Ncert chapter heredity and evolution class X you can find questions for exam preparation and there is lot of questions based on heredity and evolution chapter for it is doc file it contain short or long answer type question and it is like question paper of school

1. C l a s s : X t h
HEREDITY & EVOLUTION P a g e | 1 of 8
1. “father of genetics” : Gregor Johann Mendel
2. DNA was isolated by Frederick Meisherfor the very first time.
3. Heredity is the transference of the characters and traits from one generation to
other.
4. Miller and Urey provided the experimental evidence to supportthe theory of
origin of life from in animate matter.
5. Sex determination is regulated by environmental factors in turtle and lizard.
6. Gene:It is a segmentof DNA which is located on DNA and act as the
information carriers from one generation to another.
7. What are the features that Archaeopteyrx has in common to the reptiles?
Ans: Archaeopteyrxhas teeth, scales on the bodyand tail like a reptile.
8. What does the presence of 21st extra chromosome cause?
Ans: The presence of 21st extra chromosome causes Down's syndrome.The presence
of this chromosomecauses mental disorderin the child.
9. In what way are the off springs produced through sexual reproduction different
from those produced by asexual reproduction?
Ans: Asexual reproduction produces identical offspringwhile sexual reproduction
does not produce offspring that are exactly similar to the parents.
10.Why is the decreasing number of surviving tigers a cause of worry from the
point of view of genetics?
Ans: As the populationof tigers is decreasing,there is a loss of genes from the gene
pool and hence,there can’t be recombinationand variations,thus no evolution.
11.When Mendel crossed a Tall plant with a dwarf plant, no medium height plants
were obtained in F1 generation. Why?
Ans No medium heightplants were obtained in F1 generation because dominant
genes express themselves and suppress the effect of recessive genes.There is no
mixing of alleles in the F1 generation.
12. Differentiate between homologous and analogous organs.
(Ans)
HOMOLOGOUS ORGANS ANALOGOUS ORGANS
The organswith similar structure and
origin but different functions are
known as homologous organs.
The organs with similar function but
different structures and origin are known
as analogous organs.
Example:forelimbs of frog, wings of
birds, forelimbs of man.
Example:wings of butterfly, wings of a
bird.
13. What do you mean by organic evolution?

2. C l a s s : X t h
HEREDITY & EVOLUTION P a g e | 2 of 8
Ans The branch of science which deals with wide variety of organisms and gradual
change occurring in them since beginningof life is known as organicevolution.
14. Are forelimbs of man and frog analogous organs? Why or why not?
Ans No, forelimbs of man and frog are not analogous organs becausethey are
similar in structure and origin but differentin function. Forelimbs offrog are used
for jumpingand hoppingwhile in man these areused for walking.
15. What are vestigial organs? Give examples.
(Ans) The organs which are presentin the bodybut are functionless are known as
vestigial organs.These organs are homologousto the organs which were functioning
in our ancestors.For example:Vermiform appendixin human beings.
16. What do you mean by autosomes?
Ans: Autosomes are the chromosomes which are associated with the functioningof
the cells and determinationof characters and traits of the individual.There are22
pairs of autosomal chromosomesin human beings.
17. Which abnormal behavior of chromosomes cause Down’s syndrome?
Ans: A 21st extra chromosomecauses Down'ssyndrome.It is a chromosomal
disordercaused by the presence of all or part of an extra 21st chromosome.It is also
known as trisomy 21.
18. Explain Speciation. How does geographical isolation results in speciation?
Ans Speciation is the evolutionaryprocess by which new biological species arise.
When the numberof variations accumulates in a generation,the process may lead to
birth of new species entirelydifferent from the existing ones.
Geographicisolation is the separationof two (or more) biological populations bya
geographical barriereg. river, mountain range,ocean,desert etc. The effect of
geographicisolation is that the two populations are subjected to different selection
pressures and gene flow betweenthem would cease and the two separate populations
would evolve independentlyas different species.
19. Why are the traits acquired during the lifetime of an individual not inherited?
(Ans) Traits acquired during the lifetime of an individual are not inherited because
change in non-reproductive tissue or somatic cells cannotbe passed on to the DNA of
the germ cells. Thus,the acquired trait will be eliminated with the death of the
individual.It is therefore non-heritableand cannotbe passed on to its progeny.
20. How can we calculate the age of a fossil?
(Ans) There are two methods of detectingfossil’s age:

3. C l a s s : X t h
HEREDITY & EVOLUTION P a g e | 3 of 8
i. Relative method:When we dig into the earth, the fossils we find closer to the
surface are more recent than the fossils we find in the deeperlayers.
ii. By detecting the ratios of differentisotopes of the same elementin the fossil
material.
21. (i) State one of the evolutionary forces that lead to the origin of a new species
according to the synthetic theory of evolution.
(ii) What is the evolutionary significance of Archaeopteryx?
Ans (i) Origin of new species is based on natural selection acting on genetic
variations that appearamongthe members of a population.
(ii) Archaeopteryxis the connectinglink between reptiles and birds. It has both
reptilian and avian features.
22. a) Arrange the following according to their evolutionary closeness: Broccoli,
cauliflower, wild cabbage, cabbage, gorilla
b) Whose DNA among the above do you think is most similar to that of humans.
Ans a) Wild cabbage - Cabbage- Broccoli - Cauliflower.
b) DNA of gorilla is most similarto that of humans.
23.What are fossils? Of what interest are fossils to the evolutionary biologists?
Ans A fossil is the remnantor impression ofan organism that lived in the past.
Evolutionarybiologists study fossils for understandingthe phylogenyand the
evolutionaryhistory. The fossil records help in buildinga broad historical sequence
of the biological evolution.
24. What evidence does fossil provide about our evolution?
Ans Fossils are the petrified remains of the ancientlife found preserved in rocks.
The fossils provide evidences aboutour evolution.Forexample:A bird called
Archaeopteyrxhas features of birds as well as reptiles. It has wings and beaklike a
bird but teeth, scales on the body and tail like a reptile.
25. How does the mechanism of heredity work?
Ans CellularDNA (genes) is the information source which regulates metabolism
and makes protein in the cell. It also controls the characters of the progeny.During
sexual reproduction,both the parents contribute equallyto the DNA of the progeny.
Thus all the cells have two copies of chromosomes,one from male and the other from
female.When the two germ cells combine they maintain the total numberof
chromosomes and ensure the stabilityof DNA of the species. Thus the progeny
inherits the traits of the parents.

4. C l a s s : X t h
HEREDITY & EVOLUTION P a g e | 4 of 8
26. Who gave the concept of Natural selection? How does the process of natural
selection relate to organic evolution?
Ans The theory of Natural selection was proposed by Charles Darwin in 1859.
Natural selection is the process by which favorable heritable traits become more
common in successive generationsof a populationof reproducingorganisms and
unfavorableheritable traits become less common,due to differential reproduction of
genotypes.
According to Darwin's theorydue to suitabilityof environmentthere is an increase in
population.This leads to struggle for existence resultingin survival of the fittest and
origin of species,which is termed as organic evolution.
27. Explain DNA’s utility in the process of reproduction of the cell.
It carries genetic information and required by the cells to divide and produce
proteins for regulation, structural and functional roles.During the gamete formation,
DNA creates its exact copies which are passed to the gametes.The fusion of male and
female gamete results in the developmentof variations.Thus, it is the DNA which
acts as the blue print that is passed from generation to generation.
28. (a) What is the function of genes in an organism?
(b) Who proposed the theory of natural selection? Why was this theory criticized?
(Ans) (a) Genes are the segments of DNA which control the traits and
characteristics of an individual.
(b) Darwin proposed the theory of natural selection.Darwin’s theoryof natural
selection was unable to explain mechanism for inheritance of traits from one
generation to the next.
29. We have 23 pairs of chromosomes but still numerous characters are found in
humans. How can we justify this?
Ans There are only23 pairs of chromosomes in humans,but30,000 to 40,000 genes
are presentin the DNA. This implies that each chromosome carries numerous genes
on it. These genes are responsiblefor all the characteristic features.This is the
reason that we have numerous characters,definitelyexceeding46 in number.
30. What are the causes of variations in the clones?
Ans Causes of variations in the clones are:
i. Inaccuracies during DNA copying.
ii. Effect of environmenttermed as acquired variation.
iii. Mutations are sudden stable changes thatare discontinuousinheritableas
produced due to the changes in genetic make-up.
31. Is it true to say evolution is progressive from lower forms to higher forms.
Ans Evolution can not be said to 'progress' from lower forms to higherforms.
Rather, evolution seemsto have given rise to more complex bodydesigns even

5. C l a s s : X t h
HEREDITY & EVOLUTION P a g e | 5 of 8
while simpler bodydesigns continue to flourish and grow. Many simplerand older
body designs still survive. Thus, there is no real progress in the evolution,but only
more complexbody designs have emerged over time.
32. In human beings, blue eye colour is recessive to brown eye colour. If a brown
eyed man has a blue eyed mother, then find:
a) What are the possible genotypes of his father?
b) What is the genotype of the man and his mother?
(Ans) a) Possible genotypesof the father are BB, Bb
b) Genotype of the man: Bb
Genotype of the mother: bb
33. Distinguish between acquired and inherited traits, giving one example of each.
Ans
Acquired trait Inherited trait
A trait (or characteristic) of an organism
that is ‘not inherited’ but develops in
response to the environmentis called an
acquired trait.
A trait (or characteristic) of an organism
that is caused by a change in its genes
(or DNA) is called an inherited trait.
The traits of an organism cannotbe
passed on to its future generations.
The inherited traits of an organism are
passed on to its future generations.
E.g. low weight of beetle,cut tail of a
mouse.
E.g., red colour of beetles,fur coat of
guinea pigs.
34. What is Darwin’s theory of evolution?
Ans According to Darwin's theory of evolution:
(i) Within any population,there is natural variation.
(ii) In spite of reproduction,the population becomes fairly constant.
(iii) This is due to the struggle between the individuals of various species for food,
space and mate.
(iv) Due to this struggle, only the better ones are selected by nature.
(v) The selected individuals pass on their favourable variations to their offsprings.
(vi) These variations whenaccumulated overa long period of time lead to origin of
new species.
35. A boy has parents with two different hair colors: one with red hair and the other
with black hair. The boy has black hair. If we consider the black colour
dominating over the red colour, what could be the possible genotypes of the boy?
(c) Case-I Let BB be the genotype of father and bb of mother.

6. C l a s s : X t h
HEREDITY & EVOLUTION P a g e | 6 of 8
Their offspring will be of followinggenotype:
B B
b Bb Bb
b Bb Bb
The possible genotype of the boy will be:- Bb
The boy will have black hair colour as it is the dominantallele.
Case-II Let Bb be the genotype of father and bb the genotype of mother.
B b
b Bb bb
b Bb bb
The possible genotypes ofthe boy will be:
2: Bb 2: bb
Phenotype:There are 50% chances of boy havingblack hair and 50% chances of boy
havingred hair.
As the boyhas black hair, the genotype will have to be Bb.
36. An elephant learns a trick at the circus. Will his children also know the trick by
birth? Support your answer with reasons.
Ans A trick that an elephantlearns at a circus is not inherited by its progeny
because it is an acquired trait.
Any trait that does not change the genome of an organism will not be inherited.In
this case, the trait is knowledgethat is acquired over the life time of an organism.It
is just like a cut on skin, which will not be inherited.
37. What are the chances of having a baby boy in a marriage between a man with
blood group O and a woman with blood group AB? Give reasons.
Ans In any human marriage betweena man and a woman,the chances of a baby
boy is 50%.This is irrespective of any other inheritablecharacters presentin the
parents.So, whateverbe the blood group, the chances of a baby boy will be 50%.
38. Do you think adaptations can bring about evolution? How?
Ans Adaptations can bring aboutevolution in a populationif the environmental
conditions causingthose adaptationspersist. Adaptations are inheritable traits and
will be carried from one generationto next changing the whole population.This
creates a uniform populationat each generation which are different from the parent
generation.This is evolution.

7. C l a s s : X t h
HEREDITY & EVOLUTION P a g e | 7 of 8
39. What is natural selection? How can it help an organism to be ‘selected’?
(Ans) Natural selection is the selection process that occurs when there is an
environmental conditionprevailingin a geographical area.The organisms residingat
that area will have to fight that condition for survival. Only those which are suited to
withstand that condition will survive. Others will be eliminated.The ones that
survive will reproduce and their numberwill increase day by day. Thus, they are
‘selected’ in the particular environmental condition.
40. How can we say that there is no ‘progress’ in the concept of evolution?
Ans Evolution means creation of diversity (in potential individuals)and nurturing
that diversity to suit in the changingenvironment.Eventuallyif the environmental
conditions persist, the diversity survives, if not, it gives way to anothermore suited
variation.
Thus,evolution does not indicate progress; it only indicates survival of one diversity
or the other.
41. Where in the world did human beings originate and in what form?
Ans Human beings originated in the African continent.The first human being
resemblingmodern humans appeared in Africa and is now called Australopithecine.
42.How are wings of a sparrow and flippers of a whale related?
Ans The wings of a sparrow and flippers of a whale on anatomical study shows
similar type of bone composition.Thus,though they perform different functions,they
have a same origin and have diversified in the course of evolution later on.
Thus,these two are homologous organs.
43. What do you understand by evidences of evolution? Give three examples.
(Ans) Evidences of evolution mean those specimens orcharacters which indicate an
evolutionaryrelationshipbetweentwo organisms.
Three examples include:
Fossil records , Anatomical similarities Geographical distribution
44. What is excavation and how is it related to study of evolution?
Ans Excavation means the digging out of fossil specimens from the earth’s crust.
Careful excavation will give very intact remains of hard structures in the body of the
specimen. This can be used to study evolution as they are proofs of the existence of
that specimen in the remote past.