NCERT Grade 9-Diversity in Living Organisms-Answers – MySchoolPage

NCERT Grade 9-Diversity in Living Organisms-Answers

NCERT Solutions for Class 9 Science

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1.    Because of the huge biodiversity i.e. variety of life forms existing on earth it becomes very difficult to study them individually so scientists have made groups of organisms based on their similarities and dissimilarities. Such catergorisation of organisms is known as classification which help us to study them easily and systematically.

2.    We would choose the characteristic related to their structure and function that will help developing a hierarchy from one level to the next level. Like arthropods are organisms with jointed appendages but among arthropods insects and spiders make to separate groups having peculiar characteristics to define them. Hence we can make the hierarchy in classification by selecting general to specific characteristics.

3.    The basis for grouping organisms into five kingdoms is as follows:

(a) The organisms are made of prokaryotic or eukaryotic cells.

(b) The organism has a single cell in its body or is a multicellular life form.

(c) The organism prepares its own food or is dependent on other for food.

4.    Thallophyta: Plant body not differentiated into root, stem and leaf.

Bryophyta: Develop root like structures called rhizoids but lack vascular tissues.

Pteridophyta: Develop vascular tissue for conduction but lack seeds.

Gymnosperms: Develop naked sees and lack flowers.

Angiosperms: Develop seeds covered inside fruits and produce flowers.

5.    Animals are classified into subgroups on the basis of their level of body organization (cellular, tissue, organ grade) and symmetry, body cavity and presence or absence of notochord etc.

6.    Animals in Vertebrata are classified into further subgroups based on their development of nervous system, circulatory system, reproductive methods etc.

7.    A large number of organisms exist on this earth. We cannot study such enormous biodiversity one by one i.e. studying variety of life forms individually is an impossible task.

Hence, we make groups or categories of organisms depending upon their similarities and dissimilarities with other organisms. This allows an easier and systematic study of the life forms.

8.    (i) Life forms vary in their size – Some organisms are too small and cannot be seen with naked eyes like microorganisms while others are too big like the biggest animal which is the blue whale.

(ii) Number and type of cells – Some organisms have a prokaryotic cell like bacteria and that single cell performs all the required functions while others have eukaryotic cells organized into tissue, organ and even organ systems like human beings. iii) Mode of nutrition – Some organisms are autotrophic i.e. capable of making their own food eg plants while other organisms are heterotrophic i.e. they are dependent on other organisms for their food supply.

9.    The classification of organisms based on the place where they live is not quite convincing because other living in the same habitat they hardly share any other feature for example whales, corals, starfishes, octopus, fishes, sharks etc all are aquatic i.e. they live in water their appearance and all other features are very different.

Therefore classification of organisms based on the kind of cells they are made of is more widely accepted. For such catergorisation organisms belonging to prokaryotic group will have a particular cell structure and functional pattern which will be different from the eukaryotic group.

10.  The primary characteristic on which the first division of organisms is made is the form and functions of that organism.

11.  On the basis of their mode of nutrition plants and animals are put into different categories.

12.  Such organisms that possess quite simple structure and body design also haven’t changes much from their ancient sort of details even after long period of evolution on earth are called as the primitive organisms like bacteria who are still single celled and prokaryotic while advanced organisms have complex body design like trees and humans.

13.  Yes we can say that the advanced organisms are the same as complex organisms because advancement has occurred due to the process of evolution where a group of simple organisms have changed themselves into the complex form of life for better survival.

14.  The criterion used for classification of organisms as belonging to kingdom Monera or Protista is their cell structure.

Bothe Monerans as well as Protists are unicellular or single celled organisms but among monerans the cell is prokaryotic i.e. do not contain well defined nucleus while in protists the cell is eukaryotic i.e. have a well-defined nucleus.

15.  Kingdom Protista.

16.  Smallest number of organisms with a maximum of characteristics in common will be species while grouping with largest number of organisms with common characteristics will be the Kingdom.

17.  Division thallophyta.

18.  Pteridophytes do not produce seeds but develop naked embryos while phanerogams are seed producing plants like gymnosperms and angiosperms.

19.  Gymnosperms: They are plants producing male and female cones. They develop seeds but those seeds are naked i.e. fruits are not formed.

Angiosperms: They are flowering plants hence produce flowers as reproductive organs. They develop seeds those are covered inside fruits i.e. fruit information occurs.

20.  Poriferans:

(a) They bear pores on their body.

(b) They have cellular level body organization.

(c) Mesoglea absent.

Coelenterates:

(a) Pores are absent on body.

(b) They have tissue grade of body organisation.

(c) Mesoglea (body cavity) present.

21.  Annelids:

(a) Body cavity is true coelom.

(b) Body segmented and segments are called annuli.

(c) legs absent.

(d) Closed circulatory system.

Arthropods:

(a) Body cavity is haemocoel like in cockroach.

(b) Body segmented into head, mesothorax and metathorax.

(c) Three pairs of legs present.

(d) Open circulatory system.

22.  Amphibians:

(a) Body is soft and slimy without scales.

(b) Fertilisation external and lay eggs in water.

Reptiles:

(a) Body is covered with scales.

(b) Fertilization internal and lay eggs on land eg turtles.

23.  Aves:

(a) They lay eggs from which young ones hatch out.

(b) Body is covered with feathers.

(c) Bones are hollow or pneumatic.

Mammalia:

(a) They give birth to the young ones.

(b) Body is covered with hairs.

(c) Bones are filled with bone marrow.

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