NCERT Class 11-Biology: Chapter – 1 the Living World Part 4 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Question 9:

Properties of cell organelles are not always found in the molecular constituents of cell organelles. Justify.


The cells usually have the same composition and they are made of similar molecules. All the molecules together in a particular fashion build up different cell organelle with specific functions. The constituents remain the same but the outcome or final product, function and purpose changes. Hence, properties of the cell organelles are not always found in the constituents

Question 10:

The number and kinds of organism is not constant. How do you explain this statement?


This question needs to be looked upon from two perspectives, i.e.. number and variety. For any organism; the population cannot remain constant. In some of the generations, pollution can be more because of favorable condition. In some other generations, population can be less because of unfavorable conditions. The kinds of organism cannot be constant because evolution is a never ending process. In every era new species come into origin and some old species become extinct.

Long Answer Type Questions

Question 1:

What is meant by living? Give any four defining features of life forms.


The living organism exhibit distinctive characteristics, which are as follows

(i) Growth All living organisms grow in size as well as in number. Plants show growth all through their life whereas animals up to a certain growth period after which growth ceases.

(ii) Reproduction The process of reproduction is essential for the continuity of life on earth. Every organism whether unicellular or multicellular gives rise to an individual of its own kind. Lower organisms usually reproduce asexually, e. g. , Hydra, fungi, yeast, etc. Sexual reproduction is found in advanced group of organisms, which involves two parents. In Amoeba growth and reproduction however is synonymous.

(iii) Metabolism There are thousands of enzymatically controlled reactions occurring in all living cells. These are synthesising 9anabolic) and breaking down (catabolic) reactions. Hence, it is the most important characteristic of living organisms.

(iv) Response to stimuli Consciousness and response to stimulus is the defining property of all living organisms. Plants respond to light, water temperature. Unicellular organisms also sense their environment and respond accordingly.

(v) Cellular organisation the cellular organisation of the body is the defining feature of life forms. Cells work together in hierarchial manner group of cells make tissues, tissues make organs, and organs make systems, systems when work in co-ordination form an individual. So, we can say living organisms are self-replicating, evolving and capable of responding to external stimuli.

Question 2:

A scientist has come across a plant which he feels is a new species. How will he go about its identification, classification and nomenclature.


The man of science can initial determine the family to that the plant belongs. He can more follow the given steps

(i) Exploitation genus key, the genus is known.

(ii) Exploitation species key, identification is administered.

(iii) Because the genus is thought, the species is provided currently with a Latinised name as per tips.

(iv) An example or hole kind is placed during a recognised herbarium or repository.

(v) Name, description and report-of the invention is printed during a putative scientific journal.

Question 3:

Brassica Campestris linn

a. Give the common name of the plant.

b. What do the first two parts of the name denote?

c. Why are they written in italics?

d. What is the meaning of linn written at the end of the name?


(a) Common name of the plant is mustard.

(b) The first part of the name denotes the generic name and the second part is the species name of the plant.

(c) According to ICBN, all scientific names are comprised of one generic name followed by a species name, which have to be written in italics always. It is a rule of bionomial nomenclature.

(d) Linn means Linnaeus was the first to discover the plant. He identified, named and classified the plant, so credit is given to him by adding suffix ‘Linn’ , after the scientific name B. campestris Linn.

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