Extra Questions for Class 10th: Ch 9 Heredity and Evolution (Science) Important Questions Answer Included

Very Short Answer Questions (VSAQs): 1 Mark

Q1. Define heredity.
Heredity deals with the inheritance of characters from one generation to the next.

Q2. How does the creation of variations in a species promote survival?
Variations increases the adaptability of an organism to its changing environmental conditions.

Q3. Name two human traits that show variations.
Colours of eyes and shape of external ears.

Q4. Which of the two sperm or egg–decides the sex of the child?
The sperm decides the sex of the child.

Q5. The forelimbs of frog, reptiles, birds and arms of man show the same basic design. What kind of organs are these?
Homologous organs.

Short Answer Questions-I (SAQs-I): 2 Marks

Q1. What is microevolutions?


Microevolutions is the evolution that takes place on a relatively small scale at the population level and can change the common characteristics of particular species.

Q2. What is speciation?


Speciation is the process of formation of a new species from the already existing species by accumulation of variations, natural selection, gene flow, genetic drift, etc.

Q3. How can we trace evolutionary relationships?


Evolutionary relationships can be traced by studying fossils, by studying homologous and analogous organs, by comparing the embryos of different animals and by comparing the DNA’s of different species.

Q4. What term did Mendel use for genes? Where are the genes located?


Mendel used the term ‘factors’ for genes. Genes are portions of DNA which code for a single protein.

Q5. How many pairs of chromosomes do human beings have, specify the types of chromosomes also?


Human beings have 23 pairs of chromosomes the first 22 pairs are called autosomes are similar in males and females. The 23rd pair is called the sex chromosome. In males it is XY and in females it is XX.

Short Answer Questions-II (SAQs-II): 3 Marks

Q1. What is the effect of DNA copying which is not perfectly accurate on the reproduction process?


If DNA copying is not perfectly accurate then the variations occurs among the species of same organisms.

Q2. Define variation in relation to a species: Why is variation beneficial is the species.


Variations are differences that occur between the organisms of the same species in spite of the same basic features.
Variation in species promotes survival of an organism in changing environment by increasing the adaptability.

Q3. ‘‘Variations that confer an advantage to an individual organism only will survive in population’’. Justify.


Variation is the difference in the characters or traits among the individuals of a species. Sexual reproduction of organisms produces variation. The variations produced in organisms during successive generations gets accumulated in the organism. The significance of variations shows up only if it continues to be inherited by the offspring for several generation.

Q4. What is speciation? How does it occur?


Formation of new species from the existing ones over the period of time is called speciation.
Speciation takes place due to gene flow, genetic drift, reproductive isolation and finally natural selection. 

Long Answer Questions (LAQs): 5 Marks

Q1. How do we know how old fossils are?


We can find the relative of the fossil by the depth at which the fossil is found. The ones that are found near the surface are more recent than the fossils found in the deeper layer.
The second way of dating fossils in detecting the ratios of different isotopes of the same element in the fossils material.

Q2. (i) What is genetics?
(ii) Give the common name of the plant on which Mendel performed its experiments.
(iii) What for did Mendel use the term factors and what are these factors called now?
(iv) What are genes? Where are the genes located?


(i) Science which deals with the study of heredity and variations is called genetic.
(ii) Pea plant.
(iii) Mendel used the term factors for ‘genes’.
(iv) Genes is the unit of inheritance. It is a part of the chromosome which controls the appearance of a set of hereditary character. Genes are located on the chromosome.

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