Students in Grade 5 learn more details about the cell and how different cells have different functions and form the basic units of various organs in the body. Students will also develop a deeper understnding of the relationship between different living things and their environment, and how living things can affect their environments positively or negatively. In this regard, students will learn the importance of biodiversity and how groups of living things form ecosystems.
All living things are made up of cells. A cell is the smallest unit of living matter that can carry out the basic functions of life.
Cells reproduce through cell division, Cell division is where one cell multiplies into two cells and the process continues until a different (regulatory) process reduces the rate of cell division. This way the number of cells increases. Some cells also die in the process. Each cell that you observe came from another cell.
A Unicellular organism is made up of only one cell that can independently carry out life functions.
A Multicellular organism is made up of multiple cells. Humans, frogs, insects are all multicellular organisms.
Cells in multicellular organisms are capable of specializing. Specialzing is a simple way of indicating that cells can develop the ability to perform specific functions.
Cells of the same type (and function) are grouped together to form tissues. Tissues can also group together to form an organ. An organ is a group of tissues that perform a function. For example, the heart is an organ and its function is to pump blood. Many organs work together to form an organ system. The heart, together with blood, and blood vessels make up the circulatory system whose function is to pump and distribute blood to all parts of the body.
Scientsists estimate that there are more than 1 billion kinds of organisms, most of which not yet even been identified.
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.
Multicellular organisms are made up of multiple cells, that perform different functions, intially forming tissues. Several tissues come together to form organs. For example, the heart is an organ. Several organs can function together to form an organ system. For example, the circulatory system is an organ system. Its made up of the heart, blood vessels and blood. Many systems work together to make an organism.
All plants need air, water and sunlight. Plants can obtain air and sunlight directly from their environments. Water transport within the plant requires more complex processes.
Plants can be classified into two types, depending on how they transport water. Non-vascular plants are small and survive without a water transport system. Mosses, for wxample, reach heights of a centimeter or less, their parts are so close to the ground and they can absorb water directly. Vascular plants are larger can grow to heights over 60 meters. Larger trees have a vascular system, which is a series of hollow tubes. These tubes can transport water and nutrients to the top of the tallest trees.
Vascular plans are further divided into seed and seedless plants. seed plants indicate that they are flowering plants and produce seeds. A seed can develop into a plant when the environmental conditions are favorable. Seeds have a a protective coating that prevents the seed from drying out or getting damaged. Seedless plants, like ferns, produce spores for reproduction. A spore is a single cell that can develop into a new plant exactly like the plant that produced it.
There are two main types of seed plants: gymnosperms and angiosperms. A Gymnosperm is a seed plant that does not produce a flower. These include pines, firs and other cone- bearing trees. An Angiosperm is a seed plant that produces flowers. All angiosperms produce seeds that are covered by some kind of a fruit. In some angiosperms, the fruits a more obvious, such as apples and peaches et cetera. In other angiosperms, the fruits are less distinct, such as grasses. There are over 250,000 different kinds of angiosperms making this group one of the largest of its type.
Roots: A root is the part of the plant that absorbs water and minerals, stores food and anchor the plants to the ground. Roots absorb water using fuzzy hairs called root hairs. A root hair is a threadlike projectiong from a plant root. Each root hair is less than 1mm in length but together they soak up moisture like a sponge.
The outer layer of a root and the whole plant is the epidermis. The epidermis is where the root hairs are located. The cortex layer is located just under the epidermis. It is used to store food and nutrients. The vascular system is located in the center of the root. This system transports water and minerals absorbed by the root hairs.
Different plants have specialized roots for their environment.
Aerial roots are roots that never touch the ground. They anchor the plant to surfaces or to other trees and they absorb water from the air and from rain, not from the soil.
Fibrous roots are thin, branching roots that do not grow too deep into the ground but they cover a large area. A single clump of grass has over 600km of fibrous root.
Taproots have a single stalk-like root that plunges deep into the ground. Several smaller roots branch off of the main main taproot. Pine trees and trees that grow in dry areas often have taproots.
Prop roots usually grow at the bottom of a plant's stem. They prop up so as to prevent the plant from being knocked over. Corn/maize plants and mangrove trees have prop roots.
Stems: A plant's stem has two functions, as a support structure and as a transport system for the plant. The stem supports the tree's leaves, flowers, fruits and other parts. Stems can either be soft or woody. Soft stems, like those found in grasses, can easily bend. They are usually green because they contain chlorophyll and can produce food for the plant. Shrubs and larger trees have woody stems, which are covered with bark. The bark is a tough outer covering that serves as a protective layer. Woody stems do not contain chlorophyll.
The transport system in the stem actually begins in the root. There are two kinds of cells that make up the system. Xylem is a series of tubes that move water and minerals up the stem. Transport through the xylem only happens in one direction, away from the roots to the leaves. Phloem moves sugars that are made in the leaves to other parts of the plant. Phloem tissue is a two way transport system. For example, in carrots, sugars are transported down to the root. The phloem tissue also transport sugars up from one part of the plant to another. The layer that separates the xylem and phloem tissue is called the cambium.
Leaves : The most important function of the leaves is to carry out photosynthesis. Cells within the epidermis make up the plant's main food factory.
To perform photosynthesis, plants need sunlight, water and carbon. Many leaves are flat and wide to enable them to collect the most sunlight.
Water enters the plant through the roots. The top part of the leaf has a shiny/waxy cuticle which prevents water loss through evaporation.
Leaves get carbon dioxide from the air. Air enters the leaf through areas of the leaf called Stomata (one is called stoma). Each stoma is surrounded by Guard cells. When the guard cells swell, they open the stomata and allow water to leave the leaf. When the plant is low on water, the guard cells shrink and close the stomata and prevents the loss of water.
The loss of water through the leaves is called Transpiration.
As water evaporates through the leaves, more water is carried by the tree from the roorts and moves into the leaf, replacing what was lost.
Carbon dioxide enters the leaf and through a series of reactions with water, in the presence of sunlight energy, produces sugars (C H O). The sugars are transported to other parts of the plant to support life processes. Excess sugar is converted and stored as starch. This photosynthesis process produces oxygen as a by-product, which is why we say that plants are important to remove carbon dioxide from the atmosphere and add oxygen.
The sugars produced during photosynthesis are used by most organisms for energy. The energy is released when the cells of organisms use oxygen to break down the sugars stored as starch in the process of cellular respiration.
During cellular respiration, plant and animal cells produce carbon dioxide and water as waste products, which are then released back into the air. Plants use the released carbon dioxide and water to produce sugars during photosynthesis.
We begin to study Animals in more details in Grade 5. We will start with the group of animals called Invertebrates.
Invertebrates are animals that do not have a backbone (vertebrae). They can live on land and in water. Most lower invertebrates live in aquatic environments (in water). Lower invertebrates include sponges, cnidarians and worms.
Sponges are the most simple of all animals. They have no true organization. They do not have real tissues or organs. They are also asymmetrical, which means, their body cannot be dividied into mirror images. Their body is organized around a single tunnel like cannal and the tissue surrounding the canal has many pores (holes). All sponges live in water. Sponges filter the food out of the water that goes in their pores. The 'filtered' water then exits through the osculum.
Jelly fish, sea anemones, hydras and corals are all cnidarians. Unlike sponges, cnidarians have radial symmetry, which means all the body parts are arranged around a central point. Organisms with radial symmetry have more than one line that divides the organism into two mirror images. Cnidarians have a mouth, tentacles, muscle tissues, and stinger cells. When they hunt, their stingers shoot out like tiny harpoons. The poison inside these cells helps them capture other animals.
Worms can be divided into three main groups:
All worms have bilateral symmetry, which means their body can be divided along only one plane to produce two mirror images.
Flatworms are calso called Platyhelminthes. They have a flat body and a head with simple eyes and mouth. They have one opening which acts as a mouth, but also undigested food waste also leaves the body through the same opening.
Roundworms are also called Nematodes. They have a simple digestive and nervous systems. They are some of the most abundant animals on the earth. They often live inside the body of other animals.
Segmented worms are also called Annelids. They have a body plan that is divided into segments. Unlike flatworms, segmented worms have two openings, and they also have organs including a stomach, heart and brain.
Invertebrates are a very large diverse group of animals and live in many diverse environments. As you already read that some are developed only to a rudimentary degree, while some are more advanced, with multiple body openings, some organs etc. Some invertebrates have specialized organs and complex body structures. These include Mollusks, Echinoderms and Arthropods.
All mollusks share the same body plan. They have a muscular foot or tentacles, a fold of tissue called the mantle and a mass of internal organs. They are all bilaterally symmetrical. They include snails, clams, and squids. Almost all mollusks have a shell, which is secreted by the mantle. Mollusks have several specialized organs including a heart, gills for breathing and a well developed nervous syetm.
Echinoderms include sea stars (star fish), sea cucumbers and sea urchins. They have a hardened skeleton located inside the body called Endoskeleton. Echinoderms use water pressure to feed, breath and move. Sea water enters the system and moves to different parts of the body under pressure. The system ends in the tube feet which cling to surfaces like sunction pumps.
Arthropods are the most numerous animal group on earth. More than half of the world's animal spcies are arthropods. They are small and have a skeleton on the outside (exoskeleton). All arthropods have bilateral symmetry. Arthropods have a segmented body with paired limbs on either side of the body. These limbs are used as wings or claws. Arthropods have a simple but very efficient nervous system.
Vertebrates are animals that have a backbone (a vertebrae). They all have an endoskeleton and are bilaterally symmetrical.
There are three classes of fish:
Jawless fish include Lamprey and hagfish. They have a flexible nerve cord and because they do not have jaws, they obtain food by sucking.
Sharks, skates and rays are cartilaginous fish. Their skeleton is made of cartilage rather than bones. Cartilage is the material that make your ear stiff, its not as hard as bone. These fishes also have paired fins amd jaws.
Bony fish have a nerve cord covered by bone, not cartilage. They have jaws and paired fins. They have ballonlike swim bladders that allow them to easily go up and down in the water. They also have moving flaps that push water into their gills where they obtain oxygen while not moving in water.
Frogs and salamanders are amphibians. They spend parts of their life in water and part in land. A frog begins its life in water as a tadpole with gills. As it matures, the frog develops four legs and lungs for breathing air. Most adult amphibians do not leave the water for too long. For example, most frogs can breath through their lungs, and also through their skin so they stay moist at all times. They also lay their eggs in water.
A reptile is a true land animal with one or two lungs. They have a thick scaly waterproof skin. They include lizards, snakes, turtles, alligators and crocodiles. Reptiles are cold blooded animals, which means they cannot generate much body heat. They stay warm by exposing themselves to the sun and making use of the heat in their environment. This means they cannot keep their body temperature stable.
Birds have several features that make them different from other vertebrates. They have two legs and two wings. Birds have hollow bones to reduce their weight and enhance flight.
The unique feature of birds is the presence of feathers. They are strong but also light. Feathers help keep the bird warm and enable the birds to keep their body temperature steady. Feathers also assist in flight because they are smooth and point backwards reducing the resistance and drag.
The word mammals is derived from the word 'mamma', which means teat/pap. Mammals are characterized by the presence of milk-producing mammary glands for feeding their young. Mammals also have a big brain and hair or fur. Tehy generate their own body heat and are able to maintain a constant body temperature within a range of environmental temperature.
Mammals are divided into three groups (subclasses):
Living things depend on each other. They also depend on nonliving things like sunlight. Living and nonliving things that interact in an environment make up an ecosystem. An ecosystem may be a pond, a swamp, or a field, maybe large or small.
Different organisms live in different parts of an ecosystem. Fish live in the water, so the water is the fish's habitat.
A food chain shows how energy passes from one organism to another in an ecosystem. When a buffalo feeds on grass, they obtain energy from the grass, and when a lion feed on the buffalo, they obtain energy from the buffalo. energy flows from grass to buffalo to lion.
The first organism in a food chain is called a producer, these are organisms that make their own food. Green plants are examples of producers. Most producers use energy from the Sun to make their own food. This means that the energy in most food chains starts with the Sun.
A consumer is the organism that eats other organisms. All animals are consumers. A food chain may have many consumers.
Organisms that eat mostly plants are herbivores. Some animals, such as herons, eat mostly other animals. These organisms are carnivores. Animals that eat both plants and animals are omnivores.
Predators hunt other organisms for food. The organisms they hunt are prey.
A decomposer is an organism that breaks down dead plant and animal material. Decomposers put nutrients back into the soil. Some worms and bacteria are decomposers.
Since consumers can eat many types of organisms, many food chains can join to form a food web.
Plants produce their own food.
Herbivores eat plants.
Carnivores eat other animals.
Omnivores can consume both plants and animals.
Decomposers utilize dead and decaying matter into waste and simpler substances.
Plants are called producers because they produce their own food. Animals are called consumers because they eat, or consume, other living things. Plants are essential to ecosystems because they produce the food which all other living things need. To represent how living things feed off other living things in an ecosystem, we can use a food chain.
Competition: Sometimes living things have to compete to get what they need. This is called competition. Predators compete with each other. For example, lions and cheetahs hunt the same herbivores. Plants in a forest compete for sunlight.
Cooperation: When living things help each other to survive in an ecosystem, this relationship is called cooperation. For example, a tree may provide a home for a bird's nest. Bees can pollinate flowers.
Energy Pyramid: Whenever we consume food, we do not use up all the energy available in that food. Some of it is wasted. For example, plants use the energy from the sun to produce their food. However, when herbivores and omnivores eat the plants, they cannot be able to extract all the energy. In fact, only about 10% of energy is transferred from one level of the food chain/web to the next. An energy pyramid is a representation of the energy transferred from one level of the food chain to the next, with producers at the base of the pyramid.
All important resources in an ecosystem are scarce, as in there is less than the ecosystem needs to survive. This includes resources like water, food, space and other resources. The fight for these resources is called competition. For example, a fox will compete with other foxes to catch rabbits. Competition can also occur across different kinds of animals. For example, foxes also compete with hawks for rabbits. The rabbits compete with other herbivores for the food.
A limiting factor is any resource that restricts the growth of populations. A forest gets more rainfall and much warmer in summer than in winter. In summer, the forest can support many more organisms than in winter. Limiting factors may also include abiotic factors. Abiotic factors are non-living factors, such as water, temperature, soil type, shelter, sunlight and others.
Carrying capacity is the largest number of individuals within a population that an ecosystem can support. As the population increases, the food becomes harder to find and some of the individuals die to the level where there is an equilibrium where there is just enough individuals to survive successfully in the ecosystem.
Overcrowding (limited space) can also limit growth. A population of algae in a pond or bacteria in a petri dish will eventually become too thick that they exhaust the resources in the space such as oxygen. Without sufficient resources, the algae begin to die off.
We can define a habitat as the physical place where an organism lives and finds its food. Some individuals have small habitats like some bugs may spend almost their entire life under a rock. In some cases, an individual's habitat can be large. For example, a bee may occupy a large habitat where it goes around obtaining nectar.
A niche is the special role that an organism plays in a community. Two birds might live in the same location and eat the same food, but one bird is active at night, the other is active during the day. Or two birds might be in the same habitat but eating different food. Multiple animals can live in the same tree but some may be at the tallest tip of the tree and others may live closer to the ground.
Living things depend on each other for survival. They establish interlocking relationships. This relationship is called Interdependence. Symbiosis is the terminology used to define a relationship between two or more kinds of organisms that lasts over a period of time.
Mutualism is a symbiotic relationship where both organisms benefit and neither is harmed. The relationship between pollinators and flowers is a good example. Pollinators such as bees obtain food (nectar) from the flowers while the flowers obtain pollination.
Commensalism is an interelationship between two organisms where one organism benefits from the other, but it does not cause harm to the other.
Remora are fish that attach themselves to the bodies of rays and sharks. The remora gets food scraps, transportation, and protection from the ray. What does the ray get from the remora? While the remora does not hurt the ray in any way, it does not help the ray either.
Sometimes its difficult to be sure whether an organisms is benefiting from a relationship or getting harmed by the relationship.
Parasitism is a symbiotic relationship where one organism benefits and the other is harmed. The individual that benefits is called a parasite. The organism that gets harmed is called the host. A parasite may live ON or IN the host. For example, ticks are parasites to dogs, cattle, goats and many other animals. A tick attaches on the host, feeds on on the host's blood and may sometimes transmit diseases to the host. Tapeworms are parasites in the digestive system of humans and some other individuals.
We have mentioned that resources in an ecosystem are usually scarce and individuals within that ecosystem have to compete for those resources. An adaptation is any characteristic that helps an organism survive in its ecosystem. The offspring inherit these adaptations and so they are also able to better survive in the ecosystem.
Adaptations can be structural or behavioral.
Structural adaptations are adjustments to physcial structures on the organism. For example, it could be fur color, strong jaws, the ability to run very fast, having a long neck etc. Cactuses have a thick waxy cuticle that prevents water loss in their dry environment.
Some individuals change their behavior to be able to survive in the ecosystem. For example, wolves travel in packs, this way they can hunt more successfully. Some fish swim in groups (called schools), which protects them from predators. Some behaviors help animals survive different climatic conditions in their ecosystem. Some animals move (migrate) to find food, water and a less severe climate. Other animals such as snakes, turtles, frogs etc hibernate to escape the cold. Hibernation is when an animal drastically reduces its activity and as a result, its metabolism, as a way to conserve energy during cold winters, and resumes normal activity when temperatures improve in Spring.
Plants also have many adaptations to survive in their environments. Some have scented flowers to attract pollinators. Some aquatic plants, such as water lilies, have stomata on the top surface of the leaf instead of the bottom. This enables the stomata to take in and release carbon dioxide and oxygen.
Desert animals are often nocturnal, which means they are active at night when the temperature is cooler. During the day, these animals stay in underground burrows to avoid the heat.
Camouflage is any coloring, shape, or pattern that allows an organism to blend in with its environment. Predators with camouflage can sneak up on prey. Camouflage also helps prey animals hide from predators.
Protective coloration is a type of camouflage where the color of an animal helps it blend in with its background. In winter, the arctic fox has a white coat that blends in with the snow. In summer, the foz's coat changes color to blend in with plants that grow in the warm weather.
Protective resemblance is when the organism combines multiple mechanisms such as protective coloration, shape, texture etc to resemble the environment.
Some animals have adapted to their environment by copying other well-adapted organisms. An adaptation in which an animal is protected against predators by its resemblance to an unpleasant animal is called mimicry. The example below shows a coral snake that is poisonous and a milk snake that is harmless. The milk snake mimics the coloration of the coral snake so it will also appear to be poisonous.
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.
Carbon is one of the most important elements in every living thing. About 18% of the body is Carbon. Carbon is also plentiful in the atmosphere in form or carbon dioxide CO2 gas. Carbon is also present in rocks (as limestone).
Carbon is exchaned continously between the different sites and chemical forms. Plants take up carbon dioxide from the air to fulfill their photosynthetic needs and produce sugars (remember sugars are made of C H and O). These carbon rich compounds are then eaten by herbivores (like cattle, sheep, deer, rabbits) and omnivores (such as humans). The herbivores and omnivores use the carbon rich compounds from plants to make their own carbon rich compounds such as proteins, sugars and fats. Herbivores and omnivores are then consumed by carnivores enabling the transfer of these carbon rich compounds to all different levels of the food chain. Living organisms can also transfer their carbon when they die and decompose. In such cases, the carbon may be transferred to the soil, or maybe used by decomposers such as bacteria and fungi. The breakdown of carbon compounds by decomposers releases carbon to the environment as methane, carbon dioxide, or other carbon compounds. After millions of years, the carbon that remained in the ground will turn into fossil fuels such as coal, oil and natural gas. These will be harvested/mined by humans and brought back into the atmosphere through their use in cars, heating homes or cooking. All these processes result in the formation of carbon dioxide which goes back into the atmosphere. Plants remain the most significant users of atmospheric carbon dioxide so it is important to ensure there are many trees to avoid too much increase in the levels of atmospheric carbon dioxide. Ofcourse, it is also important to reduce the release of carbon dioxide into the atmosphere.
The air is 78% nitrogen gas. Nitrogen cycles through both the abiotic and biotic parts of the Earth system. The largest reservoir of nitrogen is found in the atmosphere, mostly as nitrogen gas (N2). Nitrogen gas makes up 78% of the air we breathe. Most nitrogen enters ecosystems via certain kinds of bacteria in soil and plant roots that convert nitrogen gas into ammonia (NH3). This process is called nitrogen fixation. A very small amount of nitrogen is fixed via lightning interacting with the air. Once nitrogen is fixed, other types of bacteria convert ammonia to nitrate and nitrite, which can then be used by other bacteria and plants. Consumers (herbivores and predators) get nitrogen compounds from the plants and animals they eat. Nitrogen returns to the soil when organisms release waste or die and are decomposed by bacteria and fungi. Nitrogen is released back to the atmosphere by bacteria get their energy by breaking down nitrate and nitrite into nitrogen gas (also called denitrification).
Natural events include natural disasters and changes caused by organisms. Earthquakes, floods, storms, volcanoes, droughts, and other natural disasters can drastically alter ecosystems. People can try to repair the damage from these disasters, but there is little or nothing anyone can do to prevent such events from occurring. The second type of natural change is caused by organisms. Large animals, like elephants, can cause changes by trampling trees and seedlings. Humans cause ecosystem changes by shaping the environment to meet their needs. These changes often destroy or alter habitats and affect the organisms that live in those habitats. Humans also change ecosystems by introducing new species or removing species. Introduced plant and animal species can threaten native species.
Some ecosystem changes are permanent. Organisms must respond to changes in order to survive. Organisms that cannot respond to ecosystem changes begin to die. When the last member of a species dies, the species becomes an extinct species. Some extinct organisms include all species of dinosaurs, mammoths, the saber-toothed cat, and many others.
The Tasmanian wolf, for example, became extinct about 65 years ago as a result of human actions. These wolves once lived in Australia. Farmers saw the Tasmanian wolf as a threat to their livestock and hunted the animal to extinction.
Pollution, global warming, habitat destruction, and hunting can also threaten the survival of organisms.
Below are examples of extinct animals, the first is the Tasmanian wolf and the second is the Saber toothed cat.
When a species is in danger of becoming extinct, it is called an endangered species. The flying squirrel is an example of an endangered species. Usually, only a few hundred individuals of the species exist.
Species with low numbers that could become endangered are called threatened species. The gray wolf, the manatee, and many others are threatened species.
Over time, an ecosystem can change to a new type of ecosystem, this change is called Succession. There are two kinds of succession:
Primary succession occurs where there are few living things that exist, or where the earlier community was wiped out. Primary succession occurs in barren, lifeless areas that have little or no soil. Particles of soil and seed blow from neighboring environments and lichens and mosses start to grow. In this case, the first organisms that begin to grow in the area are called Pioneer species. If there are multiple species that grow first in an area, this can be described as a pioneer community. As more plants grow, the soil quality and nutrients improve, the soil becomes more suited for even more plants and some animals. grasses, ferns, shrubs begin to sprout. Flowering plants attract pollinators to the area, such as insects, birds, and small mammals. These animals attract larger predators to the community. After many years, this community may become a grassland or prairie. A climax community is the final stage of succession. Unless the community is disturbed by some natural disaster or human activity, the climax community will remain.
Secondary succession is where a new community develops in a place where another community already exists. Secondary succession can occur in a forest after a fire has occured. Secondary succession utilizes soil that already has the nutrients and factors needed for good plant growth. For example, when a farm is abandoned, weeds begin to grow and after a couple of seasons, shrubs also begin to grow.
A biome is one of Earth’s major land ecosystems with its own characteristic animals, plants, soil, and climate. A climate is an average weather pattern for a region. How is a biome different from other habitats? You can think of a biome as a set of habitats or ecosystems all grouped together into a kind of 'super-ecosystem.'
There are 5 major land biomes:
Aquatic biomes include both freshwater and marine biomes. Freshwater biomes are bodies of water surrounded by land—such as ponds, rivers, and lakes - that have a salt content of less than one percent. Marine biomes cover close to three-quarters of Earth’s surface. Marine biomes include the ocean, coral reefs, and estuaries.
Grasslands are open regions that are dominated by grass and have a warm, dry climate. There are two types of grasslands: tropical grasslands (sometimes called savannas) and temperate grasslands. Savannas are found closer to the equator and can have a few scattered trees. They cover almost half of the continent of Africa, as well as areas of Australia, India, and South America. Temperate grasslands are found further away from the equator, in South Africa, Hungary, Argentina, Uruguay, North America, and Russia. Prairies are types of temperate grasslands; prairies are characterized as having taller grasses.
Forests are dominated by trees, and cover about one-third of the Earth. The three major forest biomes are temperate forests, tropical forests, and boreal forests (also known as the taiga). Tropical forests are warm, humid, and found close to the equator. Temperate forests are found at higher latitudes and experience all four seasons. Boreal forests are found at even higher latitudes, and have the coldest and driest climate, where precipitation occurs primarily in the form of snow.
Deserts are dry areas where rainfall is less than 50 centimeters (20 inches) per year. They cover around 20 percent of Earth’s surface. Deserts can be either cold or hot, although most of them are found in subtropical areas. Because of their extreme conditions, there is not as much biodiversity found in deserts as in other biomes.
A tundra has extremely inhospitable conditions, with the lowest measured temperatures of any of the five major biomes with average yearly temperatures ranging from -34 to 12 degrees Celsius. They also have a low amount of precipitation, just 15–25 centimeters per year, as well as poor quality soil nutrients and short summers. There are two types of tundra: arctic and alpine. The tundra does not have much biodiversity and vegetation is simple, including shrubs, grasses, mosses, and lichens. This is partly due to a frozen layer under the soil surface, called permafrost.
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.
Marine Ecosystems: 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.
The boundary where fresh water feeds into salt water is called an estuary. Estuaries are unique ecosystems that are part salt water and part fresh water. Like intertidal zones, estuaries change with the tides. When the tide comes in, estuary water becomes more salty. The tide also brings in nutrients from the land. Many ocean fish return to estuaries to lay their eggs. Countless insect larvae, young fish, and tiny crustaceans begin their lives in the calm, protected waters within an estuary. Larger organisms, including egrets, herons, frogs, turtles, muskrats, raccoons, otters, and bobcats feed on these smaller consumers.
A landform is a physical feature on Earth's surface. Each landform has specific characteristics and each landform forms in a different way.
Land Features
Water Features
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.
Mapping Earth's Features
Mapping the features on the earth surface requires several peopple with different expertise. Surveyors are people who measure the land. As the first step in making a map, a surveyor measures the elevation in a specific location. Elevation indicates how high the ground is above sea level (height above sea level). Mapmakers then use the surveyor's measurements to show changes in elevation on a map. The various elevations can be shown on a map using different shades of colors. This gives a 3D appearance on a 2D paper. Maps that use variation in shading to indicate elevation are called relief maps.
A map that uses lines to represent elevation is called a topographical map. each line is called a contour line and it represents a different elevation. Some lines might have numbers on them, these numbers represent the elevation, either in meters or feet. Contour lines that are close together mean that section is steep, as compared to contour lines that are farther apart.
The Earth's Layers
The air around you is the Earth's atmosphere. The atmosphere includes all of the gases around Earth. All of Earth's liquid and solid water, including oceans, lakes, rivers, glaciers, and ice caps, makes up its hydrosphere. The hydrosphere covers approximately 70% of the Earth's surface.
Like an egg, Earth has several layers. The continents and ocean floor make up Earth’s outermost layer, called the crust. The crust is Earth’s thinnest and coolest layer. The layer below the crust is the mantle. Part of the mantle is solid rock. Part is nearly melted rock that is soft and flows. It is a lot like putty. At the center of Earth is the core. The core is the deepest and hottest layer of Earth. The outer core is melted rock. The inner core is solid rock. The biosphere means the parts of Earth where living things are found. Organisms have been found from the atmosphere to the ocean floor.
Soil is a mixture of minerals, weathered rocks, and other things. It has bits of decayed plants and animals called humus. So we can define soil as consisting of organic and inorganic material. Organic material are those coming from or having to do with living things, such as decaying plant and animal material. Inorganic materials do not come from living things, such as minerals and weathered rocks.
The making of soil starts with weathering. Weathering causes rocks to break down into smaller and smaller pieces. The tiny bits of weathered rock build up into layers.
Soil Layers / Horizons
Generally, soil can be divided into three horizons; A, B and C.
The A horizon contains most of the nutrients and humus. The nutrients in the humus are used by plants to grow. In addition, the humus absorbs water and keeps it for a longer period of time and releases it to plants. The soil in this layer is called topsoil.
The horizon B is called subsoil. This layer contians less humus and more particles of rocks.
The C layer is mostly made of larger pieces of rocks. This layer sits on solid unweathered rock called bedrock.
Different places have different depths of each soil layer, and some areas may even lack one of the layers totally.
Soil in different places has different properties and each type of soil has different amount of nutrients and can support different plant and animal life. The soil in a forest has a thin layer of humus and topsoil. Frequent rains carries minerals deep into the ground. Crops with shallow roots do not grow well in such environments because their roots cannot reach the minerals. Desert soil is sandy and does not contain much humus. Because of the sarce rains in the desert, plants here have special adaptations to survive. Desert soil, however, is rich in minerals because they are not washed away by rain water. Plants may grow in deserts if they are supplied with water artificially (irrigation). The grasslands are good for crops such as wheat, rye and corn. The soil is rich in humus, which provides nutrients for the plants. Animals feed on the grasses and also drop their waste on the ground, which adds to the organic matter.
Soil is a resource that can be wasted through processes like erosion. Plants roots help to keep the soil aggregated and prevents erosion. Plants obtain nutrients from the soil as they grow, and they replace them when they die. If farmers remove all crops from the land, they are removing the nutrients from the land and over time the land becomes less able to support new crops.
Pollution
Pollution is the addition of harmful materials to soil, air or water. Soil can be polluted by chemicals such as those used to kill insects and weeds. Garbage that cannot decay, such as plastic contianers, can also pollute the soil if they are dumped.
Soil Conservation
Conservation generally refers to practices that protect and preserve natural resources. There are several ways of conserving soil including:
Fossils are the remains of ancient organisms preserved in soil or rocks. When an organism dies and are covered in soil, sand or other sediments, the sediments harden over and around the organism's remains. Almost all fossils are found in sedimentary rocks. Scientists can study fossils to understand the characteristics of organisms that lived many years ago. These characteristics may also be used to determine the environmental conditions that were present many years ago.
Fossil fuel is a material that formed from the decay of ancient organisms and is used as a source of energy. For example, decayed parts of ocean organisms were buried deep under the ocean. There, a combination of the weight of rock, heat, and the action of bacteria turned the decayed materials into oil and natural gas. Oil and natural gas also are fossil fuels.
Scientists can estimate the age of fossils by observing the layers of the sediments. Fossils found on the top layers are more recent, were deposited more recently, than fossils found deeper in the sediments. This is called relative age. The word relative, means it has been estimated in comparison to something else. The Absolute age of a fossil is the actual age in years. It can be estimated by estimating the age of the rock layer where the fossil was found. The age of the rocks is estimated by the amounts of various elements. The concentration/amount of certain elements reduces at a contant way. For example, lets say it takes 1 million years for half of element A to change into Element B. After 1 million years, the rock contains equal amounts of element A and B. This time point is called an element's half-life. As mentioned, during the first half life, you will observe equal amounts of Element A and B. During the second half-life, more Elemebt A will be converted to Element B, so by the 2 million year mark, there will be 75% of element B and 25% of element A. at the 3 million year mark, there will be 87.5% of element B and 12.5% of element A. Notice that at every subsequent half-life, the concentration of element A is halfed. Different elements different half-lives.
Using the relative age of fossils and rocks, scientists estimated that the age of the earth is around 4.6 billion years. during those 4.6 billion years, there has been several eras. An era is a unit of time measured in millions of years. Geological periods divide eras into shorter periods of time where specific major geological events occured.
Fossil fuels can be burned to release energy. For example, gasoline is used to make cars move. Natural gas is used to heat homes in parts of the world that experience cold seasons. Many homes use electricity to run devices and power appliances etc. Electricity is generated in power plants from generators and the electricity is then 'transported' through wires to the places where it is used.
Approximately 70% of the Earth's surface is covered with water. However, because most of this water is in oceans, it is salty. In fact, 90% of the earth's water is salty. About 2.5% of the Earth's water is frozen at the North and South poles. About 0.1% of the water is in the air as water vapor. Only 0.6% of the Earth's water is fresh liquid water. Many living things utilize the fresh water to survive. Most of the fresh water is obtained from running water, standing water and groundwater.
Running Water
Many cities are built close to sources of running water such as rivers or streams. running water is a source of fresh water for homes, businesses and farms.
Standing Water
Standing water includes bodies of water such as lakes and reservoirs. A reservoir is an artificial lake built to store water. Reservoirs are usually made by building a dam across a river. The water is stored behind the dam and is released when needed.
Groundwater
Water seeps into the ground through aquifers. An Aquifer is an underground layer of rock or soil that has pores and is capable of absorbing water. When the seeping water reaches a layer of rock that does not have pores, it settles there builds up and can be used by humans by drilling or digging into the ground. Once ground water has been harvested, more water must seep from the surface so as to replace the ground water again.
Some countries/regions use water for irrigation. Irrigation is supplying water to agricultural farms by artificial means.
The water used in most homes is supplied by a water company. The water usually undergoes some treatment processes then pumped through pipes into homes and businesses. Some homes may use well water. A well is used to obtain groundwater by drilling and installing a pipe deep into the ground and pumping water to the surface. This water may undergo treatment and then used for human consumption. Otherwise, well water may also be provided to farm animals.
Drinking water should be free from contamination. You should be on the look out for possible contamination in water, such as a change in color (fresh water should be clear), visible dirt in the water, any smell in the water (fresh water should not have any smell - odorless).
The water that runs in most homes is usually treated in a water treatment plant to remove contaminants. Water is first obtained from a fresh water source such as a reservoir or a lake and then it is run through several tanks, with each tank having a different function. The steps may vary with there the water was obtained from.
The first step is to remove dirt through a process called coagulation. This involves the use of sticky particles to attract the dirt.
The next step involves sedimentationwhere clumps of dirt and the sticky particles sink to the bottom of the tank.
The water then is passed through a series of filters made with layers of sand, gravel, and charcoal. These remove more particles from the water. Afte this tank, chlorine is added to the water to kill harmful bacteria. This step is called disinfection. The clean water is stored in tanks until it is pumped to homes and businesses.
Water conservation refers to all efforts made to reduce the waste of water. This may be targeting a small scale level at the individual level, like showering for a shorter time. Conservation can also be aimed at a larger scale, like a lake or a watershed.
Water protection involves the use of government regulations to limit the uses of water. For example, a government may restrict the use of water to domestic uses only and regulate the use of water for irrigation such as watering the lawn.
The Earth's atmosphere holds the gases that living things need to stay alive. You cannot see air (its invisible), you cannot smell air (its odorless) and if air is not moving, you cannot feel it. Air is made up of Oxygen, carbon dioxide and nitrogen. Plants take in carbon dioxide and with the help of sunlight, they are able to make the food they need to survive. Some bacteria in the soil can convert nitrogen into forms that plants can absorb and use to grow.
Air pollution occurs when toxic gases, dust or chemicals are released into the atmosphere from vehicles, factories, mines and other sources. Smog is a type of air pollution caused by oarticles and gases from burning fossil fuels in factories/industries.
Some gases and chemicals have been shown to affect the ozone layer. The ozone layer is a layer of ozone gas (similar to oxygen) found about 30 kilometers above the earth's surface. It protects the earth from dangerous energy from the sun. Some pollutants from air conditioners, aerosol cans have been shown to destroy the ozone layer. The destruction of the ozone layer results in dangerous radiations from the sun reaching the earth's surface and these may be associated with the occurrence of skin cancer.
Each planet in the solar system is drawn toward the sun by gravity. Gravity is a force of attraction between two objects. The strngth of the force depends on the mass of the two objects, and the distance between the two objects. The strength of the force decreases as the mass decreases and as the objects are positioned further apart.
The Earth is larger than the Moon so the expectation is that the strength of gravity will be higher on the Earth than on the Moon. In fact, the Moon's gravity is only about one sixth of the Earth's gravity.
Two objects do not have to touch each other to produce a force of gravity between them. The pull of gravity between Earth and the Sun acts across about 150 million kilometers of space. Gravity also acts across roughly 6 billion kilometers of space between the Sun and Pluto. However, because Pluto is located farther away from the Sun, the strength of gravity bwteen the Sun and Pluto is much lower than the gravity between the Sun and the Earth.
The force of gravity between the planets and between the planets and the Sun results in a path that the planets take around the Sun. These paths are called orbits.
As the Earth orbits around the Sun, it is pulled toward the Sun because of gravity but at the same time, inertia makes the planet move away from the Sun. Inertia is defined as the tendency of a moving object to continue moving in a straight line. The combination of gravity and inertia results in planets moving in a nearly cirvular orbit around the Sun called an ellipse.
When Earth is closest to the Sun, it is about 147,000,000 kilometers away. When Earth is furthest from the Sun, it is about 152,000,000 kilometers away.
The Earth moves aroudn the sun at a staggering 30km per second. The Earth's orbit is around 942,000,000 km long, so it takes the Earth about 365 1/4 days for the earth to make a complete trip around the Sun. This is called a Revolution and it is equal to one year.
An imaginary line drawn from the Earth's North to the South pole is called the Earth's axis. The Earth axis is tilted at an angle of about 23o. As the Earth revolves around the Sun, sunlight strikes different parts of the Earth at different angles. The changes in the angle result in seasons. When the Northern Hemisphere is tilted away from the Sun, the ground does not receive much heat energy and temperatures are low. In the Northern Hemisphere, this is the beginning of winter. At the same time, summer begins in the Southern Hemisphere. The Southern Hemisphere is tilted toward the Sun, the ground receives more heat energy and temperatures are warmer. In spring and in fall/autumn, both hemispheres receive equal warmth from sunlight, which makes temperatures mild.
The solar energy that reaches the Earth is called insolation. Insolation does not warm all places on the Earth equally. Because of the shape of the Earth, (sphere) and with an imaginary line (the equator) dividing the earth into two equal hemispheres, the sun strikes with the most vertical angle at or near the equator.
The atmosphere forms layers of gases around the earth. The layer of gsases cloest to the earth is called the trophosphere. This layer is thickest at the equator and thinnest at the poles. Above the trophosphere are the stratosphere, mesosphere, thermosphere, and exosphere.
Gases are more dense closer to the earth surface and become less dense as you move toward the exosphere. Tha gas particles press on the Earth's surface and on everything they surround. The force put on a given area by the weight of the air above it is called Air pressure or Atmospheric pressure. You do not feel this weight because atmospheric pressure pushes in all directions and these pushes balance each other.
The Moon has no atmosphere. Because there is no atmosphere, there are no winds and there is no weather on the Moon. There is no air to block radiation from the Sun or for astronauts to breathe. As a result, the temperatures on the moon can be as high as 123oC or as low as -233oC. Astronauts going to the moon need to wear spacesuits to protect them from the changes in temperature and from radiation. They also need containers of oxygen to breathe.
The cheese like craters on the moon are as a result of rocks traveling through space and hitting the Moon.
As the Moon revolves around Earth, different amounts of light reflect from the Moon’s surface and the Moon appears to change shape. A phase of the Moon is the appearance and shape of the Moon as you see it at a particular time. The phase depends on the location of the Moon in relation to Earth and the Sun.
An eclipse occurs when one object moves in front of another object in space.
A solar eclipse occurs when the Moon passes directly between the Sun and Earth. When this happens, the Moon casts a shadow on Earth. People on Earth see darkness move across the Sun.
A lunar eclipse occurs when the Moon moves into Earth’s shadow and is no longer reached by direct sunlight. This happens when Earth is between the Sun and the Moon.
If you are on Earth in the umbra during a solar eclipse, darkness covers the entire face of the Sun. This is called a total solar eclipse. If you are on Earth in the penumbra during a solar eclipse, darkness covers only part of the Sun. This is called a partial solar eclipse.
In lunar eclipses, Earth’s shadow causes the umbra and penumbra. Lunar eclipses may also be total or partial depending on whether or not the Moon is in the umbra or penumbra.
The pull of gravity between the Moon and Earth and between the Sun and Earth causes a bulge in the surface of Earth. On the part of Earth’s surface that is rocky, we do not notice this pull. However, the pull can be seen in the oceans and other large bodies of water. This pull causes the tide, or the rise and fall of the ocean’s surface.
When the Sun and the Moon line up and pull in the same direction. This causes higher high tides and lower low tides, called spring tides. The tides with the smallest range between high and low tides occur between these two spring tides. These more moderate tides are called neap tides. They take place when the Sun and the Moon pull in different directions and their pulls partly cancel each other.
Until 1610, when the telescope was developed by the Astronomer Galileo Galilei, people used to observe the sky using only their eyes. As you learnt in the previous topic that the air in the atmosphere has different densities. As light from stars travels through the air, the changes in density make the faint light of the stars appear fuzzy. Looking through a telescope makes dim objects seem brighter and also makes objects appear larger so more details can be observed.
The invention of the telescope played an important role in advancing our understanding of Earth's place in the cosmos. While there is evidence that the principles of telescopes were known in the late 16th century, the first telescopes were created in the Netherlands in 1608. Galileo Galilei (1564-1642) was part of a small group of astronomers who turned telescopes towards the heavens. After hearing about the "Danish perspective glass" in 1609, Galileo constructed his own telescope. He subsequently demonstrated the telescope in Venice.
Shortly after Galileo's first telescopic observations of the heavens, he began recording and drawing his observations. He wanted to get his findings out. His observations and interpretations of stars, the moon, Jupiter, the sun and the phases of the planet Venus, were critical in refining our understanding of the universe.
Above: Galileo Galilei's telescope
Above: The structure of the moon as observed and drawn by Galileo Galilei in 1610. The drawing already shows the topography of the moon showing the craters on the surface.
Telescopes can be placed in space to avoid the interference caused by variations in air density in the atmosphere. In 1990, the Hubble Space Telescope was placed into orbit around the Earth. This and other space telescopes gather more than visible light from objects in space, they can detect heat given off by stars and other space objects.
Radio telescopes are located on Earth and record data from radio waves given off by objects in space. Several dishes focus the waves so the radio waves data can be recorded and computers covert the data into images. Radio waves are not affected by air densities so they can move through the atmosphere without interference.
A solar system is made up of a star and the objects that orbit around it. In our solar system, there are eight planets orbiting the Sun. A planet is a large object that orbits a star. Form neares to the sun, the planets in our solar system include Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. The planets travel around the sun in elliptical or nearly circular orbits.
The inner planets are closer to the Sun than the asteroid belt and have surfaces made of rock. These planets are Mercury, Venus, Earth, and Mars. The outer planets are beyond the asteroid belt and have surfaces made of gases. These planets are Jupiter, Saturn, Uranus, and Neptune. Pluto was once known as the ninth planet. Pluto’s elongated orbit and small size were different from the other planets. Because of this, scientists debated whether Pluto should be classified as a planet. In Aug 2006, the International Astronomical Union officially reclassified Pluto as a dwarf planet. Other dwarf planets include Ceres and 2003 UB313, which is larger than Pluto but farther from the Sun.
Planet's unique features:
Jupiter: has the great red spot (aka red eye), which is a huge storm that has been blowing for over 400 years. It is believed that combination of sulfur and phosphorus are in Jupiter's atmosphere gives this storm its red color.
Saturn rings: First observed by Galileo in 1610. They are made of ice and rocks ranging in size from pea size to rocks larger than a house. Jupiter, Uranus and Neptune also have faint rings that are more difficult to observe.
Venus: The surface of Venus shows evidence of violent volcanic activity in the past. Venus has shield and composite volcanoes similar to those found on Earth. Long rivers of lava have also been observed on Venus.
Mars rocks! The dark boulders on the surface of Mars are volcanic rock fragments that have been found on Mars. These rocks look similar to rocks found near lava flows on Earth.
A moon is a natural object (natural satellite) that orbits a planet. Different planets have different numbers and sizes of moons. Generally, the outer planets have more moons. The Earth has only one moon while Jupiter has at least 63 moons. Saturn has 47 moons, Uranus has 27 and Neptune has 13.
An artificial satellite is an object that is put in space by man to orbit around the earth or other planets. These may be to monitor weather or conduct various forms of communication.
Moons vary in size. Ganymede is the largest moon in the solar system. In fact Ganymede is larger than Pluto and Mercury. The Earth's moon is also larger than Pluto and is clearly visible without a telescope.
When small objects in space collide with larger objects, a crater is formed. Craters are bowl-shaped holes on the larger object.
A comet is a mixture of frozen gases, ice, dust, and rock that moves in an elliptical orbit around the Sun.
An asteroid is a rock that revolves around the Sun. Most of the thousands of asteroids in the solar system are located between Mars and Jupiter in the asteroid belt.
An object that crosses paths with Earth and enters the atmosphere is called a meteor. Most meteors burn up before they reach the ground. When a meteor lands on the ground, it is called a meteorite.
Chelyabinsk meteor - 2013
A star is an object that produces its own heat and light energy. Stars go through stages from beginning to ending depending on how much hydrogen tha star contains. The star's cycle ends when it stops giving off energy.
All stars form out of a nebula. A nebula is a cloud of gases and dust. Gravity pulls the mass of nebula, which contains a lot of hydrogen atoms and as the atoms move closer they collide with each other producing heat. The temperature increases and when the temperature reaches 10 million degrees Celcius, the hydrogen atoms combine to form Ehlium. This process produces huge amounts of heat and light. This marks the beginning of the formation of a star.
The sun is a star, like other stars, it uses hydrogen as the source of energy. As the heat in the sun increases, it forces the hydrogen at the endge of the sun to expand into space, as the hydrogen moves further away from the center of the sun, it cools slightly and turns red. This stage of the star is called a red giant.
Eventually, all the helium is gone and the star begins to cool off and shrink becoming a white dwarf. A white dwarf is a small dense star that sines with a cooler white light. This is the end of the cycle for medium sized stars.
Stars that start with larger amounts of hydrogen (larger stars) end their cycle differently. After they become red giants the atoms at the core become so hot that they combine to form iron atoms. Eventually the iron gets so hot and explodes into a supernova. Supernovas shine brightly for days or weeks then they fade away.
If a star is very massive, it may end its life as a black hole. A black hole is an object that is so dense and has such powerful gravity that nothing can escape from it,not even light.
The sun is a medium sized star with a temperature of around 6000 degrees celcius. Giant stars are about 100 times larger than the sun and super giant stars are 1000 times larger. Neutron stars are the smalles stars.
Stars that form patterns are called constellations. Constellations were often named after animals, characters from stories, or familiar objects. Some constellations have been extensively useful to both ancient and modern travelers. For example, if you can see either the Big Dipper or the Little Dipper in the night sky, you can follow the line that their stars make to find Polaris, the North Star. If you travel in the direction of Polaris, you will be moving north. If you ever become lost in the woods or at sea, look for Polaris (North star) in the night sky. It will help guide you to safety.
The ancient Greeks divided the sky into 12 sections. They named some constellations after characters from Greek myths, such as Orion, a hunter, and Hercules, a hero.
Light Years
After the sun, the next closest star is called Proxima Centauri and is about 40,000,000,000,000 km away. This distance is so huge and becomes difficult to remember and comprehend. We can use the unit light year, which is equal to the distance that light travels in a year, and is equal to 9.5 billion kilometers. Proxima Centauri is 4.2 light years away from the earth.
Galaxies
A galaxy is a huge very distant collection of stars. Each galaxy holds billions of stars. The universe is full of galaxies and each galaxy differs in size and shape. Galaxies may be spiral, elliptical or irregular shaped.
Our solar system is part of the galaxy called the Milky Way. The stars you see in the sky are part of the Milky Way galaxy.
Clusters and Binary Stars
Some stars form clusters that may contain more than 100,000 stars. Clobular clusters are shaoed like a sphere. When two stars are close to each other, or somehow overlap and are seen as though they were only one star, they are called binary stars. the prefix -bi stands for 'two'. A star that seems to be blinking might actually be a binary star where one of the stars, the dimmer one, blocks the light from the brighter star.
The Big Bang Theory
The Big Bang Theory hypothesizes that the universe started with a big bang a single point and has been expanding ever since. Scientific evidence indicates that the big bang happened 13.7 billion years ago.
Energy is the ability to perform work, or to change an object. Work is the measurement of the energy used to peform a task. Work is a product of the force used to perform the task and the distance the force was applied. Therefor the units of measurement of work and energy are Newton.meters (N.m). If you lift a box that weighs 10 newtons onto a shelf that is 2 meters high, you are performing 20 N∙m of work (10*2). N.m are also known as joules (J). In describing how you lifted and moved the box, you could also say that you used 20 J of energy.
If you place a ball over your head but do not move (so that distance is zero) then you have not performed any work. Lifting the ball from the ground to the head is work, but keeoing the ball on the head for hors without moving is not work.
Forms of Energy
All forms of energy can perform work. When a spring is stretched, it has energy, but it is not moving. It has the potential to do work. Potential energy is the kind of energy that is stored in the position/location, or structure, of an object. An object on the surface of the table has potential energy due to its location/position on the table. When you release the stretched spring, it moves. Kinetic energy is the energy of a moving object. Potential energy could be Chemical energy due to the nature of the substance's atoms, or magnetic energy is also a form of potential energy. Electricity is a form of kinetic energy because it relies on the motion of eletrons. Sound is a form of kinetic energy due to the motion of particles as they move. Thermal energy is a form of kinetic energy due to the colision between particles in a substance.
We can detect several forms of energy using our senses. For example, we can detect heat energy, light energy (seeing), sound energy (hearing) etc.
Thermal Energy
Thermal energy is caused by the motion of particles in matter. Heat is the flow of thermal energy from one object to another due to the difference in their thermal energies. Thermal energy moves from an object of higher thermal energy to an object of lower thermal energy.
Temperature is a measurement of the average kinetic energy of particles in an object. objects with a higher temperature have particles that are moving faster, and vice versa. When two objects of different temperatures come into contact, thermal energy is transferred from the warmer object to the cooler object so the warmer object cools down while the cool object warms up to an equilibrium.
When two objects rub against each other, they become warm, because the kinetic energy changes into thermal energy.
Temperature is measured using a thermometer.
Please note that temperature and thermal energy are not the same thing. Thermal energy is the total amount of energy in a material due to the motion of the particles in that material. Temperature is a measure of the average kinetic energy of the material.
How does energy travel?
There are three main mechanisms in which thermal energy can be transferred from one object to another. These include:
Hot objects radiate energy. The electromagnetic rays they produce are called infrared rays. You cannot see these rays but you can feel them. The oven uses infrared rays to bake food. Some specialised cameras have been developed that can detect infrared rays and computers develop colors for the different levels of infrared rays, thereby creating a color coded image as shown here.
An infrared image of the hands. As you can see on the temperature scale, green colors indicate cooler temperatures while red colors indicate warmer areas.
The ability of a material to transfer thermal energy is called thermal conductivity. If a material conducts energy easily, it is described as a good thermal conductor. If a material conducts energy poorly, it is a good thermal insulator. Most metals are good thermal conductors, and most nonmetals are good thermal insulators. Thermal conductivity is usually highest in solids and lowest in gases. Solids are better conductors than liquids. Liquids are better conductors than gases. This is because, the closer particles are together, the more particles can bump into each other and transfer energy.
Heat Capacity
Heat capacity is a measure of how fast the temperature of a material will change. For example, 1 gram of oil will heat up faster than 1 gram of water. In this case, oil can be described to have low heat capacity. A materials heat capacity partly depends on the forces between its particles. Water molecules (particles) are tightly held together which gives water a high heat capacity.
Thermal energy as wasted energy
Although thermal energy is important in many situation, it is also produced as a by-product and wasted energy in many other situations. For example, a light bulb releases a lot of thermal, which is mostly unnecessary. Cars produce a lot of heat at the drive and this thermal energy is wasted. Your body muscles produce heat as they perform their chemical reactions. Thermal energy is the most common form of waste product from work.
An objects creates sound when it vibrates back and forth. The vibrations of a drum alternately squeeze air particles and then spread them out. This creates regions of air that have many particles, called compressions, and regions of air that have few particles, called rarefactions. The compressions and rarefactions move through the air, carrying sound energy. Each region of the air is only moved back and forth. Drums do not create a steady wind.
A series of many compressions and rarefactions traveling throudh a subtstance is called a sound wave. The substance through which the wave travels is called the medium for the wave. the sound energy is permanently moved from one part of the medium to another.
Sound waves vibrate the medium in the same direction that the energy moves. They are called longitudinal waves. They can also be represented as a series of peaks and dips. The peaks represent the high density of air in compressions. The dips indicate the low density of air in rarefactions. When sound waves hit an object, it can start vibrating. The object is moved by the energy of the wave. This is how sound from a loud car stereo rattles parts of the car or objects like pens inside the car.
Sound waves require a medium to travel through. Therefore sound can not travel in a vacuum. A vacuum is where there is few or no particles. Sound can travel in solids, liquids and gases. Sound tends to most quickly in solids and slowest in gases. The temperature of the medium also affects the speed of sound. In warmer air, particles move faster. As a result, they collide more often. With more collisions, the particles in warmer air transmit sound faster.
When a sound wave hits soft, thick, or uneven materials, the energy of the wave is absorbed. Absorption is the transfer of energy when a wave disappears into a surface. Absorbed sound waves become kinetic or thermal energy on that surface.
When sound waves hit a flat, firm surface much of their energy bounces back to form an echo. Echoes are sound waves that have reflected back at the speaker. Whenever a sound wave reflects off a surface, at least some of it is absorbed. Echoes are never as loud as the original sound wave.
Frequency describes the number of times an object vibrates per second. Its units are cycles per second (1/s) or hertz (Hz). High notes have a greater frequency than low notes.
Pitch is how high or low a sound is, and is related to frequency. In music, pitch is often given a letter name of “C,” “D,” “E,” “F,” “G,” “A,” or “B.” The series repeats itself so that the eighth note is “C” again. A series of eight notes is called an octave. Pitch and frequency are two different ways to describe sound waves. Pitch is the way our ears perceive frequency. It is closely related to the number of peaks in a sound wave, but is not the same thing as frequency.
You can increase the frequency of a sound wave by moving toward it. As indicated previously, Frequency is the number of peaks of a wave per second. If you move toward a wave, you will hear the peaks quicker than if you were standing still. A change in frequency due to moving away or toward a wave is called the Doppler effect.
Volume
The height of a sound wave is called its amplitude. The amplitude is how dense the air is in the compressions or rarefactions. The loudness of sound, i.e., volume, depends on the amplitude of the sound’s waves. You can make sounds louder by using more energy. For example, you can pluck a string harder, use more air in your voice, or hit a drum with more force. The extra energy increases the density of the particles in the compressions. Also, the rarefactions will be less dense than before. Changing the medium of a sound wave will also change its amplitude. The volume of a sound will be smaller the farther you travel from its origin.
Echolocation
Echolocation is when an animal or object can identify the location of another object by using the echo that is generated by the other object. Bats use echolocation to locate their food. Scientists have developed a system called sonar that works like echolocation does for animals. Sonar stands for “sound navigation and ranging.” It is used under water to find objects. The sonar system sends out sound waves that reflect off of objects. It then detects the reflected sound waves. The return time and direction of the sonar echoes are used to calculate the location of the object.
Below is an example of an echolocation call produced by Pipistrellus pipistrellus, an FM bat. A key feature of the recording is the increase in the repetition rate of the call as the bat nears its target – this is called the "terminal buzz",
Source Wikipedia under the Creative Commons Licence - Authored by Yannick Dauby.
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
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. They may be upright or upside down. They may also be enlarged or reduced. Convex mirrors always produce images that are upright and reduced.
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.
You have learnt that almost everything is matter. Matter is anything that has mass and occupies space (has volume).
An element is a material that cannot be broken down into anything simpler.
An atom is the smallest unit of an element that retains the properties of that element. You can look at atoms as building blocks in a lego set. Many lego pieces (atoms) are put together to make a model (element).
An atom consists of negatively (-) charged particles called electrons, positively (+) charged particles called protons and neutral particles called neutrons.
Electricity is the movement of electrons. Lightning, static electricity are both examples of electricity.
Static electricity occurs when two objects run against each other and eletrons are knowcked off one object onto the other. The build up of charged particles causes static electricity.
Opposite charges attract so protons are attracted to electrons and vice versa. Like charges will repel and spread out in the object. Static electricity causes electrons to jump through the air toward nearby protons causing a spark. An object that has equal numbers of protons and electrons is said to be neutral. Two oppositely chagred objects will cling together is a process called static cling. You will oberve this in a dryer or during winter if you wear a scarf or any light cloth.
When a charged object nears a neutral object, it pulls the opposite charge and pushes the other charge. The neutral object will act like it is charged. When charges form on a good conductor, such as a metal, the charge can move freely. When it forms on an electrical insulator, charges cannot move freely.
The Earth acts as an effective conductor. You can protect objects from static electricity by grounding them to the Earth with a wire. Grounding occurs when a conductor shares its excess chage with a larger conductor, in this case, the Earth, the charges that are passed onto the Earth are spread out and are barely noticed.
A flow of electricity through a conductor is called an electric current. This flow can be used to light up a bulb.
Batteries are necessary to increase the volts of electrons passing through the conductor. So batteries can be described as voltage sources.
An electric circuit is formed when an electric current passes through an unbroken path of conductors, which are often made of wires. A switch is a device that can open or close the path/circuit. When the switch is closed, the voltage pushes the electrons through the circuit.
An object in a circuit that resists the flow of electrons is called a resistor. Resistance is measured in units called ohms (Ω). Electrons lose enery when they pass through a resistor, this energy can be converetd into light or heat. A light bulb is an example of a resistor.
Electric current in a circuit travels fast - almost at the speed of light. Electrons, however, travel just a few millimeters per second. The amount of electric charge moving in a circuit is measured in units called amperes or amps (A).
Circuit diagrams are representations of circuits. If there is only one conductive path, its called series circuit. I this case, the resistance increases with each resistor added. Electricity flows through all the resistors one at a time so the energy that each subsequent resistor receives is decreased. A good example is a string of christmas lights wired in series where if one bulb doesnt work, the rest of the bulbs also stop working.
Circuits in houses and oter devices are parallel circuits. Parallel circtuits have more than one conductive path so the overall resistance of the circuit is lower, which causes more current to flow. Electricity flows in all paths of a parallel circuit at the same time, even if one path is broken the electricity can still flow in the other paths.
If a conductor accidentally forms a circuit it causes a short circuit. A short circuit is a path of little or no resistance that connects the ends of an electrical source. This causes large currents to flow across them and can damage appliances. Frayed wires, such as shown below, are a common cause of short circuits.
To protect against large currents, homes have fuses or breakers. A fuse is a wire that breaks if too much current flows through it. A breaker is a switch that opens when it detects too much current. Most homes have a breaker box with many breakers for different sets of circuits.
Delicate electronics, like computers, are often plugged into surge protectors. Surge protectors prevent sudden spikes in current from entering electronics and damaging them.
The electrical energy that comes to your home through power lines is dangerous. Never touch any electrical wires in the house. If you touch two power lines at the same time, or one power line and the ground, it can be deadly.
Magnetism is the ability of an object to push or pull another object that has magnetic property. Magnets also work with metals like iron and nickel.
A magnet has two poles, North (N) and South (S). Like poles repel, while unlike poles attract. Magnets always have a N and S pole, even if you break a magnet into two, it will form 2 magnets, each with a N pole and a S pole.
The Earth acts as a magnet with a North and South pole.
Atoms also act like magnets. In most non-magnetic materials, the N and S poles are random so they cancel each other. In materials where the N ans S poles of the atoms are aligned in the same direction, they form a permanent magnet. Iron, Nickel and Cobalt are attracted to magnets because their atoms can align to match those in the magnet thereby acting as weak magnets. When you place pieces of these metals over a magnet they form lines which correspond to the forces around a magnet called magnet field. The closer the lines are, the stronger the magnetic force in that area.
Electromagnets
An electromagnet is an electric circuit that produces a magnetic force. The moving electrons in the circuit generate a magnetic field.
The simplest electromagnet is a straight wire. the magnetic field circles around the wire when there is current flowing through the wire.
When you use the wire to make a loop, you increase the magnetic force. Many loops together result into a coil, which has a much stronger magnetic force.
If you place an iron rod in the coil, it becomes magnetized and makes the eletromagnet even stronger.
A generator is a device that generates an electric current by spinning an electric coil between the poles of a magnet. Energy is used to rotate the axle then as the coil moves through the magnetic field, the margentic forces push on its electrons and generate an electric current. Whenever the coil passes the pole of a magnet the direction of the current changes. This kind of current that regularly changes direction is called alternating current (ac). In US, generators produce alternating current that changes direction 120 times every second.
Magnetic levitation occurs when an object is lifted by means of a magnetic field. If you place the like poles of two magnets together, they will experience a pushing force. If the magnets were placed one on top of the other the one on top will appear as if its floating in the air.
Scientists have used this principle to design trains that use electromagnets on the track and on the train. Some of the electromagnets are arranged so that their poles are close together, this lifts the train slightly. Other magnets switch their poles back and forth and this creates an attraction force that propels the train forwards.
Contact Us