Our Environment

Class 6 | Science — Biology | Unit 4

Class 6 Unit 4 Science

Unit 4 Our Environment

Learning Objectives

• To acquire knowledge about ecosystems and their components
• To understand food chains and their role in ecosystems
• To learn about waste, their management and recycling
• To find out the difference between biodegradable and nonbiodegradable wastes
• To study different types of pollution and their impact on environment

Introduction

The surroundings or space in which a person, animal, or plant lives, is known as an environment. Environment is everything that surrounds us. It can have both living (biotic) and non-living things (abiotic). Abiotic factors are non-living things such as sunlight, air, water, and minerals in soil. Biotic factors are living things of our environment such as plants, animals, bacteria and more. Organisms live, constantly interact with one another, and adapt themselves to conditions of their environment.

4.1 The Ecosystem

Ecosystem is a community of living and non-living things that work together. Each part of an ecosystem has a role to play. Any changes in the environment such as increased temperature or heavy rains, can have a big impact on an ecosystem. Ecosystems can be either natural or artificial.

Activity 1. Think of the objects in your home

Just keep in mind the books, toys, furniture, food materials and even pets of your home. These living and non-living things together make your home. Look at the following picture and list out the living and non-living things, in the pond.

Natural ecosystem

Ecosystem originated without human intervention is called a natural ecosystem. This can be an aquatic ecosystem or a terrestrial ecosystem. The ecosystem in water is called the aquatic ecosystem. Sea, river, lake, pond and puddle are some examples of natural aquatic ecosystems. Ecosystems outside the water body and on land are called terrestrial ecosystems. Forests, Mountain regions, Desserts etc., are examples of natural terrestrial ecosystems.

Artificial ecosystem

Artificial ecosystems is created and maintained by human. They have some of the characteristics of natural ecosystems. They are much simpler than the natural ecosystems. These can be the terrestrial ecosystems such as paddy fields, gardens etc. or the aquatic ecosystem such as fish tanks.

Do You Know?

Aquarium

Aquarium is a place in which fish and other water creatures and plants are maintained. An aquarium can be a small tank, or a large building with one or more large tanks.

Terrarium

Terrarium is a place in which live terrestrial animals as well as plants are maintained. With controlled conditions that copy their natural environment. Aquariums and Terrariums are used to observe animals and plants more closely. They are also used for decorations.

4.2 Food Chain and Food Web

Living organisms need food to perform their physiological activities. Some organisms can produce their own food, such as plants, while other organisms cannot do this and depends on other organisms to obtain their food. We can therefore identify different feeding types of mechanisms in an ecosystem, based on how the organism obtain (that means - gets) their food. They are producers and consumers.

Producers

Producers are organisms that are able to produce their own food. They do not need to eat other organisms. Producers are also called autotrophs. Can you name an organism that prepares its own food? Plants are producers because they make their own food by photosynthesis. What do plants require for photosynthesis?

Consumers

Organisms which cannot produce their own food, have to eat other organisms as food. These organisms are called consumers. All animals are consumers as they cannot produce their own food. Consumers are also called heterotrophs. There are many types of consumers and we can classify them into specific groups depending on the food that they consume. These are

Herbivores

Animals which eat plants or plant products example: cow, deer, goat and rat.

Carnivores

Animals that eat other animals example: Lion, tiger, frog and owl.

Omnivores

Animals that eat both plants and animals example: Humans, dog and crow

Decomposers

Micro-organisms that obtain energy from the chemical breakdown of dead organisms (both plants and animals). They break complex organic substances into simple organic substances that go into the soil and are used by plants. Example: Bacterium, Fungi

Food chain

In a forest, deer eat grass, and in turn tigers eat deers. In any ecosystem there is a chain like relationship between the organisms that live there. The sequence of who eats whom in an ecosystem is called as food chain. It describes how an organism gets food and nutrients by eating other organisms. A food chain shows the relationship between producers example. grass, consumers example. deer, goat, cow and tiger and decomposer (example: Bacteria and Fungi)

Example: Food chain in a terrestrial (Grassland) ecosystem

Energy flow

The food chain begins with the energy given by the Sun. Sunlight triggers photosynthesis in plants. The energy from the Sun is stored in the plant parts. When the grasshopper eats the grass, the energy flows from grass to grasshopper. Frog gets energy by eating grasshoppers. This energy is transferred to a crow, when the frog is eaten by a crow. Thus we conclude the primary energy production in the world of living things is produced by plants, that is by photosynthesis. The microorganism degrade the excreta and the dead bodies of animals into primary simple components and puts them back into soil. It is this material that helps the plants to grow. Thus we can see that there is a cyclic movement of materials from primary producers to highest level predators, then back to the soil.

Trophic levels

The energy is passed from the producer to the consumers. But, there are three different consumers in any food chain. How can we distinguish different consumers? Animals that eat plants are primary consumers. Animals that eat primary consumers are called secondary consumers. Animals that eat the secondary consumers (mostly predators) are the tertiary consumers. There may even be large predators that eat tertiary consumers. They are called as quaternary consumers. Each of these levels in the food chain is called a trophic level. Organism uses up to 90% of its food energy for its life processes. Only about 10% of energy goes into new body cells and will be available to the next animal when it gets eaten. This loss of energy at each trophic level can be shown by an energy pyramid. A rat eats grains; and in turn we know snakes eat rats. Now snakes are prey for peacocks and in turn peacocks are easy prey for tigers and leopards. Now think? Do tigers have any natural predators? In all food chains there is a top level predator that has no natural predators. In an aquatic ecosystem there are no natural predators for alligators; in a forest there are no natural predators for tigers.

Importance of food chain

1. Learning food chains help us to understand the feeding relationship and interaction between organisms in any ecosystem.

2. Understanding the food chain also helps us to appreciate the energy flow and nutrient circulation in an ecosystem. This is important because pollution impacts the ecosystem. The food chain can be used to understand the movement of toxic substances and their impacts.

Food web

Consumers have different sources of food in an ecosystem and do not rely on only one species for their food. If we put all the food chains within an ecosystem together, then we end up with many interconnected food chains. This is called a food web. A food web is very useful to show different feeding relationships between different species within an ecosystem.

Activity 2. Create a Food Pyramid

Take a square paper. Fold its diagonals. Draw three lines in three triangles as shown in the picture. Cut from the edge of the diagonal to the centre as shown in the picture. If you fold this triangle and paste behind the third triangle you get a pyramidal shape. In one of the triangles, draw images of each of the organisms in the different levels. In another triangle write the names of the organisms. In the last triangle, write the energy level of the organism. Have a look at the following example. You must come up with different organisms.

4.3 Waste Management and Recycling

To protect our environment, it is very important to reduce waste, manage it properly and maximise recycling. Waste is any substance or material that has been used but is not wanted anymore. This is either because it is worn out, broken or no longer has any purpose. Everyone produces waste which has an impact on all ecosystems. However, most of us do not know where our garbage goes. There are many types of waste. There is liquid waste (in our drains), there are gases hiding in the air (like pollutants from factories) and there is solid waste (garbage) we put in our waste bins.

4.4 Biodegradable and Nonbiodegradable Waste

Solid waste we generate can be classified into two major types:

1. Biodegradable wastes

2. Non-biodegradable wastes

Activity 3. Waste Decomposition Experiment

Take two mud pots or glass jars and fill them up with garden soil. In the first pot, mix wastes such as banana peel, some vegetable peels and a few tree leaves into the soil. In the second pot, mix a piece of plastic carry bag, sweet wrapper and metal foil into the soil. What happen to the waste materials placed in both pots? Do you notice a difference between first and second pot? Observe the changes over two weeks and discuss with your classmates.

Biodegradable waste

The term 'Biodegradable' is used for those things that can be easily decomposed by natural agents like water, oxygen, ultraviolet rays of the sun and micro-organisms, etc. One can notice that when a dead leaf or a banana peel is thrown outside, it is acted upon by several microorganisms like bacteria, fungi or small insects in a time period. Biodegradable waste includes vegetable and fruit peels, leftover food and garden wastes ( that means - grass, leaves, weeds and twigs). Natural elements like oxygen, water, moisture, and heat facilitate the decomposition thereby breaking complex organic forms to simpler units. Decomposed matter eventually mixes for returns back to the soil and thus the soil is once again nourished with various nutrients and minerals.

Non-biodegradable waste

Those materials which cannot be broken down or decomposed into the soil by microorganisms and natural agents are labeled as non-biodegradable. These substances consist of plastic materials, metal scraps, aluminum cans and bottles, etc. These things are practically immune to the natural processes and thus cannot be fed upon or broken down even after thousands of years.

Give some examples for Biodegradable and Non-biodegradable waste.

Serial Number	Biodegradable waste	Non Biodegradable waste
1	Food waste	Plastic Bottles
2
3
4
5

Discuss with your teacher and friends.

1. Are animal bones biodegradable?

2. Are all types of clothes biodegradable?

Rani and her garbage

Rani gets home from school. She is hungry. She eats a banana and a packet of chips. She puts the banana peel and plastic chips packet into the waste bin. In the waste bin, the waste mixes together and the banana peels and makes the plastic chips packet dirty. The waste bin starts to smell and Rani's mother puts the waste outside on the street. The municipality collects the waste from outside Rani's house and many other houses in a tractor. The tractor drives to a big open dump and leaves all mixed wastes there. Sometimes, there are fires in the open dump. When waste like Rani's chips packet burns, unhealthy chemicals pollute the ecosystem. These chemicals are present in the air we breathe. The leftover ash from burning waste pollutes the soil. When it rains, some of the dangerous chemicals go into the ground. Some of the rain never reaches the ground as it collects in the plastic garbage at the dump. Little pools of water let mosquitoes to breed and they can spread unwanted diseases like dengue and malaria. Cows and dogs go into the open dump looking for food. As the waste is mixed, many things that are not good to eat such as plastics, smell like food. The animals get confused and eat some plastics by accident. This makes them sick. Rani is a student like you. She does not want to make animals sick. She does not want to pollute the beautiful Town. She does not like mosquitoes and wishes that no one ever gets sick from them. So, Rani takes this decision "I will dispose the waste property and reduce all types of pollution". Do you want to do the same as Rani does? Learn about the 3R's and how you can start to solve these problems.

4.5 Solid Waste Management

It is our duty to reduce creating waste and protect environment. 3R's are important in protecting the environment. The fist R is reduce and the second R is reuse and the last R is recycle. The waste hierarchy or pyramid shows the best ways to manage solid waste.

1. Avoid

Avoid the usage of unwanted materials which create more debris. Before you buy anything, think that "Do I really need it?" (example) Avoid buying packed foods. Refuse to buy use and throw plastic products.

2. Reduce

We can reduce the waste by using durable goods that last longer instead of things that are used once and thrown away. (example) Write on both sides of papers. Instead of unnecessary printing, use electronic facilities. Share newspapers, magazines, and other things with others.

3. Reuse

Reuse means using a thing again and again, rather than using and throwing after a single use. (example) Instead of using plastic bags, use and throw pens and batteries, use cloth bags, fountain pens and rechargeable batteries. Reuse glass bottles for other purposes. Repair foot wears and use them.

Do You Know?

creative reuse or up cycling is the process of converting waste materials or useless products into new materials or products of better quality or for better environmental value. When you up cycle, you are giving an item a new purpose example used tyres into chairs. used pet bottle into pen stand.

4. Recycle

The process by which waste materials are used to make new products is called recycling. (example) Using old clothes to make paper and melting some plastics to make floor mats, plastic boards and hose pipes.

5. Compost

The process of degradation of organic wastes into manure by the action of microorganism is called composting. The manure thus obtained becomes natural fertilizer for the plants as well as increases the soil fertility.

6. Incinerate

The burning of solid waste in an incinerator is called incineration. (discarded medicines, toxic drugs, blood, pus). During incineration, the enormous heat kills all contagious disease-causing germs.

7. Landfill

Landfilling is a method in which wastes are dumped into naturally occurring or man-made pits and covered with soil. Garbage buried inside landfills remain here for a long time as they decompose very slowly and become manure. These places can be converted into parks, gardens, etc.,

Earlier in the lesson, you learn about Rani and how she did not want to cause pollution. Simple steps in your daily life can make big differences. There are two steps you should remember.

1. The first step should always be to reduce waste. Think of the 3R's and the waste pyramid and remember the order of the levels.

2. The second step is to keep waste separate. This way the waste will remain clean and can be easily reused or recycled. Mixing different types of waste together (example) biodegradable and non-biodegradable) makes that place dirty.

Waste separation exercise

The Solid Waste Management (SWM) rules, 2016 say that,

Point number one: Every Household should segregate and store the waste generated by them in three separate streams – namely biodegradable, non-biodegradable and domestic hazardous waste in suitable bins and handover segregated wastes to authorised waste pickers or waste collector as per the direction or notification by the local authorities from time to time.

Point Number Two: Nobody shall throw, burn, or bury the solid waste on streets, open public spaces outside their premises or in the drain or water bodies.

Domestic hazardous waste means discarded paint drums, pesticide cans, CFL bulbs, tube lights, expired medicines, broken mercury thermometers, used batteries, used needles and syringes and contaminated gauge, etc., generated at the household level.

Learn how to separate waste correctly into 3 waste bins so you can keep Tamilnaduclean and beautiful!

Do You Know?

How much waste does each person make around the world every day? The average person in India produces 0.45 kg of waste every day. It may be small amount of waste. But, India has a large population and imagine you collected all the waste today and put it into tractors. You would fill so many tractors that you could create a traffic jam approximately 2,800 kilometres long. Imagine, a road all the way from Kanyakumari to New Delhi completely blocked with tractors carrying garbage and no space to walk in between. This is how much waste we create in India each day! If we reduce the waste, we reduce the pollution. Every day 532 million kilos of solid waste is generated in India.

Activity 4. Preparation of Vermicompost

Dig a pit for about one feet depth in the backyard or garden of your home or school. Fill the pit with bio wastes, paper and food wastes and place a few earthworms in it, sprinkle water and close the place with jute or cardboard and ensure moisture all the time. After 45 days the vermicompost casting layer formed just above the pit. These composts can be applied to the plant, which contains water soluble nutrients. This type of compost helps in plant growth as well as sustain the land is fertility.

4.5 Pollution

Pollution occurs when the environment gets contaminated by wastes, chemicals and harmful substances. Pollution is the damage caused to the environment mainly because of human activities. Any substance that causes pollution is known as a pollutant. Pollution is an unwanted change in the physical, chemical and biological characteristics of our land, air and water.

4.6 Types of Pollution

There are four major kinds of pollution

1. Air pollution

2. Water pollution

3. Land pollution that means soil

4. Noise pollution

4.6.1 Air

Most air pollution is caused by the burning of fossil fuels (example oil, petrol, coal and natural gas). They are used in industries, power plants and motor vehicles. Burning these fossil fuels release toxic gases and fine particles (such as ash and soot) into the air causing air pollution. Air pollution is also caused by burning solid wastes, like some plastics, gases or chemicals released from factories and fumes from aerosols (like deodorant spray cans) or paints. Certain toxic gases produced by industries mix with raindrops in the atmosphere and make rain unusually acidic. This is called acid rain. It damages plants, washes the nutrients out of soils and kills fish. Air pollution is harmful to all living organisms including humans. Polluted air affects skin, eyes and respiratory system.

How can we reduce air pollution?

Point Number One: Cycle or walk short distances instead of using a motor vehicle.

Point Number Two: Travel by public transport (bus or train)

Point Number Three: Do not burn solid waste.

Point Number Four: Avoid fireworks

4.6.2 Water pollution

Water pollution occurs when wastes from factories, houses, and farms mixes with the water in rivers, lakes, ponds, the ocean or even groundwater. Contaminated or polluted water can spread diseases and chemicals which are not good for our health. The most significant sources of water pollutants are

Point Number One: Sewage (water we use at home for bathing, cleaning, cooking).

Point Number Two: Industrial effluents (liquid wastes from factories).

Point Number Three: Agricultural pollutants (chemical pesticides and fertilisers that get washed from farms).

Point Number Four: Solid waste (when waste gets dumped into water bodies).

How can we reduce water pollution?

Point Number One: Do not pour leftover oil, old medicines, or waste down the drain or into the toilet.

Point Number Two: Reduce the use of chemical pesticides and fertilizers to grow crops.

Point Number Three: Use wastewater for the garden at home.

Point Number Four: Do not litter or dump waste – always use a waste bin.

4.6.3 Land (soil) pollution

In the same way as water and air get polluted, land or soil pollution happens when toxic chemicals change the natural balance in soil. Land pollution comes from farming (Excess use of chemical pesticides and fertilisers), mining (digging up metals and other materials), factories (industrial waste) and the solid waste from our own homes like plastics and broken electronics. Soil pollution affects animals, humans and even plants because soil or land acts like a sponge. When it rains, pollutants sink into the soil. If we grow plants to eat in polluted soils, these dangerous chemicals can get into our food.

How can we reduce land pollution?

Point Number One: First try to reduce waste, then recycle the rest.

Point Number Two: Always use a waste bin and never litter.

Point Number Three: Do not burn waste, the ash mixes easily with soil.

4.6.4 Noise pollution

Noise pollution affects the environment. We all like a quiet and peaceful place since unpleasant or loud sounds disturb us. Loud music, the sounds of motor vehicles, fireworks and machines cause noise pollution. Continuous noise disturbs our sleep and does not allow us to study. Noise pollution has been directly linked to stress and health impacts such as high blood pressure and hearing loss. Loud noise or even loud music can damage our ears. Noise pollution also disturbs animals. Birds have to communicate (talk) louder so that they can hear each other in noisy areas. Even underwater noise pollution from ships can make whales lose their way as they use sounds to navigate.

How do we reduce noise pollution?

Point Number One: Turn off your electronics when you do not use them.

Point Number Two: Lower the volume when you watch TV or listen to music.

Point Number Three: Remind drivers not to use the horn too much.

Point Number Four: Avoid fireworks.

Point Number Five: Speak, do not shout.

Exercise Classroom Exercise - Identify who am I?

Exercise number One: I am the type of pollution caused by burning of fossil fuels like petrol or coal and the smoke of burning garbage. I float around and cause breathing problems. I am pollution.

Exercise number Two: I am the type of pollution caused by loud sounds and I can cause serious damage to your ears and also affect sleep. In India, I am mainly caused by loudspeakers and honking of air horns of cars. I am pollution.

Exercise number Three: I flow from homes and farms into rivers and lakes. I kill fish and make water unfit for drinking. I am pollution.

Exercise number Four: I am the type of pollution caused by using too much chemical fertilizers and pesticides by farmers. I lower the quality of soil and even move chemicals into plant parts which are eaten by people. I am pollution.

Points to remember

• Living (biotic) and non-living (abiotic) components interact with one another.
• There are two types of ecosystems terrestrial (on land) and aquatic (in water).
• The feeding relationship in an ecosystem is called a food chain.
• Biodegradable and non-biodegradable waste should be kept separate
• The 3R's are in a certain order: First reduce, then reuse and finally recycle.
• Waste should never be burned as it causes air and soil pollution.
• Pollution occurs when the environment gets contaminated by wastes, chemicals and harmful substances.
• Major types of pollution are four: air pollution, water pollution, land pollution, and noise pollution.
• There are many small habits, any student can practice to reduce pollution, manage waste correctly and protect the environment.

ICT Corner

Our Environment

Through this activity you will be able to understand the atomic level of the process that plants use to convert solar energy into chemical energy.

Step 1: Type the URL given or scan the QR code to launch the activity. Food chain page will open.

Step 2: With the use of mouse drag the parts of the food chain - the animals or plants given to their correct place - in the empty boxes.

Step 3: When the chain is complete you can watch the food chain in action.

Step 4: Continue the activity by click on the next icon. Play and observe the various complex levels of food chain.

Our Environment URL: http://www.sheppardsoftware.com/content/animals/kidscorner/games/ foodchaingame.htm

Evaluation

Exercise 1. Choose the appropriate answer

1. Identify the freshwater ecosystem.

a. Pond b. Lake c. River d. All of them

2. Producers are

a. Animals b. Birds c. Plants d. Snakes

3. It is a biodegradable waste.

a. Plastic b. Coconut Shell c. Glass d. Aluminium

4. It is an undesirable change that occurs in air and water.

a. Recycling b. Reuse c. Pollution d. Reduce

5. Usage of chemical pesticides and fertilisers causes _____ pollution.

a. Air pollution b. Water pollution c. Noise pollution d. None of the above Exercise 2. Fill in the blanks

1. Primary consumers that eat plants are called

2. Temperature, light and wind are factors.

3. is the process of converting waste materials into new materials.

4. Water pollution can spread diseases in man.

5. The 3R's are Reduce, and Recycle.

Exercise 3. True or False. If False, give the correct statement 1. The Pacific Ocean is an example of a marine ecosystem. 2. Bacteria and fungi are called decomposers. 3. Human and animal wastes are examples of non-biodegradable waste. 4. Excessive use of pesticides leads to air pollution. 5. In schools, waste management rules say that we should separate waste in two categories. Exercise 4. Match the following

1. Biotic factor
2. Sewage
3. Fertilizers
4. Desert
5. Smoke

Options: Animals, Water Pollution, Land pollution, Terrestrial Ecosystem, Air pollution

Exercise 5. Arrange the following in a correct sequence and form a food chain

1. Rabbit - Carrot - Eagle – Snake

2. Human - Insect - Algae – Fish

Exercise 6. Give very short answer

1. Define ecosystem.

2. What are the two types of ecosystems?

3. Write any two things that can be recycled.

4. What are the types of pollution?

5. Give one example of a food chain in an aquatic ecosystem?

6. What are pollutants?

7. What are the pollutions caused by the objects given below?

a. Loud Speaker

b. Plastic

Exercise 7. Give short answer

1. What is biodegradable waste?

2. How can we reduce water pollution?

3. Write the importance of the food chain.

Exercise 8. Answer in detail

1. Give two examples of how you can avoid or reduce waste?

2. Write a short note on noise pollution.

Exercise 9. Question based on Higher Order Thinking Skills

1. What would happen if an organism is removed from the food chain?

2. Explain the link between waste and dangerous diseases like dengue and Malaria?

Exercise 10. See the diagram and answer the following questions

1. Explain what is happening in the picture?

2. What types of pollution are caused by open dumps?

📝 Summary

1. Environment consists of both living (biotic) factors like plants and animals, and non-living (abiotic) factors like sunlight, air, water, and soil minerals.
2. Ecosystems are communities of living and non-living things working together, which can be natural (like forests, lakes) or artificial (like gardens, aquariums) created by humans.
3. Natural ecosystems include aquatic ecosystems (sea, river, lake, pond) and terrestrial ecosystems (forests, mountains, deserts) that originated without human intervention.
4. Food chains consist of producers (autotrophs like plants that make their own food through photosynthesis) and consumers (heterotrophs like animals that eat other organisms).
5. Consumers are classified into different types including herbivores (animals that eat plants like cow, deer, goat) and carnivores (though the text cuts off before completing this definition).