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DIVERSITY IN LIVING ORGANISMS

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TEXTBOOK QUESTIONS AND THEIR ANSWERS

Q. 1. Why do we classify organisms?

Ans. There are more than a million kinds of living things exhibiting an infinite variety in form, structure and living places. It is not possible to know everything about all the organisms. We can study just a few representatives and get the idea about that group. Classification makes the study of such a wide variety of organisms easy. It is also important to understand the interrelationship among different groups of organisms. Classification serves as a basis for the development of other biological sciences as well.

Q. 2. Give three examples of the range of variations that you see in life-forms around you.

Ans. The range of variation in life forms is vast. Most common of these are size (living form ranges from microscopic bacteria to giant blue whale), colour (living beings range from colourless or even transparent worms to brightly coloured birds and flowers), and lifespan (like insects which live for



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only few days while pine trees live for thousand of years).

Q. 3. Which do you think is a more basic characteristic for classifying organisms?

(a) the place where they live

(b) the kind of cells they are made of. Why?

Ans. The kind of cells they are made should be the basic characteristic for classifying organisms. Classification should be based on fundamental characteristic and cell is the fundamental unit of all living forms.

An eukaryotic cell has membrane-bound organelles, including a nucleus, which allow cellular processes to be carried out efficiently in isolation from each other. Therefore, organisms which do not have a clearly demarcated nucleus and other organelles would need to have their biochemical pathways organised in very different ways. This would have an effect on every aspect of cell design. Further, nucleated cells would have the capacity to participate in making a multicellular organism because they can take up specialised function. Therefore, this is a basic characteristic of classification.

Q. 4. What is the primary characteristic on which the first division of organisms is made?



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Ans. The primary characteristics on which the first division of organisms is made, is whether the cells occur singly or they are grouped together. Cells that group together to form a single organism use the principle of division of labour. In such a body design, all cells would not be identical. Instead, groups of cells will carry out specialised functions. This makes a very basic distinction in the body designs of organisms.

Q. 5. On what bases are plants and animals put into different categories?

Ans. Plants and animals are put into different categories on the basis of whether they can produce their own food or not. Being able to produce one’s own food versus having to get food from outside would make very different body designs necessary. In this way, plants and animals have been categorised into different groups.

Q. 6. Which organisms are called primitive and how are they different from the so called advanced organisms?

Ans. Organisms which possess simple body organisation are called primitive organism.

They differ from so called advanced organisms as all the activities of life are performed by a single cell. i.e. they do not possess different organs or organ



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systems for performing various functions as found in advanced organisms.

Q. 7. Will advanced organisms be the same as complex organisms? Why?

Ans. Yes. As there is a possibility that complexity in design of an organism will increase over evolutionary time, it can be said that the younger organisms or advanced organisms are more complex in comparison to older one.

Q.8. What is the criterion for classification of organisms as belonging to kingdom Monera or Protista?

Ans. The organisms belonging to kingdom Monera are classified on the basis of following criteria :

These organisms do not have a defined nucleus and membrane bound cell organelles, nor do any of them show multicellular body designs.

Some of them have cell wall, some not.

Mode of nutrition may be autotrophic or heterotrophic.

The organisms belonging to kingdom Protista are classified on the basis of following criteria :



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These organisms are unicellular, eukaryotic organisms with well defined nucleus and membrane bound cell organelles.

Some of these organisms have hair like cilia or whip-like flagella for movement.

Mode of nutrition may be autotrophic or heterotrophic.

Q. 9. In which kingdom will you place an organism which is single celled, eukaryotic and photosynthetic?

Ans. The organism, which is single celled, eukaryotic and photosynthetic belongs to the kingdom Protista.

Q. 10. In the hierarchy of classification, which grouping will have the smallest number of organisms with a maximum of characteristics in common and which will have the largest number of organisms?

Ans. In the hierarchy of classification, the category “species” has the smallest number of organisms with a maximum of characteristics in common.

On the other side, the category “kingdom” has the largest number of organisms as it is at the top level of the hierarchy.

Q. 11. Which division among plants has the simplest organisms?

Ans. The plants belonging to the division thallophyta do not have well-differentiated body organisation.



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Q. 12. How are pteridophytes different from phanerogams?

Ans. Pteridophytes and phanerogams differ mainly in their reproductive organs.

The reproductive organs of pteridophytes are hidden

and poorly developed, and they are therefore called

cryptogams.

On the other hand, plants with well developed reproductive organs that ultimately make seeds are called phanerogams.

Q. 13. How do gymnosperms and angiosperms differ

from each other?

Ans.

Gymnosperms Angiosperms

(a) Seeds are not enclosed

within the fruit. So these

plants bear naked seeds.

(b) These plants lack flowers.

(a) Seeds are enclosed inside

the fruit formed.

(b) These plants bear flowers.

Q. 14 How do Poriferan animals differ from Coelenterate

animals?

Ans.Poriferan animals differ from Coelenterate animals in the

following ways :



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Poriferan animals Coelenterate animals

(a) These animals have many pores all over their body.

(b) They have cellular level of body organisation.

(c) Characteristic canal system is present.

(a) These animals have a

hollow cavity with a single

opening.

(b) They have tissue level of

body organisation with a

distinct division of labour.

(c) Gastrovascular cavity or

coelenteron is the main

feature.

Q. 15 How do annelid animals differ from arthropods?

Ans. Annelid animals differ from arthropods in the following

ways:

Annelids Arthoropods

(a) Body is soft, no hard

skeleton is present.

(b) Blood vascular system is of

closed type.

(c) Have setae for locomotion.

(a) Body is covered with hard

exoskeleton made up of

chitin.

(b)Blood vascular system is of

open-type.

(c) Have jointed legs for



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locomotion.

Q. 16 What are the differences between amphibians and

reptiles?

Ans. The difference between amphibians and reptiles are as

follows :

Amphibian Reptiles

(a) Amphibious in nature, i.e. found in water and on land both.

(b) Skin is having mucus gland but without scale.

(c) Respiration is through either gills or lungs.

(d) Lay eggs in water.

(a) First truly terrestrial

animals.

(b) Skin is with scales.

(c) Breathe through lungs.

(d) Lay eggs upon land.

Q. 17. What are the differences between animals belonging to

the Aves group and those in the mammalia group?

Ans. Differences between animals belonging to the Aves group

and those in the Mammalia group are as follows :

Aves Mammalia



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(a) Body is covered with feathers.

(b) Bones have air cavities.

(c) They are oviparous i.e. egg

laying.

(d) Forelimbs are modified for

flight

(a) Skin is covered with hair.

(b) Bones have no air cavities.

(c) They are viviparous i.e., give birth to young ones.

(d) Wings are absent.

Q. 18 How would you choose between two

characteristics to be used for developing a

hierachy in classification?

Ans. The characteristics to be used for developing a

hierarchy in classification may be the cell structure,

mode and source of nutrition and body organisation

of the organisms.

Q. 19 Explain the basis for grouping organisms into five

kingdoms.

Ans. The basis for grouping organisms into five kingdoms

are their cell structure, mode and source of nutrition

and body organisation.



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Q. 20. What are the major divisions in the plantae?

What is the basis for these division?

Ans. Major divisions in the plantae and the basis on which

they have been classified can be shown by the

following flow chart :

Bryophyta

Q. 21. What are the advantages of classifying

organisms?

Ans. Classification is the basic method which humans

employ to organise the living world. It has the

following advantages :



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1. Classification makes the study of the wide variety of

organisms existing in the living world convenient, easy

and time-saving.

2. Classification projects before us a picture of all life

forms at a glance.

3. Classification tells us about the inter-relationships

between different groups of organisms, and in turn

provides us information about their evolution.

4. It allows easy means of communication of information

to other people.

5. Classification is an information storage system and the

biologists need it for the specific organism they work

with.

6. Classification serves as a base for all other disciplines

of biology.

7. Various fields of applied biology such as agriculture,

environmental biology and public health depend on the

correct identification and classification of disease-

causing organisms and insect pests.



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Q. 22. How are the criteria for deciding divisions in

plants different from the criteria for deciding the

subgroups among animals?

Ans. The characteristics of body organisation used for

classification of plants will be very different from

those important for classifying animals. In case of

plants (i.e. make their own food), classification is

based on body is differentiated and has special

tissues for water transport etc. They bear seed or not,

the seeds are enclosed in fruits or not.

In case of animals, subgroups are formed on the

basis of how the body of the individual develops,

and organises in different parts, what are the

specialised organs found for different parts, what are

the specialised organs found for different functions,

etc.

Q. 23. Explain how animals in vertebrata are classified

into further subgroups.

Ans. Vertebrata is classified into five subgroups. These

are

1. Pisces 2. Amphibia



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3. Reptilia 4. Aves

5. Mammalia

Class Pisces

This class includes all fishes.

Characters

1. These are exclusively adapted to aquatic life.

2. The body is covered with scales.

3. Body is streamlined.

4. Fins are present but limbs are absent.

5. Respiration is through gills.

6. They are cold blooded and their heart have chest

two chambers.

Class Amphibia

The amphibians are the first land vertebrates, but

they are partly terrestrial and partly aquatic.



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Characters

1. These animals lack scales.

2. Mucus glands are present in skin.

3. Heart is three chambered .

4. Respiration is either through gills or lungs.

Class Reptilia

These are first truly terrestrial animals living in

warmer regions.

Characters

1. Cold-blooded animals.

2. Scales are present.

3. Heart is three chambered.

4. They lay egg upon land.

All birds fall in this category.

Characters



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1. Warm blooded animals. Body is covered with a

feathery exoskeleton.

2. Heart is four chambered.

3. Air cavities are present in bones.

Class Mammalia

Mammals are the most evolved group of organisms

and are found in diverse habitats ranging from

deserts, polar ice caps, oceans, mountains, forests

and grasslands.

They are named mammals as all of them possess

mammary glands (milk-producing glands).

Mammals are the only animals which feed their

young ones with milk.

Characters

1. Warm-blooded animals.

2. Skin is covered with hair. Hairs are provided with

sweat glands.

3. They are viviparous i.e., give birth to young ones.



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4. Heart is four chambered.

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