NCERT Solutions Class 9 Science
The NCERT Solutions in English Language for Class 9 Science Chapter – 7 (Diversity in Living Organisms) has been provided here to help the students in solving the questions from this exercise.
Chapter – 7 (Diversity in Living Organisms)
Questions
1. Why do we classify organisms?
Answer – There are millions of organisms on this earth. So, it is harder to study them one by one. Therefore, we look for similarities among them and classify them into different classes to study these different classes as a whole. Classification makes our study easier.
2. Give three examples of the range of variations that you see in life forms around you.
Answer – Listed below are a few ranges of variations observed in life forms:
(a) Small frog to big whale
(b) Creeper to the eucalyptus tree
(c) Black cuckoo to colourful peacock
Questions
1. Which of the following 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 organisms is the kind of cells they are made of because different organisms may share same habitat but may have entirely different form and structure. So, the place where they live cannot be a basis of classification.
2. What is the primary characteristic on which the broad division of organisms is made?
Answer – The primary characteristic on which the first division of organisms is made is the nature of the cell – prokaryotic or eukaryotic cell.
3. On what basis are plants and animals put into different categories?
Answer – Plants and animals put into different categories on the basis of:
(i) Mode of nutrition: Plants can synthesise their own food, i.e., they are autotrophic while animals are heterotropic.
(ii) Movement: Plants are static, i.e., they can not move while animals can move.
(iii) Cell wall: Plants have cell wall made up of cellulose while animals do not have cell wall.
Questions
1. Which organisms are called primitive, and how are they different from the so-called advanced organisms?
Answer – Organisms with simple cellular stracture and no division of labour are called primitive. Advanced organisms, like mammals have millions of cells and there are system for different biological functions.
2. Will advanced organisms be the same as complex organisms? Why?
Answer – Yes, complex organisms are the same as advanced organisms. The consequence of advancement leads to multiple cell arrangements that operate uniquely.
Questions
1. What is the criterion for the classification of organisms as belonging to the kingdom Monera or Protista?
Answer – It is the presence or absence of a well defined nucleus. Monera has no nuclear membrane, while Protista shows well defined nucleus.
2. In which kingdom will you place an organism which is single-celled, eukaryotic and photosynthetic?
Answer – Kingdom Protista includes single celled, eukaryotic, and photosynthetic organisms.
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 organisms with a maximum of characteristics in common, whereas the kingdom will have the largest number of organisms.
Questions
1. Which division among plants has the simplest organisms?
Answer – Algae or Thallophyta has the simplest organism among plants.
2. How are pteridophytes different from phanerogams?
Answer – The following are the differences between pteridophytes and phanerogams:
| Pteridophytes | Phanerogams |
| They possess a naked embryo | They possess a covered embryo |
| Exhibit unclear reproductive organ | Exhibit well-defined reproductive organ |
3. How do gymnosperms and angiosperms differ from each other?
Answer –
|
Gymnosperm
|
Angiosperm
|
| They are non-flowering plants. | They are flowering plants. |
| Naked seeds not enclosed inside fruits are produced. | Seeds are enclosed inside fruits. |
| Pinus, Cedar, fir, Cycas, etc. are some examples of gymnosperms. | Coconut, palm, mango, etc. are some examples of angiosperms. |
Questions
1. How do poriferan animals differ from coelenterate animals?
Answer – Listed below are the differences between poriferan and coelenterate animals:
| Porifera | Coelenterata |
| Division of labour is not noticed | Division of labour is observed |
| The cellular level of the organisation exhibited | The tissue level of the organisation exhibited |
| Coelom absent | Coelom present |
2. How do annelid animals differ from arthropods?
Answer – Listed below are the differences between annelid and arthropods:
| Annelida | Arthropoda |
| The entire body is segmented into rings | Segmentation of the body into the head, abdomen and the thorax region |
| Skeleton is absent | Presence of exoskeleton |
| Hermaphrodites | Presence of different sexes, bisexuals present |
3. What are the differences between amphibians and reptiles?
Answer – Listed below are the differences between amphibians and reptiles:
| Amphibia | Reptilia |
| Skin is moist and soft | Skin is hardened |
| In water, they breathe through their skin | They can exist in water. They come to land to intake oxygen |
| Respire through lungs or gills | Respire through lungs |
| Capable of jumping | They crawl |
| Indirect development is noticed | Direct development observed |
4. What are the differences between animals belonging to the Aves group and those in the mammalian group?
Answer – Listed below are the differences between animals belonging to the Aves group and the mammalian group:
| Aves | Mammalia |
| Body is covered with feathers | Body is covered with hairs |
| Teeth absent | Teeth present |
| They possess a beak | Beak absent |
| Forelimbs are present and modified to take a flight | Forelimbs are present and used for multiple activities |
| Bones are hollow | Bones are solid |
| Body is streamlined | Streamlining of the body is not observed (except for whales) |
Exercises
1. What are the advantages of classifying organisms?
Answer – Following are the advantages of classifying organisms:
- It makes us aware of and gives us information regarding the diversity of plants and animals.
- It makes the study of different kinds of organisms much easier.
- It tells us about the inter-relationship among the various organisms.
- It helps us understanding the evolution of organisms.
- It helps in the development of other life sciences easy.
- It helps environmentalists to develop new methods of conservation of plants and animals.
2. How would you choose between two characteristics to be used for developing a hierarchy in classification?
Answer – Gross character will form the basis of start of the hierarchy and fine character will form the basis of further steps of single the hierarchy.
Example:
- Presence of vertebral column in human beings can be taken under vertebrat.
- Presence of four limbs makes them members of Tetrapoda.
- Presence of mammary glands keeps them under mammalia.
3. Explain the basis for grouping organisms into five kingdoms.
Answer – Basis of Classification:
1. Number of cells
2. Layer of cells
3. Presence or absence of cell wall
4. Mode of nutrition
5. Level of organization
4. What are the major divisions in the Plantae? What is the basis of these divisions?
Answer – The following table depicts plant division and the basis of classification for each division.
| Division | Basis of Classification |
| Thallophyta or Algae | Like body |
| Bryophyta | The body is divided into leaf and stem |
| Pteridophyta | The body is separated into root, stem and leaf |
| Gymnosperm | Seed-bearing, naked seeds |
| Angiosperm | Seed bearings covered seeds |
5. How are the criteria for deciding divisions in plants different from the criteria for deciding the subgroups among animals?
Answer – The characteristics used to classify plants is different from animals because the basic design are different, based on the need to make their own food (plants) or acquire food (animals).
Criteria for deciding divisions in plants are:
- Differentiated/ Undifferentiated plant body
- Presence/ absence of vascular tissues
- With/without seeds
- Naked seeds/ seeds inside fruits
6. Explain how animals in Vertebrata are classified into further subgroups.
Answer – The vertebrates are further classified into subgroups on the basis of server characters such as:
- The kind of exoskeleton or endoskeleton.
- Number of chambers in heart.
- The kind of respiratory organs.
- The method of reproduction and giving birth to young ones.
On the basis of above mentioned characters the vertebrate is divided into following classes.
- Pisces (fishes) – Exoskeleton of scales; two-chambered heart; breathing through gills.
- Amphibia – Three chambered heart; breathing through gills only in larva; skin slimy.
- Reptilia – Exoskeleton of scales or scutes; three chambered heart; laying eggs outside the water.
- Aves (birds) – Exoskeleton of feathers; four chambered heart; lays eggs.
- Mammalia – Exoskeleton of hair; four chambered heart; external ears; give birth to young ones.
