01 Wonders of the Living World

T he environment is our surrounding including us. It consists of land,

water bodies, houses, plants, animals etc.

Let’s do the following activity to find out the components of the
environment.

Activity 1.1
yy Observe your classroom & the environment outside the class
room (school garden).
yy Then, list out what you could see in the environment.
You can observe many different things in the environment as well as in
the classroom. Different environments consist of different components.
Find out the things that you can see in the following environments.
(Fig. 1.1)

Fig. 1.1 Different environments

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Let’s identify the nature of the
components of the environment.
Can you wear a pair of shoes that
you used when you were a baby
? No, you can’t. Why is that ?

Now, the size of your body is

larger than earlier. The increase
in size, height or amount is
called growth.

Fig. 1.2
Can you see a growth in everything in the environment? Let's do the
following activity to find about it.

Activity 1.2
² Complete the following grid using the things you listed in
Activity 1.1.

Things that grow Things that do not grow

child pencil

It is clear that there is a growth in some components while there is no

growth in some components.
Components with a growth are called living things or living organisms.
The components without a growth are called non-living things.

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 Living things Non-living things

Fig. 1.3 Living and non - living things

Assignment 1.1

yy Observe your house and the garden. List out what you can see
and categorize them as living and non-living things.

Let’s do the following activity to study more about living things/

organisms.

Activity 1.3
yy Divide the living things listed in Activity 1.1 and Assignment 1.1
into two more categories.

It is easily understood that the two categories are plants and animals.
Therefore, it's clear that living things can be divided into two main
groups as plants and animals.

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Coconut Jak Bamboo Papaya
Fig. 1.4 Some plants

Fish Parrot

Deer Butterfly Snail

Fig. 1.5 Some animals
Are there any other organisms except plants and animals?

Activity 1.4
You will need -: some water taken from a pond, water rotted with
hay, a compound microscope, slides and cover slips
Method -: Put the water taken from a pond on to one slide and water
rotted with hay on to another slide. With the help of your teacher,
observe them under the compound microscope.

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When you observe the two water samples under the microscope, you
will be able to observe some tiny organisms. These organisms that
cannot be observed with the naked eye, are called micro-organisms.
Some micro-organisms that can be observed in the water taken from a
pond are shown in Fig 1.6.

Fig. 1.6 Some micro-organisms in a drop of water

The compound microscope is used to observe

things that cannot be seen with the naked eye.
A large number of micro organisms can be seen in water,
soil, air and in rotten food.

Fig. 1.7 Compound microscope

Assignment 1.2

Make a booklet including

yy information about micro - organisms,
yy uses of micro - organisms,
yy harms of micro - organisms.
Accordingly, organisms can be divided into three main groups. They
are plants, animals and micro-organisms.
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 Assignment 1.3

With the help of your teacher design an experiment to show that

there are micro organisms in soil.

1.1 Characteristics of Organisms

Growth

Fig. 1.9

Fig. 1.8
The above photographs show how the size of plants and animals is
increased with age. This increase in size, height or amount is called
growth. Growth is a common feature of organisms. There is no growth
in non-living things.
Let’s do the following activity to understand further about the growth
of organisms.
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 Activity 1.5
You will need (
few yoghurt cups with wet soil, some green gram seeds, a measuring
tape
Method (
yy Soak the seeds in water for one day.
yy Plant the seeds in the yoghurt cups with wet soil (make some
holes at the bottom of the yoghurt cups).
yy When the seeds are germinated and grown up to a certain height,
start measuring the height of the plants and observe the nature
of the leaves daily. (Get the help of your teacher)
yy Repeat it for two weeks.
yy Fill in the following grid with your observations.
Height of the green
Date Number of leaves
gram plants

You can observe the growth of the plants with time. (Fig 1.9)

Fig. 1.9 Germination and growth of a seed

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 Nutrition
All organisms including humans need food for survival. Satisfying the
food requirements of organisms is called nutrition.
Most green plants produce food within themselves. Hence, these plants
are called autotrophic.
They use carbon dioxide from air, soil water and sun light to produce
food. This process is called photosynthesis.

Sunlight

Oxygen

Carbon dioxide

Water

Fig. 1.10 Photosynthesis

Animals can’t produce their own food. They depend on plants directly
or indirectly. Therefore, animals are considered as heterotrophic.
Animals such as deer, cows etc. take plants as food. They depend on
plants, directly. But animals such as tiger, lion take flesh as food. So,
they depend on plants indirectly.
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 A cow eating grass A lion eating an animal
Fig. 1.11

For your extra knowledge

During the process of photosynthesis, plants absorb carbon

dioxide and release oxygen. So, the amount of these two gases in the
air can be kept constant.

Movement
Showing different movements is a common feature of living organisms.
Apart from movements, some animals can move from place to place.
Animals moving from one place to another place is called locomotion.
There are special appendages for animals for locomotion. Several
locomotions of animals are shown in fig 1.12 below.

Swimming Creeping Running

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 Flying
Fig. 1.12
Walking
There are some animals that cannot move, but they show different
movements. Sea Anemone, Coral Polip living in oceans are such
animals.(Fig 1.13)

Sea Anemone Coral Polip

Fig. 1.13
Assignment 1.4

Mention different types of appendages used by animals for

their locomotion and write names of animals as examples.
After a touch, the leaves of a touch me not (Mimosa) plant shows
a sleeping movement. Also, Albesia, Sesbenia (Kathurumurunga/
Agaththy), Tamarind leaves show sleeping movements in the evening.
These are some examples of movements of plants.

Fig. 1.14 Touch me not plant (Mimosa)

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Although, plants show many other movements, they cannot be observed
during a short period of time.
When a plant is kept on a window sill,
after some days the stem of the plant
bends towards the sunlight. This too is
a movement of a plant.

Fig. 1.15 Plant bending towards

sunlight

Non-living things do not move on their own. Non-living things will

move only when an external force is applied.
Respiration
When a person is lying in a relaxed position, you will see that his chest
and the stomach move up and down. Why?
It is because we take air in (inhale) and release air out (exhale). Oxygen
in the air, once breathed in, reacts with the food stored in the body
and produces energy. This process is called respiration. In the
process of respiration, oxygen is used and carbon dioxide is released.
Oxygen needed to breathe is taken in by inhaling while the produced
carbon dioxide is released by exhaling.
The chest moves up and down because of the process of inhaling and
exhaling. These movements are called respiratory movements.
Plants too breathe. But, they do not show respiratory movements as
animals.
Respiration is a common feature of every organism. There is no
respiration in non-living things.

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 Assignment 1.5
Observe and report the respiratory movements and respiratory
organs of different animals.

For your extra knowledge

The patients with respiratory difficulties are given oxygen artificially.

Also, mountain climbers and divers use artificial oxygen.
Let’s do the following experiment to find out whether exhaled air contains
carbon dioxide.
Activity 1.6
You will need ( a straw, a test
tube, colourless calcium hydroxide
solution
Method (
yyPut some colourless calcium
hydroxide solution into a test tube.
yyThen bubble the exhaled air
into the test tube as shown in
the Fig.1.16.
yyRecord your observations.
Fig. 1.16
You will see that the colourless calcium hydroxide changes into off
white. This happens due to the presence of carbon dioxide. Hence, the
exhaled air contains carbon dioxide.
Reproduction
It is obvious that every organism dies one day or the other. So, for the
continuation of the living world it is essential to have new generations.
A matured living being producing new members of the same species
is known as reproduction.

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 Fig. 1.17 Reproduction of some plants and animals
Fig 1.17 shows the reproduction of some plants and animals.
Reproduction of organisms occurs in different methods. Reproduction
is essential for the existence of living organisms. It's common for all
organisms. Reproduction does not occur in non-living things.

1.2 Differences between Animals and Plants

Diversity of Plants
yy There is a vast diversity among plants and animals in the environment.
yy Based on the nature of plants, they can be categorized as plants,
trees, shrubs and creepers.
yy Also there is diversity among plants in relation to morphological
features such as roots, stem, leaves, flowers, shape, size and colour
of fruits and seeds.
yy Plants grow not only on the terrestrial environments but also, on
aquatic, coastal and mangrove environments.

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 Based on morphological features
roots, stem, leaves, flowers, seeds,
fruits

Diversity among
plants

Based on living
Based on nature environment(habitat)
plants, shrubs, trees, creepers terrestrial, aquatic, mangrove,
coastal

Assignment 1.6

Observe the plants in the environment. Categorize them as plants,

shrubs, trees and creepers. Draw their flowers, leaves, seeds, fruits
etc. to identify the diversity of plants.

Diversity of Animals
The following figure shows that there is a vast diversity among animals
too.
Based on living
environment (habitat)
terrestrial, aquatic, air
Based on the feeding
Based on the mode of mechanism
locomotion chew & swallow,
walking, swimming, swallow without chewing,
flying, creeping
Diversity among chew, suck
animals

Based on external Based on the type of food

characteristics carnivores, omnivores,
colour, shape, herbivores
appendages

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You will learn more about the diversity among animals and plants in your
upper grades. Diversity among animals and plants is a very important
factor for the environment. It increases the beauty of the nature too. So,
it is our responsibility to care for and conserve the animals and plants.
You must not discharge harmful materials to the environment. Hence,
you too can take part in protecting the wonder of the nature.

Activity 1.7
yyStudy some plants and animals and identify the differences
between them.
yyFill in the following grid using the data you gathered.
Characteristics of plants Characteristics of animals

Compare the following table with the table you completed above.

Table 1.1
Characteristics of plants Characteristics of animals

Plants grow fixed to the ground.

They do not show locomotion, but Animals show locomotion.
show movements.
Do not produce their own food.
Produce their own food by
Depend on other plants and
photosynthesis. Hence, they are
animals for food. Hence, they are
autotrophic.
heterotrophic.

Chlorophyll is present within the Chlorophyll is absent within the

cells. cells.

Growth is visible during the Growth in animals visibly stops

entire life span. Thus, growth is after a certain period of time.
unlimited.

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Growth in animals visibly stops after a certain period of time.

Growth is visible during the entire life span.

Dichotomous Keys
It is very easy to use dichotomous keys to classify and identify organisms.
Categorization of organisms using the presence or absence of a
characteristic feature is known as a dichotomous key. It is more suitable
to use external features that can be easily observed.
Following figure shows how a dichotomous key is used to classify and
identify some leaves.

16 Science | Wonders of the living world

 leaves with leaflets leaves without leaflets

leaflets are divided leaflets are divided leaves with a leaves without a
at one place at different places pointed tip pointed tip

leaves with wavy leaves without

blades wavy blades

Following dichotomous key shows a classification of some animals.

Parrot, earthworm, dog, centipede, deer, crow

with four legs without four legs

^dog, deer& ^parrot, earthworm, centipede, crow&

with antlers without antlers with wings without wings

deer dog crow, parrot earthworm, centipede

with a curved beak without a curved with legs without legs

parrot beak-crow centipede earthworm

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 Assignment 1.7

Select 6 plants from the school garden and prepare a dichotomous

key to classify them. Show your dichotomous key to your teacher.

Summary
• There are living things (organisms) as well as non - living things in
our environment.
• Organisms can be classified into 3 major groups as plants, animals
and micro-organisms.
• Growth, nutrition, respiration, movements and reproduction are the
main characteristics of living organisms.
• There are many differences between plants and animals.
• There is a vast diversity among animals as well as among plants.
• Dichotomous key can be used to classify and identify plants and
animals.

Exercise
01. Select the most suitable answer.
^i&' A
characteristic that is not common to all living organisms.
a) respiration b) photosynthesis
c) growth d) reproduction
^ii&' The process that creates energy in organisms is
a) growth b) nutrition
c) reproduction d) respiration
^iii&' The chemical that can be used to identify carbon dioxide in
the laboratory is
a) copper sulphate b) calcium hydroxide
c) water d) coconut oil
18 Science | Wonders of the living world
(iv)' The gas emitted during the process of photosynthesis is
a) oxygen b) carbon dioxide
c) nitrogen d) hydrogen
(v)' The most suitable equipment to observe the micro-organisms in
water is
a) telescope b) compound microscope
c) magnifying glass d) binocular

02' Select the most suitable word and fill in the blank.
^i&' The energy needed for photosynthesis is supplied by
'''''''''''''''''''''''''''''' (sun / man).
(ii)' There '''''''''''''''''''''''''''''' (is / isn’t) a limit of growth within
plants.
^iii&' Most of the animals are ................................. (autotrophic/
heterotrophic).
^iv&' A characteristic which can be seen in animals but cannot be seen
in most plants is '''''''''''''''''''''''''''''' ^locomotion $ reproduction&'
^v&' An essential requirement for photosynthesis is ''''''''''''''''''''''''''''''
^oxygen $ carbon dioxide&'

03' Use a dichotomous key to classify the given plants.

grass, mango, guava, hibiscus, coconut

04' Use a dichotomous key to classify the given animals.

cat, butterfly, cock, cow, rat snake, leech

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 Project
Go on a field trip to study further about the characteristics and diversity
of organisms which you studied in the lesson "Wonders of the Living
World."Make a plan with your teacher to organize the trip.

Technical Terms

Organisms - Ôùka - E°µ[QPÒ

Non living things - wcSù øjH - E°µØÓøÁ
Environment - mßirh - `ÇÀ
Micro - organisms - CIqø cSùka - ~sn[QPÒ
Growth - j¾Okh - Áͺa]
Nutrition - fmdaIKh - ÷£õ\øn
Movement - p,kh - Aø\Ä
Locomotion - ixprKh - Ch¨ö£¯ºa]

Reproduction - m%ckkh - CÚ¨ö£¸UP®
Respiration - Yajikh - _Áõ\®
Photosynthesis - m%NdixYaf,aIKh - JÎzöuõS¨¦
Diversity - úúO;ajh - £ÀÁøPø©
Dischotomous key - fofnÿï iqÑ - CønUPÁºa_mi
Autotrophic - iajhxfmdaIS - uØ÷£õ\o
Heterotrophic - úIufmdaIS - ¤Ó÷£õ\o

20 Science | Wonders of the living world