Unlike land ecosystems, water is never a limiting factor. However, the amount of light, dissolved salt, and dissolved oxygen are important. They can all affect the types of organisms that can live in bodies of water.
Running-Water Ecosystems: Faster-moving bodies of water tend to have more oxygen, because air mixes in as the water flows. Other nutrients are washed into the water from the land. Organisms that live in fast-moving streams or rivers have adaptations to prevent them from being swept away. Slower-moving waters have less oxygen and are less dependent on the land for nutrients. More producers, such as algae, are able to survive in slow-moving water.
Standing-Water Ecosystems: The typical freshwater lake or pond is divided into three zones. The shallow-water zone along the shore is where most of the organisms live. Cattails, sedges, arrowgrass, and other rooted plants grow here. The open-water zone includes the water away from the shore. This zone may be too deep for rooted plants to survive. Algae and plankton float near the surface. Nekton, such as trout, whitefish, and pike are found here. The third zone is below the openwater zone and includes the bottom. Very little light reaches the bottom, so producers cannot grow here. Benthos, including worms and mollusks, are found in this zone.
Freshwater Wetlands: Wetlands, such as marshes, swamps, and bogs, are regions that are wet for most of the year. Grasslike plants, moss, and some shrubs are found in wetlands. Beavers, muskrats, otters, birds, and fish live in wetlands.
A groundwater system is similar to a river system. Connecting pores in rocks and soil enable the water to seep through – making it permeable. This is called an aquifer. When the water reaches the bedrock, which is impermeable. The layer of porous rock, in which the connecting pores are full of water, forms the water table.
Wells and Springs: Wells are dug to reach the aquifer, below the water table. If too many wells are dug too close to each other, they may deplete the aquifer and the wells will dry up. If the water in an aquifer flows naturally to the surface, it is called a spring. Hot springs occur when this water is heated by rocks that come into contact with molten material below the Earth’s surface.
Watersheds and Land Use
Storm drains in a city act as a watershed to remove water from the streets after a heavy rainfall. The paved roadways change the run-off patterns in a city, because the water would normally seep into the ground. Logging can also affect watersheds. GIS (Geographic Information Systems) are used to store data and generate maps showing a river’s watershed, allowing them to predict what would happen if runoff patterns changed. The amount of water discharged by a watershed is influenced by soil conditions, vegetation, and human activity.
Aquifer Depletion: Underground aquifers supply water to many cities, farming communities and industries. If too much is used, the aquifer can become depleted, drying up creeks, springs and wells for many kilometres. Responsible use of water is essential in order to sustain this natural resource.
Contaminants in groundwater can spread the effects of dumps and spills far beyond the point source. Non-point sources are those where a pollutant comes from a wide area (run-off from agricultural land is an example). Hydro-geologists are scientists who study groundwater by drilling test wells to determine groundwater availability, movement, quantity and quality.
Features on the Ocean Floor
There are several landforms at the bottom of the ocean, some that look like mountains and others look like valleys. An ocean basin is a large underwtaer area between continents. Along the coast of a continent, the ocean floor is called the continental shelf. At this point, the water is shallow but as you go further from the coast, the slope gets sharp. This is called Continental slope.
A submarine canyon is a steep sided valley in a continental slope. These are frequently associated with the mouth of a large river. At the end of a continental slope is another downward slope called a continental rise. Over 40% of the ocean floor is flat. These flat areas are called Abyssal plains. Trenches are the deepest parts of the ocean floor. They are usually long and narrow. A seamount is an underwater mountain that rises from the ocean floor but stops before it reaches the surface of the ocean. Mid-ocean ridges are underwater mountain ranges. An indentation called a rift valley occurs along the top of these mountains.
Ocean Waves
Waves are surface movements 'a disturbance, or variation transferring energy progressively from point to point in a medium' occurring whenever a force comes in contact with water.
Causes of Water Waves
Most waves are caused by the wind (a force). Stronger forces cause larger waves. As ocean waves move closer to the shore their bottoms drag on the ocean floor and their tops rise and break onto the shore (causing damage by their force). Waves begin on the open sea. The smooth waves near the shore are caused by winds and storms far out at sea and are called swells.
Tsunamis
A tsunami (Japanese for harbor wave) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater explosions. In the open ocean, tsunamis move at speeds of 500 to 1,000 kilometers per hour. However, a tsunami slows down as it approaches a shore. The length of each wave decreases, but the height increases. The water piles up, and it is often pulled away from the coastline as the tsunami approaches land. Finally, the tsunami crashes onto the shore as a giant wall of water.
Tides
The water level along the coast of continents changes constantly. This water level is called a tide. High tide is the highest level the water will reach on shore, while low tide is the lowest level it will reach onshore. Usually there are two high tides and two low tides each day. The largest tidal movements are spring tides, whereas the smallest tidal movements are called neap tides. The difference in level between high tides and low tides is called tidal range. What Causes Tides? The gravitational force of the moon and the rotation of the Earth on its axis cause tides.
Surface Currents
Currents of water are driven by winds. There are three factors that influence the direction of winds and surface currents:
1. Uneven heating of the atmosphere (convection)
2. Rotation of the Earth (bending)
3. The continents (deflecting)
Almost all of the heat in the ocean comes from the Sun. Temperature varies throughout the ocean, getting much colder as you go deeper. The temperature of the ocean current not only affects the air temperature, but they also affect the amount of precipitation that an area receives.
Water has a very high heat capacity – meaning it takes a long time to heat up and a long time to loss heat. Large bodies of water act as heat reservoirs in the winter, remaining relative warmer than the nearby land. This difference in temperature can affect the convection currents producing breezes that can alter the processes of evaporation and condensation near the shoreline. A cold current can do the opposite.
Large bodies of water like oceans and lakes have layers or zones. Some organisms live in only one or two zones, while other organisms can live in all three.
Lakes and Ponds
Diversity refers to the variety of different kinds of organism species (both plant and animal) living in a particular ecosystem or environment
Lake Diversity:
| Lake Zone | Zone description | Species that might inhabit this zone |
|---|---|---|
| Upper Zone | The zone of a lake from the shore to where the aquatic plants stop growing | Plants: Bulrushes, water lilies Animals: Small fish, clams, insects, snails, worms, leeches, and frogs |
| Middle Zone | The open water zone that still has light penetration | Phytoplankton are food for fish that live here. Some of the fish that live in this zone also travel to the deeper zones |
| Lowest/Deep Zone | Zone where no light penetrates, so no plants grow there. Food for organisms living in this zone comes from the zones above, in the form of waste. | Deep water fish (large size species) |
Rivers and Streams
Streams and rivers usually alternate between areas where water is calm (pools) and areas where water is moving quickly (riffles). Because of the constantly moving environment, organisms often attach themselves to rocks as their habitat.
Ocean Diversity
Oceans have similarities to lakes in terms of zones, but with greater differences in water motion, salinity and depth, diversity is much greater in the oceans. In summary, the shallow part of the ocean ecosystem is called the intertidal zone. Every day, the pull of the Moon’s gravity causes ocean tides to rise and fall over the intertidal zone. Beyond the intertidal zone is the neritic zone. The key resource in this zone is sunlight. Algae, kelp, and other producers grow in huge numbers near the surface water where sunlight can penetrate. The third zone of the ocean is the oceanic zone. It is divided into the bathyal zone and the abyssal zone. The bathyal zone is home to many large consumers, such as sharks, but few producers. Further down is the abyssal zone, where it gets darker and colder because the sunlight is completely blocked. Organisms in this zone tend to be scavengers or decomposers. They live on nutrients that float down from other zones.
| Ocean Zones | Zone description | Species that might inhabit this zone |
|---|---|---|
| Estuary | One of the most diverse and richest ecosystems. This is where freshwater and saltwater mix to form brackish water | Marshes grow here providing a habitat for many different kinds of plants, insects and other animals that can tolerate the brackish water. These ecosystems are also rich in bird life, because of the abundance of food and shelter available |
| Intertidal Zone | The shoreline of an ocean | Plants and animals living in this zone must be able to withstand the pounding of the waves and the rise and fall of tides. Animals with special adaptations live in this zone. |
| Continental Shelf | Warmer water than out in the deep ocean and this area has full light penetration.. | Many varieties of plants and animals live in this zone because of the rich nutrients available. Phytoplankton are food for fish that live here. Some of the fish that live in this zone also travel to the deeper zone. |
| Oceanic Zone | The zone where very little light penetrates, so no plants grow there. | Food for organisms living in this zone comes from the zones above, usually in the form of waste. Deep water fish (large size species). |
Adaptations for an Aquatic Life
An adaptation is a physical characteristic or behaviour of a species that increases that species' chances of survival in a particular environment.
There are five factors that have led to the development of adaptations by aquatic species.
Temperature: Fish that live in extremely cold water (Arctic) have a natural anitfreeze that keeps their blood and tissues from freezing. Other organisms that live in the very deep parts of the ocean near volcanic vents, organisms can actually survive in extremely hot water.
Light: Plants need light for photosynthesis. In the deepest parts of the ocean some organisms have adapted to the absence of light by producing their own light from spots on their bodies called photophores.
Pressure: As you travel deeper in the ocean, the pressure increases. Those animals that have adapted to different regions of the ocean would be unable to survive in other regions because of the pressure difference.
Salinity: Ocean water has very high salinity levels. Organisms that live in this ecosystem cannot survive in freshwater. Freshwater organisms cannot live in saltwater (think osmosis). Some organisms, can survive in both ecosystems. Salmon can survive in freshwater (where they are born) and saltwater (where they live most of their lives).
Water Movement: Some organisms are able to live in fast moving water. Other organisms are adapted to dig themselves into the sand for protection. Many aquatic animals use the buoyancy of the water to help them move and their streamlined shape in the water reduces drag.
Aquatic Plants
There are two types of aquatic plants: those attached to the bottom and those that float freely in the water (called phytoplankton). Aquatic plants need sunlight and therefore can only survive in water where sunlight can penetrate. Seaweeds are marine plants, that do not have roots, flowers or leaves. They do photosynthesize and use the energy of the sun to create food. Phytoplankton are tiny plants that live on the surface of lakes and oceans and produce oxygen. Their tiny irregular shape, and long spines are adaptations that help them stay in the zone of water where light can penetrate. Diatoms are one example of this type of aquatic plant.
Nutrients in Water
Nutrients are not always abundant in aquatic ecosystems throughout the year. The growth cycle of aquatic plants depends on the availability of sunlight and nutrients (which can be moved by currents, wind, and wave action).
Aquatic Food Chains and Populations
A population is a group of organisms of the same species that live in a particular area.
There are three types of population changes: seasonal, short-term and long-term.
Seasonal Changes - There are dramatic changes in populations of freshwater organisms between the seasons such as changes observed in northern regions (Canada) because of extreme temperature changes. Populations swell in the summer and disappear in the winter. During the winter, surviving individuals may be dormant, or hibernating. Breeding cycles can also cause seasonal changes in populations.
Short-Term Changes - Short-term changes take place over a relatively short period of time and don't last very long. They happen irregularly and may be part of a natural event, or caused by human activities. El NiÑo is a natural event that might adversely affect fish populations.
Long-Term Changes - Long-term changes in populations also result from natural events or human activities. These changes can cause ripple effects because of the interactions that occur within every ecosystem.
Toxins In Aquatic Habitats
Residues from pesticides, fertilizers and industrial chemicals can find their way into the water system. When this happens, the concentrations of these toxins can be magnified as they move up the food pyramid. This is called biomagnification. Animals that have a large amount of fatty tissues are highly susceptible to the toxins effects. This is because the toxins are stored in the fatty tissues.
Fishing
Fishing can affect the balance of fish populations. Over-fishing, specialized fishing, introduction of new species and pollution can all affect the fish populations. When the population of specific species of fish are modified by any of the reasons above, the populations of other species will also be affected within the same ecosystem.
Water contains dissolved solids (salts such as sodium, calcium and magnesium). If it contains a lot of calcium and magnesium it is called hard water, whereas soft water contains less. Hard water can cause scaly deposits in pipes, fixtures and appliances
Throughout the world, water is recycled through the water cycle but this doesn't mean that every area in the world will have the same amount of water. No one area can expect the same amount of water year after year. People are also part of the water cycle.
There are direct (domestic or personal use) and indirect (industrial and agricultural) ways that humans use water. Many of these indirect uses can have negative effects on Earth's water supply.
Runoff from farmland may contain fertilizers, manure or compost that can cause excessive plant growth. It may also contain toxic chemicals (pesticides and herbicides) that can kill living organisms.
Some industries can discharge warm water into lakes or rivers causing thermal pollution, which can kill organisms that cannot tolerate the increased temperature. Industrial discharge can also contain toxic chemicals with unpredictable effects such as tumors, birth defects, sterility and even death or organisms.
Sewage contains large amounts of nitrogen, which causes micro-organism populations to increase, using up most of the oxygen and creating zones of low oxygen which affects other organisms causing death.
Oil Spills can cause harm to plants and animals in, on or near the water.
Measuring Water Quality
Below are several factors that can be measured to assess water quality:
The diversity of aquatic organisms in a water system helps to indicate the quality of the water. The level of dissolved oxygen will determine which species will be able to survive and, which ones will perish. High levels of dissolved oxygen would likely see a vast diversity of aquatic organisms. However, not all of these species are positive indicators, because some micro-organisms can cause disease and death.
Monitoring Water Quality: Water systems everywhere need to be monitored and cleaned up if they are causing a problem. One way to help guard against problems with water quality is to monitor the water supply. To monitor means to observe, check, or keep track of something for a specific purpose. Town and city water supplies have to be monitored on a regular basis to ensure that the quality of the water remains high.
Water Management: Maintaining a reliable and safe water supply is called water management. To make water safe to drink, or potable, for humans it has to be treated. The treatment of water involves screening, mixing, sedimentation, filtering, and adding chemicals. After water has been used by humans, the solid and liquid waste (sewage), has to be treated again before it goes back into the water system as effluent. In rural areas an underground treatment system for this sewage involves using a septic tank. Three additional processes are used to increase the potable water supplies in different parts of the world. Desalination (removing salt from water) Distillation and Reverse Osmosis.
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