NCERT Solutions for Class 9th Science
Chapter 7 – DIVERSITY IN LIVING ORGANISMS
(Complete Downloadable Chapter Solution PDF file is at the bottom of the page)
Q.1 Why do we classify organisms?
Ans Organisms are classified:
1) To make the study of wide variety of organisms easy and convenient.
2) Classification helps us in exploring the diversity of life forms.
3) Classification reveals the relationships among various groups of organisms and helps us in studying evolution.
4) Classification provides basis for developments in other branches of biology eg. crop improvement and animal breeding.
Q.2 Give three examples of the range of variations that you see in lifeforms around you.
Ans 1) Variations in size: On one hand we have microscopic bacteria of a few micrometre in size. While on the other hand we have blue whale and some big trees having size even around 100 m.
2) Variation in life: Some trees live for thousands of years while insects like mosquitoes die within a few days.
3) Variation in colour: Life also ranges from colourless or even transparent worms to brightly coloured birds and flowers.
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?
Q.4 What is the primary characteristic on which the first division of organisms is made?
Q.5 On what bases are plants and animals put into different categories?
Ans Plants and animals are put into different categories on the bases of:
1) Mode of Nutrition: Plants make their own food by the process of photosynthesis due to the presence of chloroplast whereas animals acquire food from others.
2) Locomotion: Plants are fixed whereas animals move in search of food, shelter etc.
3) Body Structure: On the basis of their needs, they have different body design. Plant cells have cell wall whereas animal cells do not.
Q.6 Which organisms are called primitive and how are they different from the so-called advanced organisms?
Q.7 Will advanced organisms be the same as complex organisms? Why?
Q.8 What is the criterion for classification of organisms as belonging to kingdom Monera or Protista?
Q.9 In which kingdom will you place an organism which is single celled, eukaryotic or photosynthetic?
Ans 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?
Q.11 Which division among plants has the simplest organisms?
Ans Thallophyta
Q.12 How are pteridophytes different from the phanerogams?
Q.13 How do gymnosperms and angiosperms differ from each other?
Q.14 How do poriferan animals differ from coelenterate animals?
Q.15 How do annelid animals differ from arthropods?
Q.16 What are the differences between amphibians and reptiles?
Q.17 What are the differences between animals belonging to the Aves group and those in the mammalia group?
EXERCISES
Q.1 What are the advantages of classifying organisms?
Ans Advantages of classifying organisms are:
1) It makes the study of wide variety of organisms easy and convenient.
2) Classification helps us in exploring the diversity of life forms.
3) It reveals the relationships among various groups of organisms and helps us in studying evolution.
4) It provides the basis for developments in other branches of biology eg. crop improvement and animal breeding.
Q.2 How would you choose between two characteristics to be used for developing a hierarchy in classification?
Ans For developing a hierarchy in classification, the characteristic which is more fundamental and basic out of the two must be chosen. These basic characteristics are independent of any other characteristics in their effects on the form and function of the organism. The characteristics in the next level would be dependent on the previous one and would decide the variety in the next level. This goes on to form a hierarchy of characteristics. For eg. plants differ from animals in many characteristics as the absence of locomotion, body design like presence of cell wall, chloroplast etc. But, only locomotion is considered as the basic or fundamental feature which distinguishes between plants and animals, because all these features are a result of locomotion. The absence of locomotion in plants gave rise to many structural changes such as the presence of a cell wall for protection, and the presence of chloroplast for photosynthesis (as they cannot move around in search of food like animals).
Q.3 Explain the basis for grouping organisms into five kingdoms.
Robert Whittaker classified all living organisms into five broad categories, called kingdoms. The five kingdoms are - Monera, Protista, Fungi, Plantae and Animalia. The basis for grouping organisms into five kingdoms is:
1) Cell Structure: On the basis of the presence or absence of membrane bound organelles, including a nucleus all living organisms are divided into two broad categories of eukaryotes and prokaryotes. Kingdom Monera includes all prokaryotes.
2) Cell type: On the basis of cellularity (cell type) eukaryotes are divided as unicellular or multicellular organisms. Unicellular eukaryotes form kingdom protista and multicellular eukaryotes form kingdom Fungi, Plantae and Animalia.
3) Body organisation: On the basis of presence or absence of cell wall, living organisms are further divided into two groups. Animalia does not have cell wall whereas Fungi and Plantae have cell wall.
4) Mode or source of nutrition: On the basis of mode of nutrition, Fungi and Plantae are further separated into two groups. Plantae prepare their own food and have autotrophic mode of nutrition whereas fungi does not make its own food and obtains its nutrition from assimilating organic matter i.e. has saphrophytic mode of nutrition.
Q.4 What are the major divisions in the Plantae? What is the basis for these divisions?
Q.5 How are the criteria for deciding divisions in plants different from the criteria for deciding the subgroups among animals?
Q.6 Explain how animals in Vertebrata are classified into further subgroups.