Chapter 7 Diversity in Living Organisms

Class 9 Science Chapter 7 Diversity in Living Organisms NCERT Solutions

Page 80

1. Why do we classify organisms?

Answer:
There are millions of organism or species on earth. It is very difficult to study all of them one by one. The method of arranging organism into groups or sets on the basis of similarities and differences is called classification. 

2. Give three examples of the range of variations that you see in lifeforms around you.

Answer:
The range of variations that you see in lifeforms around us are:

1) A wide variety of plants, right from small grass to tall banyan tree.

2) Organism vary in size from microscopic bacteria to giant elephant, whale etc.

3) The colour of species is quite different. Some are colourless whereas some have beautiful colours.

Page 82

1. 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?

Answer:
The more basic characteristic for classifying organism is the kind of cells they are made of.This is because the type of cell forms the basis for classification.

2. What is the primary characteristic on which the broad division of organisms is made?

Answer:
The primary characteristic on which the broad division of organisms is made is nature of cell .Based on this we classify all organism as prokaryotic or eukaryotic.

3. On what basis are plants and animals put into different categories?

Answer:
Mode of nutrition and locomotion forms the basis on which plants and animals are put into different categories. They also differ in many other features such as cell wall is present in plant cells whereas absent in animal cells, chloroplast are present in plant cells whereas absent in animal cell and many other.

Page 83

1. Which organisms are called primitive and how are they different from the so-called
advanced organisms?

Answer:
Those organism which has simple body structure and ancient body features that have not changed much over a period of time are called primitive organism.

Those organism which have complex body structure and organisation with high level of division of labour, due to formation of organs and organ system are advanced organisms.

2. Will advanced organisms be the same as complex organisms? Why?

Answer:
It is not always true that an advanced organism will have a complex body  structure. Complexity in body evolves because of the necessity to adapt according to the changing environment. Therefore , at times advanced organism can be the same as complex organism.

Page 85

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

Answer:
The organism belonging to kingdom Monera are unicellular and prokaryotic whereas the organism belonging to Kingdom Protista are unicellular and eukaryotic.

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

Answer: Kingdom Protista

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

Answer:
In the hierarchy of classification, a species will have the smallest number of organism with a maximum of characteristics in common, whereas the kingdom will have the largest number of organism.

Page 88

1. Which division among plants has the simplest organisms?

Answer: Thallophyta

2. How are pteridophytes different from the phanerogams?

Answer:

pteridophytes	phanerogams
They have less differentiated reproductive organ.	They have well developed reproductive organs.
They produce naked embryos called spores.	They produce seeds.
For Ex: Ferns, marsilea.	For Ex : Pinus, cycas, fir

3. How do gymnosperms and angiosperms differ from each other?

Answer:

Angiosperms	Gymnosperms
These plants have covered seeds	They have naked seeds
They bear flower.	They do not bear flower.
Leaves are flat	Leaves are needle like
They are seasonal	They are evergreen .
Sepals and petals are present.	Sepals and petals are absent
Double fertilisation	Single fertilisation
For ex: Coconut, palm, mango etc.	For ex: pinus, cedar, fir

Page 94
1. How do poriferan animals differ from coelenterate animals?

Poriferan	Coelenterate
Their body is made up of single layer of cell.	Their body is made up of two layer of cells.
These are non-motile animals attached to some solid support.	Some species of this group live colonies while others have a solitary life span.
These are the organism with holes.	These are the organism having body cavity called coelenterate with a single opening.

 

3. How do annelid animals differ from arthropods?

Annelid	Arthropods
Body is segmented into rings.	Body is segmented into head, abdomen and thorax
They breathe through body surface.	They have different organs for breathing.
They contain true body cavity called coeloem.	The body cavity is present but it is blood filled and called haemocoel.
Legs are absent.	Three pairs of legs present.

3. What are the differences between amphibians and reptiles?

Amphibian	Reptiles
They have smooth, thin and permeable skin.	They have tough and scaly skin.
Fertilisation is external.	Fertilisation is internal.
They need water to lay eggs.	They do not need water to lay eggs.
Respiration is through lungs or gills	Respiration is through lungs.

4. What are the differences between animals belonging to the Aves group and those in the mammalia group?

Aves	Mammalia
Body is covered with feathers.	Body is covered with hairs.
Mammary glands are absent.	Mammary glands are present.
They lay eggs.	Mammals produce young ones.
Bones have air cavities.	Bones are solid, hard and filled with bone marrow.
Fore limbs are modified into wings.	Forelimbs are used for various activities.

Exercises Page 97

1. What are the advantages of classifying organisms?

Answer The method of arranging organism into groups or sets on the basis of similarities and differences is called classification. There are millions of organism or species on earth.It is very difficult to study all of them one by one.

Advantages of classifying organism are:

1) It makes the study of variety of organism easy.

2) It helps to understand the interrelation among different groups of organism.

3) It also help in predicting the line of evolution.

4)It helps in the development of other life sciences easy.

5)It makes us aware of and gives us information regarding the diversity of plants and animals.

2. How would you choose between two characteristics to be used for developing a hierarchy in classification?

Answer:
For developing a hierarchy of classification , we choose the fundamental characteristic among several other characteristic.By choosing the basic or fundamental characteristic, we can make broad division in living organism as the next level of characteristics is dependent on them.

3. Explain the basis for grouping organisms into five kingdoms.

Answer:
The basis for grouping organisms into five kingdom are:

1) Presence of cell wall: Presence or absence of cell wall leads into grouping.

2) On the basis of presence or absence of membrane bound organelles, all living organism are divided into two broad categories : Eukaryotes and prokaryotes.

3) Mode of nutrition: Organism show two modes of nutrition- autotrophic and heterotrophic.

4) On the basis of presence or absence of membrane bound organelles, all living organelles

4. What are the major divisions in the Plantae? What is the basis for these divisions?

Answer:
The kingdom plantae is divided into 5 main division:

Thallophytes
1)The plants body is not differentiated into stem,root and leave.
2)The plant in this group are called as algae.Most algae are aquatic but some are terrestrial ie live on land near moist places.
3)They are autotrophic.They contain green,red,brown,purple photosynthetic pigments.
4)They have cellulose cell wall around their cells.
5)For Example : Ulthroix, Chara, spirogyra, cladophara etc.

Bryophyta
1)They are small multicellular green land plants. They are called amphibians of plant kingdom.
2)The plant body is differentiated to form stem and leaf like structures.
3)There is no specialised tissue for conduction of water and other substance.
4)For Example : Riccia, Marchantia, Funaria, Barbula etc.

Pteridophyte
1)They are mainly found in shady or damp places.
2)the plants body is made up stem, root, leaves.
3)They have specialised tissue for the conduction of water and other substances.
4)Fertilised egg develop into embryo.
5)The plants have no flowers and do not produce seeds.
6)For Ex:Ferns, marsilea, azolla, pteris, horsetail, club mosses etc.

On the basis of whether seeds are naked or covered, there are 2 subdivision:
a)Gymnosperm
b)Angiosperm

Gymnosperm
1)They are simple seed plants.
2)The seeds produced by these plants are naked and not enclosed within fruit.
3)They are usually perennial(Plants that live for several years and has flowers every year),evergreen,woody.
4)For Ex:Pines, deodar, cycas etc.

Angiosperm

1)They are highly evolved plants and produce seeds that are enclosed within fruit.
2)The reproductive organs are present in flower.Since these plants have flowers,they are called flowering plants.
3)Plant embryo in seeds have structure called cotyledons. They are called seed leaves because they emerge and become green when seed germinate. They represent a bit of pre-designed plant in the seed.
They are of 2 types:
1)Dicotyledon(Dicot)
2)Monocotyledon(Monocot)

5. How are the criteria for deciding divisions in plants different from the criteria for deciding the subgroups among animals?

Answer:
Criteria for deciding division in plants are:
Differentiated/ undifferentiated body parts
Presence or absence of vascular tissue
Naked seeds or seeds inside fruit
With or without seeds

Animals are divided on the basis of their body structure. They can not be divided into groups on the basis of above criteria.

6. Explain how animals in Vertebrata are classified into further subgroups.

Answer:
They are grouped in to 5 classes:
a)Pisces
b)Amphibia
c)Reptilia
d)Aves
e)Mammalian

Pisces

1)They are water living animals.
2)Their skin is covered with scales or plates.
3)They obtain oxygen dissolved in water by using gills.
4)The body is streamlined.
5)Muscular tail is used for movement.
6)They are cold blooded and their heart have two chambers.
7)They lay eggs.
8)Certain fishes has skeletons made entirely of cartilage but some some has skeleton made of both bone and cartilage.
For Example : Lion , fish, torpedo, angler fish, dog fish, rohu, shark

Amphibia

1)These animals are found both in water and land.
2)Respiration is through gills or lungs.
3)They are 4 legged vertebrates.
4)They lay eggs.
5)Skin is smooth or rough, moist, slimy has mucus gland, without scales.
6)Three chambered heart.
For Example : Frogs, toads, Salamander, hyla

Reptilia

1)They are cold blooded terrestrial or aquatic vertebrates.
2)Body is covered with dry water proof skin.
3)Body is divided into head, tail, neck
4)Respiration is by lungs only.
5)Heart is three chambered whereas crocodile have four chambered heart.
6)Most reptiles lay eggs with tough covering and do not need to lay their eggs in water.
For Example : Snakes, turtle, lizards, crocodile, chameleon.

Aves

1)They are warm blooded and have four chambered heart.
2)They lay eggs.
3)There is an outside covering of feathers and 2 forelimbs are modified for flight.
4)They breathe through lungs.
5)Smallest bird is humming bird and largest is Ostrich.
6)Boat shaped body is divided into head, neck, tail.
7)Forelimbs modified into wings for flight.
8)Hind limbs bear four clawed digits and adapted for walking, perching.
9)There is horny beak.
10)Bones are light and spongy due to the presence of air cavities.
11)4 chambered heart.
For Example : Ostrich, sparrow, crow, pigeon, parrot, vulture, duck etc.

Mammalian

1)They are warm blooded with 4 chambered heart.
2)They are mammary glands for the production of milk to nourish their young ones.
3)Their skin have hairs, sweat and oil glands.
4)Teeth are embedded in socket in the jaws and differentiated into incisors, canines, premolar, molar.
5)2 pairs of pentadactyl limbs are present.
6)A muscular diaphragm separates thoracic and abdominal cavity.
7)Respiration is by lungs only.
8)4 chambered heart.
9)They are viviparous
For Example : Kangaroo, fox, rat, squirrel, cat, lion, dog, tiger etc.