Kids Learning Science

 

3rd Standard Science Term-III

Unit - 2

Animal Life

I. Animals in Different Environment

    Our Earth provides place for lakhs and lakhs of animals to live.  The living place of an animal or a plant is called habitat.  The basic needs such as food, water, shelter and place to breed are found in a habitat.

    Habitat can be as big as a forest or as small as a leaf.  Animals live in different conditions.  For example, whales live in sea (water) and foxes live in forest (land).

Land (Terrestrial) Habitat

    Animals that live on land are called terrestrial animals.  E.g., Ants, Cats and Lion. 

Some of the land habitats are :

1. Plains

2. Forests

Water (Aquatic) Habitat

    Animals that live in water are called aquatic animals.  E.g., Fish, Dolphin and Crab.

Water habitat is divided into two types :

1. Freshwater

2. Marine (Sea water)

II. Think and share.  Why should animals depend other living things for their food?

    Animals cannot make their own food.  They depend on plants or other plant-eating animals for their food.  They move in search of food.

III. Classification of animals based on their eating habits

Do all animals eat the same type of food?

    Have you ever seen a lion eating grass or a goat eating meat? What do not animals eat all types of food? It is because each and every animal have different food habits.

Herbivores

    Animals that eat only plants are called herbivorous animals or herbivores (Plant eaters).  E.g., Deer, Giraffe, Cow, Goat and Elephant.  They have sharp, straight edged, flat front teeth called incisors to bite the grass and leaves.

Carnivores

    Flesh eating animals are called carnivorous animals or carnivores.  E.g., Hyena, Tiger, Lion, Cheetah and Seal.  They have sharp, pointed teeth called canines.  Canines are used to tear the flesh of animals.

Omnivores

    Some animals eat both plants and the flesh of other animals.  These animals are called omnivorous animals or omnivores.  E.g., Bear, Man, Crow, Hen and Fox. These animals have a combination of tearing, biting and grinding teeth.

IV. Mouth parts of animals

(Conversation between teacher and students)

Teacher     :  Do you know the parts in your mouth?

Pandiyan   :  Lips, teeth, tongue.

Teacher     :  Good.  Do you know the use of teeth?

Vennila     :  They cut and chew the foodstuff.

Teacher     :  Fine.  Are all the teeth have same size and shape?

Vasu          :  No, Madam.

Teacher     :  Yes.  The teeth have different shape and size based on their functions.  Today, we will learn more about these mouth parts.  Mouth parts are different parts of the mouth that are adapted based on the nature of food that the animal eats.

Beaks of Birds 

Eagle

Eagle has strong, sharp, curved beak to catch prey and tear its flesh.

Kingfisher

Fish-eating birds hae spear-like beaks designed for stabbing fish.

Parrot

The hooked, sharp beak of parrot helps to collect and eat the grains.

Woodpecker

Strong chisel beak of woodpecker is used to make hole in the trees and catch small insects.

Sparrow

Sparrow has short, conical beak which helps to crack open the shells and extract the inner nut or seed.

Duck

Duck has flat beak that helps to grip plant and insect from water.

V. Food Chain

When you look around you can see the following.

The grass is food for deer and deer is food for tiger.

Plants food for ⁷⅞grasshoppers and grasshoppers are food for bird.  From these examples, we observe that plants are food for many animals, which in turn become food for other animals.

Let us look at the picture below :

      Grass             Deer           Tiger

    This is a food chain.  It gives us information on how living things are related with one another by the food they eat.  Here the grass is eaten by deer.  The deer is eaten by the tiger.

A food chain usually starts with  plants and ends with carnivores or omnivores.

Other examples for food chain

1. Leaves    -    Caterpillar        -    Hen        -    Hawk

2. Grass      -    Grasshopper      -    Rat        -    Owl

Food Web

      Every organism can feed on different kinds of food.  So a single organism will be a part of many food chains.  These food chains are interconnected to form a web.

    Hence, a Food web is an interconnection of multiple food chains.  Transfer of energy between organisms of different energy sources occurs through food web.

Air

I. Properties of Air

        Air is a natural resource.  We cannot live without it.  It is present around us.  It has no definite shape and colour.  Air has weight and it occupies space.  We cannot see air but it can be felt.  Air can flow everywhere.

Air occupies space

Materials required : A tumbler, a bowl and water.

Procedure :

        Place a tumbler on the surface of the water kept in a bowl (see picture).  Push the tumbler straight into the water.  Now, tilt it slightly and push it into the water.  Do you observe any difference? Yes air bubbles come out of water.

Hot air rises up

      Tie a ballon to the mouth of a bottle as shown in the picture.  Let the mouth of the bottle be narrow.  Keep the bottle in a vessel containing hot water.  Observe it for some time.  The balloon expands.  Why?

      Due to the heat of the water in the vessel, air inside the bottle becomes hot. Hot air fills the balloon.  Therefore the balloon expands. 

Air has weight

Procedure :

        Take two balloons.  Fill air in one balloon and keep the other balloon as it is.  Make a measuring tool using a stick and tie the balloons on both the ends as shown in the pictures.  Which balloon comes down and why? Do and find.

II. Air moves and pushes things

    Light an incense stick in the corner of the classroom and observe.  The smoke of the incense stick moves everywhere.  The air pushes the smoke.

     See the clouds in the sky that moves everywhere.  Clouds move because of the movement of air.

Electricity is generated from wind with the help of the windmills.

Let Us Do

        Can you remove a mall plastic ball from a glass vessel without physically touching it? Yes, you can.  If you blow towards one wall of the glass very hard and the ball will be ejected out of the glass.

Let Us Do

        Take a plastic bottle and fit a soggy newspaper pellet tightly in its mouth.  On pressing the bottle, the pellet will come out with a loud POP sound.

Air is required for burning

      Light a candle and place it on a table.  Now cover the lightning candle witha glass jar.  Observe what happens?

Air exerts pressure

    When you drink fresh juice, you suck it through straw.  We do this with the help of air.

How does a straw work?

      Mix a few drops of ink in half a glass of water.  Place a transparent straw inside the glass containing coloured water.  Then place your finger on the top of the straw and pull the straw out of the liquid.  What happens?

      Then remove your finger from the straw.  what happens?  While your finger covers top of the straw, the liquid remains in the straw.  When you remove the finger, the water flows out.

     When you keep your finger on the straw, you are lessening the pressure of air over the straw.  The greater pressure of air under the straw can hold the liquid inside the straw.

Let Us Do

Air Jack

Materials required : Empty plastic milk cover, a piece of thick string and an old pen body or pipe.

Procedure : Tie an old pen body or a pipe to the mouth of the milk cover with a string.  Place 3 or 4 thin note books up on the plastic milk cover and slowly blow air into it with your mouth.  As the cover gets inflated the books get raised.  How does that work? The pressure that you exert with your mouth is limited.  But the large area of the milk cover magnifies this pressure and lifts the books.

III.  Breathing (Inhalation and Exhalation)

Let Us Do and Discuss

Keep your finger near your nose and breathe.  Do you feel air on you fingers?

Try to count how many times you breathe in a minute.

Now jump 6-7 times.  It your breathing rate the same or is it faster?

Run 100 meters and stop.  Observe your breathing.

    All living things need air for their survival.  Plants breathe through leaves and fish breathe through gills.  Humans breathe in and breathe out through lungs.

    Inhalation is the process of taking the air inside and exhalation is the process of releasing the air outside.  The cyclical process of inhalation and exhalation is called breathing.

    We take oxygen and release carbon dioxide gas while breathing.

IV. Moving Air

Let Us Do : Take some sand in your hand and release the sand.  It falls in the direction of the wind.

    Moving air is called wind.  It moves across the surface of the Earth.  Based on the speed of air, wind cand be classified as breeze, storm and gale.

Breeze

    A gentle wind is called breeze.  Sea breeze and land breeze are the two types of breeze.

Sea breeze

    The breeze that blows from the sea towards of land during day time is known as sea breeze.  As the warm air from the land rises up and the cold air from the sea occupies the space over the land.

Land breeze

    The breeze that blows from the land towards the sea during night time is known as land breeze.  The warm air from the sea rises up, and the cold air from the land moves towards the sea.

Storm 

 Strong wind is called strom.  Sometimes storm can uproot trees and can destroy the crops.

Gale

    A very strong wind is call gale.  Gale is stronger than storm.  It damages trees and buildings a lot.