Board Based Questions with answer: X Chapter : Heredity and Evolution
Q. What is heredity?
Ans:- Heredity refers to the transmission of characters or traits from the parents to their offspring.
Q. What do you understand by evolution?
Ans:-Evolution is the sequence of gradual changes which takes place in the primitive organisms over million of years in which new species are produced.
Q. What is a gene?
Ans:- Gene is a small segment of DNA on a chromosome occupying specific position in which is a hereditary determinant or unit of a biological function.
Q. With the help of suitable examples, explain why certain traits cannot be passed on to the next generation. What are such traits called?
The traits which are acquired during the lifetime of a person are called acquired traits. These traits involve changes in non reproductive cells (somatic cells) which are not transferred to germ cells. So, these traits cannot be passed on to the next generation. For example: Learning skills like swimming, dancing, cooking, body building, etc are acquired traits and cannot be passed on to the next generation.
Q. "A trait may be inherited, but may not be expressed." Justify this statement with the help of a suitable example.
Ans: When a tall plant was crossed with a short plant, the first (F1) generation plants were all tall. But when the F1 generation plants were crossed, the second (F2) generation plants were not all tall: there were both tall and short plants.
This shows that the F1 plants had inherited their trait from the short plants but did not express it in the presence of the tallness, and had transferred it to the next generation.
Q. 'It is a matter of chance whether a couple will give birth to a male child or a female child." Justify this statement with the help of a flow chart showing the fusion of sex chromosomes.
Ans: Sex is determined at the time of fertilization and the two sexes are produced in approximately equal numbers. A human male has XY sex-chromosomes and produces two types of sperms (heterogametic). Either with X-chromosome or with Y-chromosome.
A human female has XX sex-chromosomes and produce ova of one type (homogametic) all with X-chromosomes.
Parents Male Female
Gametes X Y X
Progeny XX XY
Female (50%) Male (50%) Q.What are homologous organs? How do they provide evidence in support of evolution? Ans:- Homologous organs are those organs which have the same basic structure and developmental origin but have different functions and appearance.
Homologous organs support evolution:
(i) The similarities of structure and origin of organs indicate that all vertebrates had common ancestors. For example, the forelimbs of humans, whale and bat show structural similarities but functional dissimilarities. Forelimbs in humans used for grasping or holding the things, in whale for swimming and in bat for flying. (ii) All the organs and systems of the vertebrates show fundamental similarities i.e. homology, which indicate towards common ancestry. Thus, homologous point that organic evolution has taken place. more is added soon