11 Biology

Living World

NCERT Solution

Question 1: Why are living organisms classified?

Answer: There is a huge diversity among living beings. The huge diversity presents a challenge to systematic study of living beings. Classification is required to facilitate systematic study of living beings.

Question 2: Why are the classification systems changing every now and then?

Answer: No theory of system in science is cast in stone. Formation of new concepts is an ever evolving process in any science. Classification system too is continuously evolving. A discovery of a new trait or a new species may make it necessary to alter the existing system of classification. Due to this, the classification system is changing every now and then.

Question 3: What different criteria would you choose to classify people that you meet often?

Answer: We can classify people on the basis of their education, profession, hobbies, native place, gender, etc.

Question 4: What do we learn from identification of individuals and populations?

Answer: Through identification of individuals and populations; we can learn about the native place, mother tongue, costumes, food habit, religion, caste, etc.

Question 5: Given below is the scientific name of Mango. Identify the correctly written name.
Mangifera Indica, Mangifera indica

Answer: Mangifera indica

Question 6: Define a taxon. Give some examples of taxa at different hierarchical levels.

Answer: A particular level of hierarchy in the classification of living beings is called a taxon. Following is the representation of taxa at different levels:

different levels of biological classification

Question 7: Can you specify the correct sequence of taxonomic categories?

  • Species , Order, Phylum, Kingdom
  • Genus, Species, Order, Kingdom
  • Species, Genus, Order, Phylum

Answer: (a) and (c) show the correct order.

Question 8: Define the following terms:

(a) Phylum

Answer: A group of closely related classes is called phylum. In the Plant Kingdom; the term phylum has been replaced with division. For example; pisces, amphibia, reptilia, aves and mammalia belong to the Phylum Chordata.

(b) Class

Answer: The group of closely related orders is called class. For example; orders Primata and Carnivora belong to the class Mammalia.

(c) Family

Answer: A group of closely related genera is called a family. For example; potato and chili belong the family Solanaceae. Similarly, the genus Panthera and the genus Felis belong to the family Felidae.

(d) Order

Answer: A group of closely related families is called order. For example; Convolvulaceae and Solanaceae are plant families which belong to the order Polymoniales. Similarly, Felidae and Concidae belong the order Carnivora.

(e) Genus

Answer: A group of closely related species is called genus. Example; Lion (Panthera leo), leopard (Panthera pardus) and tiger (Panthera tigris) are members of the genus Panthera. Similarly, potato, tomato and brinjal belong to the genus Solanum.

Question 9: How is a key helpful in the identification and classification of an organism?

Answer: A pair of two contrasting characters is called key. While identifying a particular species or any other taxon; we need to select one of the characters and reject another. For example; presence or absence of notochord indicates if the animal belongs to chordata or not. Similarly, presence or absence of four limbs indicates if the animal belongs to tetrapoda or not.

Question 10: Illustrate the taxonomical hierarchy with suitable examples of a plant and an animal.

Answer: Following two examples of show taxonomical hierarchy:

Classification of Human

Phylum: Chordata
Class: Mammalia
Order: Primata
Family: Hominidae
Genus: Homo
Species: Homo sapiens

Classification of Mango

Phylum: Angiosperm
Class: Dicotyledons
Order: Sapindales
Family: Anacardiaceae
Genus: Mangifera
Species: Mangifera indica