Question 1. Why do we classify organisms?
Solution : 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.
Question 2. Give three examples of the range of variations that you see in life forms around you.
Solution :
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.
Question 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?
Solution : 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.
Question 4. What is the primary characteristic on which the first division of organisms is made?
Solution : The primary characteristic on which the first division of organisms is made is the form and functions of that organism.
Question 5. On what bases are plants and animals put into different categories?
Solution : On the basis of their mode of nutrition plants and animals are put into different categories.
Question 6. Which organisms are called primitive and how are they different from the so-called advanced organisms?
Solution : Such organisms that possess quite simple structure and body design also haven’t changed 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.
Question 7. Will advanced organisms be the same as complex organisms? Why?
Solution : 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 forms of life for better survival.
Question 8. What is the criterion for classification of organisms as belonging to kingdom Monera or Protista?
Solution : The criterion used for classification of organisms as belonging to kingdom Monera or Protista is their cell structure. Both 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.
Question 9. In which kingdom will you place an organism which is single celled, eukaryotic and photosynthetic?
Solution : Kingdom Protista.
Question 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?
Solution : 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.
Question 11. Which division among plants has the simplest organisms?
Solution : Division thallophyta.
Question 12. How are pteridophytes different from the phanerogams?
Solution : Pteridophytes do not produce seeds but develop naked embryos while phanerogams are seed producing plants like gymnosperms and angiosperms.
Question 13. How do gymnosperms and angiosperms differ from each other?
Solution :
| 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. |
Question 14. How do poriferan animals differ from coelenterate animals?
Solution :
| Porifera | Coelenterate |
| They are mostly marine, non-motile, and found attached to rocks. | They are exclusively marine animals that either live in colonies or have a solitary life-span. |
| They show cellular level of organisation. | They show tissue level of organisation. |
| Spongilla, Euplectella, etc. are poriferans. | Hydra, sea anemone, corals, etc. are coelenterates. |
Question 15. How do annelid animals differ from arthropods?
Solution :
| Annelids | Arthropods |
| The circulatory system of annelids is closed. | Arthropods have an open circulatory system. |
| The body is divided into several identical segments. | The body is divided into few specialized segments. |
Question 16. What are the differences between amphibians and reptiles?
Solution :
| Amphibian | Reptiles |
| They have a dual mode of life. | They are completely terrestrial. |
| Scales are absent. | Skin is covered with scales. |
| They lay eggs in water. | They lay eggs on land. |
| It includes frogs, toads, and salamanders. | It includes lizards, snakes, turtles, chameleons, etc. |
Question 17. What are the differences between animals belonging to the Aves group and those in the mammalia group?
Solution :
| Aves | Mammals |
| Most birds have feathers and they possess a beak. | They do not have feathers and the beak is also absent. |
| They lay eggs. Hence, they are oviparous. | Some of them lay eggs and some give birth to young ones. Hence, they are both oviparous and viviparous. |
Question 18. What are the advantages of classifying organisms?
Solution : 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 categorization of organisms is known as classification which help us to study them easily and systematically.
Question 19. How would you choose between two characteristics to be used for developing a hierarchy in classification?
Solution : 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.
Question 20. Explain the basis for grouping organisms into five kingdoms.
Solution : 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.
Question 21. What are the major divisions in the Plantae? What is the basis for these divisions?
Solution : The kingdom Plantae is divided into five main divisions: Thallophyta, Bryophyta, Pteridophyta, Gymnosperms, and Angiosperms.
The classification depends on the following criteria:
• Differentiated/ Undifferentiated plant body
• Presence /absence of vascular tissues
• With/without seeds
• Naked seeds/ seeds inside fruits
(i) The first level of classification depends on whether a plant body is well differentiated or not. A group of plants that do not have a well differentiated plant body are known as Thallophyta.
(ii) Plants that have well differentiated body parts are further divided on the basis of the presence or absence of vascular tissues. Plants without specialised vascular tissues are included in division Bryophyta, whereas plants with vascular tissues are known as Tracheophyta.
(iii) Tracheophyta is again sub-divided into division Pteridophyta, on the basis of the absence of seed formation.
(iv) The other group of plants having well developed reproductive organs that finally develop seeds are called Phanerogams. This group is further sub- divided on the basis of whether the seeds are naked or enclosed in fruits. This classifies them into gymnosperms and angiosperms. Gymnosperms are seed bearing, non-flowering plants, whereas angiosperms are flowering plants in which the seeds are enclosed inside the fruit.
Question 22. How are the criteria for deciding divisions in plants different from the criteria for deciding the subgroups among animals?
Solution : 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.
Question 23. Explain how animals in Vertebrata are classified into further subgroups.
Solution :
(i) Class Pisces: This class includes fish such as Scoliodon, tuna, rohu, shark, etc. These animals mostly live in water. Hence, they have special adaptive features such as a streamlined body, presence of a tail for movement, gills, etc. to live in water.
(ii) Class Amphibia: It includes frogs, toads, and salamanders. These animals have a dual mode of life. In the larval stage, the respiratory organs are gills, but in the adult stage, respiration occurs through the lungs or skin. They lay eggs in water.
(iii) Class Reptilia: It includes reptiles such as lizards, snakes, turtles, etc. They usually creep or crawl on land. The body of a reptile is covered with dry and cornified skin to prevent water loss. They lay eggs on land.
(iv) Class Aves: It includes all birds such as sparrow, pigeon, crow, etc. Most of them have feathers. Their forelimbs are modified into wings for flight, while hind limbs are modified for walking and clasping. They lay eggs.
(v) Class Mammalia: It includes a variety of animals which have milk producing glands to nourish their young ones. Some lay eggs and some give birth to young ones. Their skin has hair as well as sweat glands to regulate their body temperature.