Caught in the web spider builds a web with lots of threads linked together. If one part of the spider’s web breaks, the whole structure is weakened. In a similar way, all the parts of nature join together to make an ecosystem. If we break one of the threads in the ‘web of nature’, the other parts of nature will also be weakened. These threads of nature that hold everything together are important to our survival. They are often invisible to us, but if you look hard enough, you might be able to see them! A The Earth is alive! Australian Aboriginals have traditionally believed that the whole Earth is living. They believe that animals and plants are not any different from the rocks, mountains, Sun, fire, water or air. After all, animals and plants cannot survive without these things. The Rainbow Serpent (carpet snake) is said to be the creator of life. She is responsible for the colours and shape of Earth. She called spirits to make the mountains, light, water and colour that brought Mother Earth to life. Do you think a mountain or river can be alive? The Sun is the source of all life on Earth. It supplies the energy that plants use to make their food. All animals depend on the food that plants make for their energy. Animals depend on rocks for shelter and a safe home away from those who may want to eat them. Lizards also sit on rocks in the Sun to get warm. Water is essential to all life. Animals and plants are mostly made up of water. Amazingly, your own body is made up of about 70 per cent water! Some animals and plants also live in water. Humans are animals too. Often we think we are not, but we depend on the ‘web of nature’ just like all other animals. 142 Science Alive for VELS Level 5 Go to worksheet 7.1: The web of nature Animals depend on trees and plants. Trees and plants provide food (fruit, flowers and seeds) and a home for many insects and animals. Plants also make some of the oxygen that we need to breathe. Many plants and animals have relationships that help each other. In this example, a bee is pollinating a flower so that the flower can make seeds. The seeds will grow into new plants. REMEMBER 1. What is an ecosystem? 2. What does biotic mean? 3. Give two examples of biotic factors in an ecosystem. 4. What does abiotic mean? 5. Give two examples of abiotic factors in an ecosystem. 6. Why is the Sun said to be the source of all life on Earth? THINK 7. Explain the term ‘web of nature’ in your own words. 8. How do insects that live on the tree in the picture depend on the water that is in the river? 9. How do humans interact with the other living and non-living things in the ecosystem shown? 10. Choose a human activity that may cause damage to the web of nature. Explain how the web may be weakened by this human activity. 11. Is the ecosystem shown at left connected to other ecosystems nearby? Explain. IMAGINE 12. Imagine that you are one of the animals, plants or abiotic features of the ecosystem shown. Write a story of a day in your life that describes your interactions with other species and the non-living things. For example, you may be the water that animals drink, part of you evaporates and rains down on other species, you soak into the soil and get drawn up by a tree, and so on. Many animals, like ants and worms, live in the soil. Worms also use the soil as their food. Plants can get nutrients from the soil through their roots. They also use the soil to support themselves. Living organisms interact with each other in an ecosystem. They also interact with the non-living parts of the environment they live in. The living things in an ecosystem are called biotic factors. They include animals, plants, food and predators. The non-living things in an ecosystem are called abiotic factors. These include water, rocks, soil, the Sun and weather. animals, plants and non-living things you depend on for survival. Record all of the ‘things’ that you use during the day. Some of them you will easily see — like the food that you eat. Others, like the air you breathe, may be harder to recognise. Set up a table to record your results. 143 7. Living together ✓ learning Animals depend on other animals for food. This is just another part of the web. INVESTIGATE 13. Keep a diary for a day to track how many living I CAN: explain the difference between biotic and abiotic factors in an ecosystem describe the relationships between living things in an ecosystem describe the relationships between living and non-living things in ecosystems. Who’s hungry? ll of the animals in a rock pool need to eat. Food is where animals get the energy they need to grow, move and reproduce. Some animals eat plants, but many eat other animals. What do you think the animals in this rock pool are having for dinner Other larger fish, such as the zebra tonight? A fish, may be found in rock pools. This fish feeds only on seaweed. Birds visit a rock pool to feed on fish, crabs, shrimp, sea urchins or shellfish. The octopus is an expert hunter. Octopuses eat fish, crabs or shrimp. Algae and sea plants use the Sun’s energy to make food. Algae and seaweed are producers. Sea stars eat anything they can find. This includes crabs, shellfish and algae. They push their stomach out through their mouth and digest food outside their body. The elephant snail has a shell that does not completely cover its body. It hides under ledges in rock pools and comes out at night to feed on algae. Many animals, such as this sponge, filter the water for plankton. Rock pool shrimp are scavengers. The blenny fish is a common rock pool fish that eats other small animals, recently dead meat or algae. Producers Many snails, such as the conniwink, chiton and limpet, eat algae. They use their rough tongues to scrape the algae off rocks. Sea urchins hide during the day and move about at night feeding on algae. They have spikes to stop other animals eating them. Producers are organisms that can make their own food. All plants make their own food using the energy of the Sun in a process called photosynthesis. In photosynthesis, plants use water, and carbon dioxide from the air, to make sugar (food) and oxygen. To do this, the plant also needs a green pigment called chlorophyll. This is usually found in the leaves. The food made by plants becomes food for animals. The chemical word equation for photosynthesis is: carbon dioxide + water sunlight sugar (food) + oxygen. chlorophyll Consumers Consumers are organisms that rely on other organisms for their food. Consumers feed on plants or other animals. The food is used as the material for growth and to release energy for living. The energy in foods is released in a process called respiration. Respiration takes place in every living cell. Plants also use respiration to release energy from the food they have made. Respiration is a chemical reaction in which organisms use oxygen and sugar to produce carbon dioxide and water. Energy is released during the reaction. The chemical word equation for respiration is: energy released oxygen + sugar Sea anemones have sticky tentacles that catch anything that floats by in the water. This includes fish, algae, microscopic animals, and plants called plankton. The dog whelk is a snail that eats other snails. It drills a hole through the snail’s shell with its rough tongue and sucks out the insides. carbon dioxide + water. Meat or vegetables? Carnivores are animals that eat only the meat of other animals. In a rock pool, these include the dog whelk and the octopus. Animals that eat only plants are called herbivores. The elephant snail and the green turban snail are examples of herbivores. Some animals have a more balanced diet and eat both animals and plants. These organisms are called omnivores. The sea star is an omnivore in the rock pool. The green turban is a snail that feeds on larger seaweeds. Crabs feed on dead or decaying material in rock pools. Animals that feed on dead and decaying material are called scavengers. They eat anything they can find. The decorator crab covers itself in seaweed for camouflage. 147 7. Living together Food chains Food webs A food chain shows how the energy stored in one organism is passed to another. Each organism depends on the one before. All food chains start with a producer, such as algae. The producer absorbs its energy from the Sun and provides the nutrients and energy that other animals need. Herbivores that eat the plants, such as the green turban snail, are called first-order consumers. Carnivores that eat first-order consumers, such as the dog whelk, are known as secondorder consumers. The seagull is a third-order consumer because it eats the second-order consumer. A food chain can be represented by a simple diagram. Many animals eat more than one type of food. This means that they are in more than one food chain. Joining a number of food chains together produces a food web. Note that some animals, such as the seagull, may actually be in more than one level, depending on which chain you follow to the top. A food web also has decomposers. Decomposers are organisms, such as bacteria, worms and fungi, that break down dead animals and plants. The nutrients in the dead animals and plants are recycled back into the food web. Energy Secondorder consumer: dog whelk Animal waste and dead organisms Third-order consumer: seagull Octopus Crab Zebra fish Green turban snail Shrimp Energy Blenny First-order consumer: green turban snail Energy Seaweed and algae Dead and decaying material Producer: seaweed Decomposers 148 Science Alive for VELS Level 5 An energy pyramid REMEMBER Producers absorb the Sun’s energy during photosynthesis to make sugar. Some of the Sun’s energy is stored with the sugar. When consumers eat producers, the energy is passed up the food chain. However, some of this energy appears to be lost at each link in the chain. But the energy cannot just disappear. Instead, it is transferred to the surrounding environment as heat, wastes, and even sound. This means that only a small amount of the Sun’s energy makes it to the top consumer. For energy to reach the animals at the top of the food chain, there must be many plants at the bottom of the chain. This means that a food web rarely has more than six trophic levels. At each level there are fewer animals of each type because there is less energy available. This is shown in the energy pyramid. Dog whelk Limpets 1. What are producers? 2. From where do producers get their energy? 3. What are consumers? 4. How do consumers release energy from the food they eat? 5. Write an equation for respiration. 6. What does a decomposer do? 7. What happens to the amount of energy available to organisms as it moves through an energy pyramid? THINK 8. What is the difference between a food chain and a food web? 9. Use examples to explain the difference between herbivores, carnivores and omnivores. 10. Give two examples, from the rock pool, of predators and prey. 11. What would happen to the animals in a rock pool if the seaweed and algae died? 12. What is the advantage of animals having more than one food source? SKILLBUILDER 13. Julie and James were studying animals in their local park. They made the following observations: • Grasshoppers eat grass. • Mice eat grass seeds and grasshoppers. • Small birds eat grasshoppers. • Snakes eat mice and small birds. • Kookaburras eat snakes. Energy Construct a food web using this information. The producers should be at the bottom. (a) Which organisms are producers? (b) Which are first-order consumers? (c) Which is a second-order consumer only? (d) Which is a second- and third-order consumer? (e) Which is a herbivore? (f) Which is an omnivore? (g) Which organisms compete for food? (h) Which have more than one food source? (i) What would happen if the snakes died out? Energy 1 Octopus Energy 2 Larger fish 6 Small fish 500 Plants This food chain has four trophic levels. 149 7. Living together ✓ learning Seagull I CAN: describe how plants and animals gain their energy describe how plants and animals depend on each other in a food chain explain how organisms depend on each other in a food web. Natural recyclers ross! Worms, maggots and bacteria! To most people these creatures are disgusting. But where would we be without them? These tiny organisms actually help to clean up the environment. They are the decomposers that recycle dead and decaying material. Decomposers can usually recycle anything that was once living. Material that can be broken down naturally is called biodegradable. Decomposers make the nutrients in dead things available for other plants and animals. Without them, the whole world would have dead animals lying around everywhere! G Flies and maggots Flies lay their eggs on dead and decaying animals. The eggs hatch into larvae that are called maggots. The maggots can quickly eat away large parts of a dead animal. The maggots grow up to become flies, which lay eggs somewhere else, or become food for other animals. This recycles the nutrients from the dead animal back into the ecosystem. Worms Worms are very effective recyclers. Worms eat just about anything and can do so quickly. They are especially good at recycling our food waste. Worms are found underneath dead organisms in the soil. They feed on animal and plant remains, recycling them into nutrients for plants. Fungi Bacteria Bacteria can grow on anything — dead or alive. They grow and reproduce very quickly. Bacteria reproduce by simply dividing in half. Bacteria feed on decaying material to help break it down and recycle nutrients for other animals. The photograph of the bacteria shown was taken under a microscope. Mushrooms and toadstools are fungi that feed on dead material. Another variety of fungi is called mould and looks ‘fuzzy’. Fungi grow microscopic threads into the food they are feeding on. These threads help to break down the dead organism. Fungi may become food for other animals, or they may decay. This allows the nutrients to be recycled back into the ecosystem. 150 Science Alive for VELS Level 5 Go to worksheet 7.3: Decomposers The amazing worm farm About 60 per cent of our household rubbish can be used as worm food. Worms will eat just about anything that was once living, including kitchen scraps, garden waste and manure. They love pizza and will even eat the box it comes in! Worms can eat about half their body weight in food each day. We can use a worm farm to feed our once-living rubbish to worms. This is how a worm farm works. The lid has ventilation holes to let air in. The holes are small so that flies and insects can not get in. The top level is still empty. There are holes between each level to allow the worms to move up when the level below is full. A bedding of shredded paper, manure, leaf compost, or a mixture of these, is added first. The bedding must always be kept damp. Food scraps are added on top of the bedding for the worms to eat. A sheet of newspaper or hessian is put over the top of the food to keep it dark. REMEMBER 1. What does biodegradable mean? 2. Name two types of biodegradable waste. 3. Name two types of nonbiodegradable waste. 4. What are the four types of animal that decompose dead things? 5. Why are decomposers also called natural recyclers? 6. Why are worms such good recyclers? THINK 7. Both bacteria and maggots are decomposers that feed on dead material. But they are also different types of organism. Compare the size and reproduction of bacteria and maggots. Liquid runs into the tray on the bottom and is known as ‘worm wee’. It makes an excellent liquid fertiliser for plants. 8. Explain why a worm farm is a useful way of disposing of some household rubbish. 9. Why are paper bags better for the environment than plastic bags? You could compare garden worms with some worms purchased at a garden centre. DESIGN AND CREATE 12. Build a worm farm for your class. This could be used to recycle your class’s lunch waste. Using an appropriate search engine, you should be able to find a simple design on the Internet. INVESTIGATE 10. Do some research to find out more about worms. This could include information about their body structure, how they reproduce, what they do or do not like to eat, and their behaviour. 11. Some types of worm are good recyclers and others are not. Design an experiment to test how good different worms are at recycling food scraps. 151 7. Living together ✓ learning Worms are placed in the bedding. The worms turn the bedding and food scraps into compost. This is the nutrient-rich ‘worm poo’. I CAN: describe how animals and plants are recycled explain the difference between biodegradable and non-biodegradable describe how a worm farm works. Life in the desert ife is rather tough in a desert environment. Desert plants and animals face extremes of temperature, food shortages and a lack of readily available water. To survive, they have to adapt to these harsh conditions. L Animal survivors Plants and animals of the Australian desert The bodies of desert creatures have adapted (evolved) to help them survive. Many are pale in colour, to reflect the heat. Some desert animals, such as reptiles, can vary their body temperature dramatically to cope with extremes of temperature. Some desert animals have very long legs to increase the distance between their bodies and the hot sand. Others have thick, leathery skins or hard, waxy shells to help them retain water, or thick fur or feathers to insulate their skin from extremes of temperature. Staying cool When it gets too hot, most desert birds look for shade. Some take off, to drift on the cool thermals that blow high above the hot sands. Many desert animals dig deep burrows in the ground, where they stay during the heat of the day, coming out to hunt at night. Desert storks and vultures urinate on their legs. The evaporating urine cools the skin, and the cooler blood then flows back into the body. Some creatures hop to minimise contact with the hot sand or, like lizards, they run extremely fast. Food and water supplies Most large desert animals survive because they are herbivores. They obtain moisture from the plants they eat. Others, like scorpions, get their moisture from their prey or from dew. The camel stores fat in its hump, and can go for days without drinking. The scarab beetle solves the problem of a scarce food and water supply by eating animal dung! Budgerigars feed on seeds produced by native plants. They are nomads, and in large flocks of a few thousand or more they follow the flowering cycles. Spinifex leaves roll into tight cylinders during the hot desert day to reduce the surface area exposed to the sun. Spinifex roots spread deep and wide to pick up both ground and surface water. Death adders are commonly found at night, soaking up the heat from roads. The spinifex hopping mouse does not sweat, its droppings are dry and its urine is very concentrated. A female feeds her young on concentrated milk and drinks their urine. 156 Science Alive for VELS Level 5 Honey ants store food and water in their abdomen, which swells up like a plastic bubble. When food is scarce, they vomit up the nectar to feed the colony. Go to worksheet 7.5: Create a desert animal Plant survivors Desert plants are made up of those that have adaptations for long-term desert survival, called perennials, and those that have a very short life cycle, called ephemerals. The seeds of desert ephemerals lie dormant for a long time, waiting for rain. After it rains, they grow rapidly, living their whole life cycle in a few days. Some desert perennials — for example, America’s mesquite tree The camel has a double row of eyelashes on each eye to keep out glare and grit. It stores energy as fat in its hump and can swallow about 100 litres of water at a time. or Australia’s river redgum — have very long root systems, often stretching down to the watertable. Others, such as succulents, have shallow but widely spread root systems so they can soak up and store lots of water when it rains. Many perennials have small leaves, often waxy, to reduce loss of moisture through transpiration. Some have no leaves at all — just thorns and spikes. REMEMBER 1. Why is survival a problem in a desert environment? 2. Describe the behaviours of two animals that help them survive in the desert. 3. Explain the difference between perennial and ephemeral plants. UNDERSTAND 4. Copy and complete the following table in your notebook. Mulga have specially shaped leaves and branches that funnel rainfall to the base of the tree. Plant or animal feature How it helps survival Small, waxy leaves Termites live in tall mounds of clay. They are protected inside the mound from the hot, dry desert winds. Large ears Pale colouring Hardy seeds Thick fur COMMUNICATE 5. Conduct some research to find out more about one of the following desert creatures or plants — particularly how it has adapted to its environment: fennec fox, pup fish, roadrunner, tarantula, Mitchell grass, Sturt’s desert pea, prickly pear. Create a colourful poster that includes photographs or drawings, a location map and interesting statistics. Rock wallabies rest in shady caves and crevices during the hottest part of the day. When no grasses are available, they can eat leaves, bark and roots. DESIGN AND CREATE 6. Design and label the perfect desert animal. Consider how your animal: • survives hot days and cold nights • obtains food and water • protects itself from predators. South Australia’s desert spadefoot toad hibernates in burrows for most of the year, coming out to breed and lay eggs only when it rains. The marsupial mole is blind because it has no need for eyesight when living underground. It moves underground by ‘swimming’ through the sand. 157 7. Living together ✓ learning Bilbies always stay close to one of several burrows they dig. These protect them from desert heat and predators. I CAN: see how animals and plants have adapted to a desert environment understand how a desert changes over time conduct research about animal adaptations.