EXERCISES (Text book)
1. What are the advantages of classifying organisms.
Ans: Classification of organisms serves the following advantages:
(i) It determines the methods of organizing the diversity of life on Earth.
(ii) It helps in understanding millions of life forms in detail.
(iii) It also helps in predicting the line of evolution.
(iv) We can know all types of organisms at once.
2. How would you choose between two characteristics to be used for developing a hierarchy in classification.
Ans: We choose the characteristics which depend on the first characteristics and determine the next variety.
3. Explain the basis for grouping organisms into five kingdoms.
Ans: R.H. Whittaker proposed a five kingdom classification of living organisms. The basis are: Whether the organism is eukaryotic or prokaryotic, whether the organism is unicellular or multi cellular, whether the cell has a cell wall or not, whether the cell make their own food or not.
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4. What are the major divisions in the Plantae. What is the basis for these divisions.
Ans: 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.
5. How are the criteria for deciding divisions in plants different from the criteria for deciding the subgroups among animals.
Ans: Criteria for deciding divisions in plants are:
(i) Differentiated/ Undifferentiated plant body
(ii) Presence/ absence of vascular tissues
(iii) With/without seeds
(iv) Naked seeds/ seeds inside fruits.
Criteria for deciding subgroups among animals are:
Kingdom Animalia is divided into two major groups on the basis of the presence or absence of a notochord.
Non-chordates do not possess a notochord, while all members of the phylum chordates possess a notochord.
Non-chordate is further divided into subgroups on the basis of their features.
On the basis of their features, non-chordates are divided into the following subgroups: Porifera, Coelenterate, Platyhelminthes, Nematodes, Annelids, Molluscs, Arthropoda, and Echinodermata.
6. Explain how animals in Vertebrata are classified into further subgroups.
Ans: Animals in Vertebrata are classified into five classes:
(i) Class Pisces: This class includes fish such as 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 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.