EVS_Food habits and Food chains.pdf

Food Habits and Food Chains SR 1 Let's Connect Back We have learned about the different habitats in the world. Such as polar regions, deserts, grasslands, ad oceans. Habitats are the natural homes of living beings that...

Food Habits and Food Chains SR 1 Let's Connect Back We have learned about the different habitats in the world. Such as polar regions, deserts, grasslands, ad oceans. Habitats are the natural homes of living beings that provide them with food, water, air, and Sneite for survival. Allliving beings need energy to live, to grow, and to perform variouS activities.They get this energy Trom e food they eat. How do living beings get their food? We know that plants can produce their own food tnroug the process of photosynthesis. However, for animals, depending on their type, their food may consist ot plants, animals, or a combination of both. Let us learn about the different types of animals based on the tood they eat. Herbivores: Herbivores are animals that feed only on plants. Their food includes leaves, grass, lowers, fruits, seeds, and roots. Some examples of herbivorous animals are deer, zebras, giraffes, rabbits, elephants,and Deer Zebra Giraffe Carnivores: Carnivores are animals that get theirfood by huntingand eatingthe flesh of other animals. Some examples of carnivorous animals are lions, tigers, crocodiles, foxes, wolves, eagles, cats, frogs, snakes, and Crocodile Lion Tiger Omnivores: Omnivores are animals that eat both plants and animals. Some examples of omnivorous animals are bears, pigs, hens, mice, human beings, and Pig Hen Bear Let's Think In this unit, we will use our knowledge of the different different feeding habits to learn more about how You already know about the food habits of all living beings on the earth are connected. to know more about how Iiving beings. Do you want We will also find out how this connection is based on their food habits? Iiving beings are connected Write any two questions you have on WS 1. useful for nature. Let us get started! LEAD 37  Chains SR 2 Food Habits and Food Scavengers and Decomposers are classified as herbivores (plant eaters), carnivores (meat eaters) and omnivoree We (plant meatanimals andthat know eaters), depending on their eating haabits. Now, look at the twoimages given below. Do you notice any similarity in the food habits of the vulture and the tiger? Yes, both the vulture and the tiger are feeding on the flesh of a dead animal. So, can both the animals be Considered carnivores? No. The tiger hunts and eats its food. Therefore, it is a carnivore. The vulture, on the other hand, only feeds on dead animals. Vulture Tiger Animals that feed on the remains of dead animals and plants available in their habitat are called scavengers. Some examples of scavengers are vultures, crows, hyenas, rats, ants, cockroaches, and jackals. Vulture Crow Hyena You must have seen leaves or twigs fallen on the ground. What do youthink happens to them after some time? Some small organisms will feed on the leaves and break them down into smaller forms in the soil. The organisms that feed on decaying waste materials in the soil and dead organisms are Keywords called decomposers. They help break down the waste materials into simpler decaying: rotting or forms or nutrients. These nutrients can then be used by plants to make food. spoiling Some examples of decomposers are worms, fungi (mushrooms), dung beetles, snails, and small organisms that are not visible to the naked eye. Such as bacteria. Earthworm Mushrooms Dungbeetle Scavengers and decomposers are Let's Think important organisms as they help maintain the balance in nature. Imagine a grassland habitat with different types of Iivng We will learn more about this in the beings. What do you think will happen if the scavengers and decomp0sers of that habitat disappear due to some reason coming sections. Write your answer on WS2. 38  SR 3 Food Habits and Food Chains Food Chain animals for We have so far learned that plants make their own fo0d and animals depend on plants or other food. Now, look at the image given below. Can you guess what it shows? Snake Grass Grasshopper Mouse grasshopper. Further, a snake In the given image, a grasshopper feeds on grass, and a mouse feeds on the the grasshopper, the mouse, feeds on the mouse. Thus, there is a feeding relationshio between the arass, habitat is called a food and the snake. The feeding relationship between different living beings in a particular chain. It shows us who eats whom. Producers and Consumers We know that all living beings need food for their survival. Depending on how they get their food inthe food chain, living beings are either producers or consumers. Green plants make or produce their own food Animals cannot make their own food. They in the presence of sunlight. Hence, they are depend on producers or other organisms for called producers. food. Hence, they are called consumers. consumers. Based on whom the animals depend on for food, there are three basic levels of Primary consumers: Consumers that depend on producers (green plants) for Scan me food are called primary consumers. They are usually herbivores. Some examples of primary consumers are rabbits, horses, grasshoppers, and giraffes. Secondary consumers: Consumers that eat primary consumers are called secondary consumers. Many secondary consumers also eat plants. Secondary consumers are Consumers are usually omnivores. Some examples of secondary dogs, cats, birds, mice, and bears. to watch a video called Tertiary consumers: Consumers that eat secondary consumers are tertiary on different levels of tertiary consumers. They are usually carnivores. Some examples of consumers. consumers are lions, polar bears, crocodiles, pythons, and dolphins. as it makes its own food. The Look at the food chain given below. Here, the grass is the producer for food. The mouse is the grasshopper is the primary consumer as it depends on the grass (producer) consumer) for food. The snake is the secondary consumer as it depends on the grasshopper (primary consumer). tertiary consumer as it feeds on the mouse (secondary Producer Primary consumer Secondary consumer Tertiary consumer Sun Grass Grasshopper Mouse Snake LEAD 39 SR 4 Food Habits and Food Chains Food Chains in Different Habitats We have already learned that habitats are the natural homes of plants and animals which provide them with the basic needs for survival. An with air, water, food, and a place ocean is an example of a habitat as it provides fish and other sea to live. creatures The four major habitats that we have studied are as follows: Oceans Deserts Polar regions Grasslands Every habitat has different animals that adapt to its unique weather Keywords conditions and availability of food. This gives rise to food chains that are unique to different habitats. Let us look at some of these food chains. unique:only one of a particular type Food Chain in Oceans in the food chain given below, the small fish feeds on the seaweed, and the large fish feeds on the small fish. Here, the seaweed is the producer, while the small fish and the large fish are the consumers. Seaweed Smallfish Large fish Food Chain in Deserts In the given food chain, the ground squirrel feeds on the cactus, and the desert fox feeds on the ground squirrel. Here, the cactus is the producer, while the ground squirrel and the desert fox are the Consumers. Cactus Ground squirrel Desert fox 40 EAD  Food Habits and Food Chains SR 5 Eood Chain in Polar Regions In the given food chain, the Arctic rabbit feeds on the plants inthe polar regions, and the Arctio wo wolf are feeds on therabbit. Here, the plants are the producers, while the Arctic rabbit and the Arctic the consumers. Arctic wolf Plants in the polar region Arctic rabbit Food Chain in Grasslands In the given food chain, the zebra feeds on the grass, and the lion feeds on the zebra. Here, the grass is the producer, while the zebra and the lion are the consumers. Zebra Lion Grass Let's Think Look at the food chains given below. Food Chain 1 Grass Grasshopper Mouse Snake Food Chain 2 Grass Grasshopper Frog Eagle Do yousee any connection between the two food chains? Write down your observations on WS 5. LEAD 41 SR 6 Food Habits and Food Chains Food Web We have learned that a food chain shows the feeding relationship between living habitat. Look at thefood chains 1 and 2 given on the previous page. In Food Chain 1,the beings in a particular food of the mouse. However, the grasshopper can also be the food of the frog that belongs to grasshopper Food is the Simlarly, the snake can feed on both the mousefrom Food Chain 1 and the frog from Food Chain 2. Chain 2. Thus animais Can be a part of more than one food chain, This creates an interconnection between different food chains. Anetwork of such interconnected food chains is called a food web. In tne fo0d web given below, a goat feeds on arass, This goat can then be eaten either by a wolf, or a lion. Slmilariy, a rabbit that feeds on grass can also be eaten by a wildcat or a wolf. Thus, multiple interconnected food chains. and an organism can be eaten by more in a to0dweb, there are than one organism. Lion Wolf Goat Eagle Wildcat Owl Rabbit Grass Snake Mouse A food web How many food chains can you find in the food web given above? Use a pencil and chains. circle the different food Food Chain and Food Web Do you know the difference between a food chain and a food web? Look at the image given food chain represents a single path of who eats whom in a particular habitat. A food web is aabove. A web of interconnected food chains from a particular habitat. In a food web, an organism can be eaten by multiple organisms, whereas in a food chain, an organism can be eaten by only one organism. In nature, we find many food webs in different habitats. Reflection Corner 1. Write down the most interesting thingyou learned about food chains and food webs. 2. Is there anything you found difficult regarding food chains and food webs? Write it below and show it to your teacher. 42  Food Habits and Food Chains SR 7 Nature's Cycle Nature works in sucn a way that whatever is taken from it is also returned to it Plants make their Own Too0 using energy from the Sun, water and nutrients from the soil, and carbon dioxide from the air. Plants are eaten by herbivores and omnivores. Herbivores are eaten by carnivores and omnivores. Dead plants and animals are eaten oy scavengers and broken down intosmall pieces.These small pieces are further broken down in the soll by decomp0sers. The soil thus becomes rich in nutrients and is used by plants. Tnis lomo acyclein nature, which maintains a balance. Producers Consumers Sun, air, and water Scavengers Primary Secondary Tertiary Scan me Water and soil Decomposers Let's Discuss You have already learned about decomposers earlier. Now, look at the image given above and try to answer the question given on SR 2 again. What would happen if the decomposers of a habitat disappeared due to some reason? to see nature's Share your thoughts with your partner. cycle. Why are decomposers important? Keywords Decomposers such as fungi and decomposing: breaking bacteria play an important role in Scavenger something into smaller pieces nature. They work at all levels of a food chain. Let us find out how. Tertiary Consumer 1. Decomposers feed on waste Secondary materials and decaying animals Consumer and plants in a habitat. Thus, they act as cleaning agents of Primary our environment. Consumer 2. They help in decomposing the dead bodies of plants and animals. 3. They draw nutrients from dead Organisms, which mixes with soil and water. These nutrients are used by plants to grow. Decomposer Producer LEAD 43 SR 8 Food Habits and Food Chains Energy Transfer in a Food Chain Scan me LIVing things get energy from the food theyeat. We have learned that a fod châin shows the feeding relationship between different organisms in a particular habitat. It also represents the flow of energy from one organism to another. Look at the Tood chain given below. As each organism in this chain feeds on the other, energy tlows through the food chain. The arrows show the flow ofenergy in the food chain. to watch a video on energy transfer in a food chain. Sun Grass Grasshopper Frog Snake Eagle Energy transfer in a food chain In the above example, the grass makes its own food using carbon dioxide, water, and energy from the Sun. When grasshopper feeds on the grass,this energy gets transferred from the grass to the grasshopper. From the grasshopper, itgets transferred to the frog. From the frog, it gets transferred to the snake, and then, to the eagle. Sun as the Source of All Energy Allconsumers directly or indirectly depend on producers, that is, plants, for food. This food is a source of energy for the consumers. Plants make their food through photosynthesis, in the presence of sunlight. Without sunlight, plants cannot make their own food. Thus, the Sun is the source of energy for all the food chains. The Sun is a vast source of energy. Unlike the energy from fuels, which pollutes the earth, the energy from the Sun is clean and does not cause any pollution. Hence, we should use this SOurce of energy instead of fuels to produce light and electricity. This would help reduce pollution and protect our environment. Let's Work Together Activity Corner On WS 9, draw a food chain using any four organisms Perform the activity on energy transfer in a from the list given below. Discuss with your partner food chain with a woollen/cotton ball, an A4 how energy transter takes place in the food chain. sheet of paper, sketch pens, and double frog, lion, snake, cow, eagle, grass, tiger, grasshopper sided tape. 44 XEAD  Food Habits and Food SR 9 Chains imbalance in Food Chains Natural disasters or the hunting of animals natural balance of by humans can upset afood chain. It is important to maintain the organisms in nature. If that of producers or primary consumers dropsthe bypopulation of tertiary alarge number, it causes consumers an imbalance or secondary food chain.or in theincreases Let us find out how. Consider the following food chain: Grass Zebra Lion Can you identify the primary and secondary consumers in this food chain? Here, the zebra is a primary consumer that feeds on the grass, whereas the lion is a secondary consumer that feeds on the zebra. If human beings destroy the grasslands onwhich zebras feed, they will have less food, and their population will go down. As a result, lions will have lessfood and they willgo out of the forests tolook for food. Similarly, if human beings hunt lions, there will not be enough lions to eat zebras, and the population of zebras willincrease. This will mean more zebras grazing on grasslands at a speed that is more than the speed at which grasslands grow. This will lead to a decrease in the availability of grass. Causes of Imbalance in Fod Chains Imbalance in food chains have many causes. Some of them are given below: 1. Loss of habitat 2. Predatory action Keywords 3. Diseases population: the number of living beings in a particular place Let us learn about each of these causes in detail. predatory: living by kiling and eating other animals Let's Think What are some causes of habitat loss that you already know about? Write your answer on WS 11. LEAD 45  Chains SR 10 Food Habits and Food Loss of Habitat (a) Natural disasters: Natural (b) Deforestation: Cutting trees (c) Pollution: Pollution of the disasters, such as forest and plants or clearing out soil, water, air, and land fires, tsunamis, and floods, grasslands has led to the has affected many habitats result in the loss of habitats destruction of animal habitats. and has led to an increase for many different types of This directly affects the in imbalance in food chains. plants and animals, leading Consumers in a food chain as For example, water to an imbalance. they are left with no food. pollution has badly affected the animals found in the 0cean habitat. Predatory Action (a) llegal hunting: Humans kill animals for (b) Human migration: The increasing human various reasons, such as selling animal body population has greatly affected animal habitats. parts for money or medicinal purposes and for For example, the dodo was a bird that lived recreation. For example, tigers are killed for undisturbed on the islands of Mauritius. recreation, and their skin and body parts are sold for use in certain traditional medicines. The Portuguese were the first humans to set foot in Mauritius. They killed a large number Elephants are killed for their tusks. Such of dodos for food. Also, the pigs and actions lead to an imbalance in food chains. monkeys introduced by humans destroyed dodo nests and further contributed to the of dodos. disappearance Keywords recreation: an activity done for enjoyment 46 LEAD  Food Habits and Food Chains SR 11 Disease Iiving beings are often affected by diseases that result in the death of organisms, causing an imbalance in food hains. For example, recent cases of lumpy skin disease in cows have greatly affected cows and other animalsthat are dependent on them for food. Effects of Imbalance in Food Chains Keywords An imbalance in a food chain may lead to the depletion of the population of a depletion: decrease certain species. Sometimes, the population of a particular species decreases so species: a group of muchthat it slowly disappears from the face of the earth. Species that no longer plants or animals that existon the earth are called extinct species. The passenger pigeon, the dodo, are all the same and the Tasmanian tiger are some examples of extinct species. Passenger pigeon Dodo Tasmanian tiger Species of animals or plants that are at risk of becoming extinct are termed endangered species. These species are in danger, and if not protected, they might become extinct. The chimpanzee, the blue whale, the Bengal tiger, and the Asian elephant are some examples of endangered species. Blue whale Chimpanzee Bengai tiger Ihus, we see that both natural factors and human actions are responsible for causing an imbalance in food wiins. Therefore. it is our responsibility to help maintain the balance in food chains. LEAD 47 SR 12 Food Habits and Food Chains Human Actions to Maintain Balance in Nature join hands and start working We have an important role to play in maintaining balance in nature. Let us towards it by following the steps given below. 1. Protecting forests and plants: We should plant trees in areas near our schools and houses. We should stop forests from being cut. This willhelp reduce the effects of deforestation. 2. Protecting and preserving endangered animals: Many species of animals are endangered and under threat of becoming extinct. We should work towards protecting these species by creating awareness amongst people. We should also avoid buying products made from the body parts of endangered species, such as belts and bags made from animal skin. 3. Reducing pollution: Various types of pollution are a major cause of destruction of habitats. We can take the following steps to reduce pollution: Throw waste only in a dustbin. Use paper bags instead of plastic bags,as plastic bags are not degradable. Also, do not throw plastic bags in waterbodies as they clog the waterbodies and pollute them. Reduce the use of fuels by using public transport. This will lead to less emission of harmful gases and, thus, reduce air pollution. Save energy by switching off lights and fans when not in use. Use solar energy for heating water and lighting lamps. This will help reduce pollution and protect our environment. Have youbeen folowing these steps to help maintain Keywords balance in nature? Use a pencil and put a tick mark degradable: capable of being against the steps that you have been following. decomposed. clog: block 48 EAD