Here you will find Solutions of Chapter 9 Heredity and Evolution of NCERT Science for Class 10 contains all the main and important topics which have complete and detailed descriptions. Solutions of Chapter 9 Heredity and Evolution of NCERT Science for Class 10 n will help the students of class 10 to understand concepts.
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Solutions of Chapter 9 Heredity and Evolution of NCERT Science for Class 10
You must know the
topics and subtopic of Chapter 9
Heredity and Evolution of NCERT Science for Class 10 before you should go through the Solutions of Chapter 9
Heredity and Evolution of NCERT Science for
Class 10.
Accumulation of Variation During Reproduction
Heredity
Inherited traits
Rules for the Inheritance of Traits- Mendel’s
Contribution
How do these traits get expressed?
Sex determination
Evolution
An
Illustration
Acquired
and Inherited Traits
Speciation
Evolution
and Classification
Tracing
Evolutionary Relationship
Fossils
Evolution
by Stages
Evolution
should not be equated with Progress
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Chapter 9 Heredity and Evolution of
NCERT Science for Class 10 online. The solution is based on the latest syllabus of
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Solutions of Chapter 9 Heredity and Evolution of
NCERT Science for Class 10 Intext questions
Chapter 9 -Heredity and Evolution
TEXTBOOK QUESTIONS
Questions (Page 143)
Q.1If trait
A exists in 10% of a population of an asexually reproducing species and trait
B exists in 60% of the same population, which trait is likely to have arisen
earlier?
Ans. Trait
B that exists in 60% of the population of an asexually reproducing species is
likely to have arisen earlier.
Q.2How does
the creation of variations in a species ensure evolution?
Ans. The
variations provide stability to the population of various species by preventing
them from getting extinct during
adverse conditions. if the Creation of variation favourable then it makes the
organism better fit to an environment and it will ensure the evolution of species.
Questions (Page 147)
Q.1How do
Mendel’s experiments show that traits may be dominant or recessive?
Ans. Mendel performed experiments with pea plants (Pisum
sativum) with contrasting characteristics of tall and dwarf. Mendel performed
cross-pollination and he got all tall
plants in the first generation (F1).
So the characteristics that appeared in first-generation were called dominant
and the characteristics that did not appear were called recessive
Q.2How does
Mendel’s experiment show that traits are inherited independently?
Ans. Mendel
performed a cross between pure tall and pure dwarf pea plants. In the F1
generation, all the plants produced were tall, when plants of the F1
generation were allowed to self-pollinate (self-fertilized) again, then tall and
dwarf plants were obtained in the ratio of 3:1. So this shows that traits of
tallness (T) and dwarfness (t) were inherited independently.
Q.3A man with
blood group A marries a woman with blood group O ad their daughter has blood
group O. Is this information enough to tell you which of the traits-blood group
A or O, is dominant? Why or why not?
Ans. No,
this information is not enough because each individual organism carries two
alleles for one trait. The recessive trait occurs when two alleles are similar.
Blood groups in human beings are determined by the presence of a special protein.
For blood group A, antigen A is formed which is represented by IA.
Perhaps the father may have a heterozygous combination having only one IA
gene. So this information is incomplete to tell which of the traits blood group
A or B is dominant.
Q.4How is the
sex of the child determined in human beings?
Ans. Sex determination in human beings is
determined by sex chromosomes. Sex chromosomes in man ‘XY’ and in female ‘XX’. So the male is heteromorphic and the female is homomorphic. Ovum and sperms are produced
by the process of meiosis. Ovum in female has ‘X’ chromosomes and sperms in males
have chromosomes ‘X’ or ‘Y’.
When ovum fuses with sperm having ‘X’ chromosome then zygote will develop
into a female child (XX) but when sperm having ‘Y’ chromosome fertilize with
ovum(X), then zygote will develop into a male
child (XY).
|
|
X |
X |
|
X |
XX girl |
XX Girl |
|
Y |
XY boy |
XY boy |
Questions (Page 150)
Q.1What are
different ways in which individuals with a particular trait may increase in a
population?
Ans. Accumulation of variation, genetic
drift, the mutation is the different ways by which individuals with a particular
trait may increase in a population
Q.2Why are
traits acquired during the lifetime of an individual not inherited?
Ans. The traits which are passed on to the
DNA of germs cells are inherited to the progeny of the organisms reproducing
sexually. But acquired traits acquired during a lifetime do not pass on the DNA
of germs cells so they are not inherited.
Q.3Why is the
small number of surviving tigers a cause of worry from the point of view of
genetics?
Ans. From the genetics point of view, a smaller number of tigers is a cause of worry because sets of genes will also be
limited and fewer variations will develop in the population and it will be dangerous
for their survival in changing conditions.
Questions (Page 151)
Q.1What
factors could lead to the rise of a new species?
Ans. Speciation: - Origin of new
species from the existing species is called speciation.
The formation of new species from
existing species is mainly due to the
following factors.
1. Accumulation of variations
2. Physical barriers
3. Genetic drift
4. Natural selection
5. Migration
6. Mutation
Accumulation of variations:
- The differences between the individuals of the same species are called
variations. The accumulation of variations over several generations produces
new species or populations.
Physical
barriers: - Populations may get separated by physical barriers like
mountains, rivers, lakes, etc. These isolated groups produce variations that
can produce new species or populations.
Genetic drift:
- Natural calamities or the introduction of new members of the same species in an
area can produce changes in the gene pool of the population and new variations
are produced which can produce new species or populations.
Natural
selection: - Only those individuals of a species that have useful
variations and can adapt to the changes in the environment survive and the
others die. These organisms can produce variations and new species or
populations.
Migration: - Some individuals of a species may
migrate to a new geographical area and adjust to the changes in the environment
there and develop new variations and produce new species or populations.
Mutation:
- Sudden and inherited changes in an organism are called a mutation. Due to
mutation a new species or population.
Q.2Will
geographical isolation be a major factor in the speciation of a
self-pollinating plant species? Why or why not?
Ans. Geographical isolation cannot be a
major factor in the speciation of a self-pollinating plant special because in a
self-pollinated plant, there is no genetic drift and DNA change. There is no
gene flow between two populations So there is little variation possible,
Speciation takes place when variation is combined with geographical isolation.
Q.3Will
geographical isolation be a major factor in the speciation of an organism that
reproduces asexually? Why or why not?
Ans. Geographical isolation is not a major
factor in the speciation of an organism that reproduces asexually because the main role of geographical isolation is to stop gene flow
in population but organisms that
reproduce asexually need not develop variation for speciation. Speciation takes
place when variation is combined with geographical isolation.
Questions (Page 156)
Q.1Give an
example of characteristics being used to determine how close two species are in
evolutionary terms.
Ans. Homologous
organs are being used to determine how close two species are in evolutionary
terms. For example- bats and birds have some similarities in their wings.
Q.2Can the
wing of a butterfly and the wing of a bat be considered homologous organs? Why
or why not?
Ans. No,
the wing of a butterfly and the wing of a bat not be considered homologous
organs, because the designs of the wing of a butterfly and the wing of a bat
are quite different in structure and components. A butterfly is an insect and its
wings are membranous and in bat, the wings are made of skin folds.
Q.3What are
fossils? What do they tell us about the process of evolution?
Ans. Fossils are the remains of dead
organisms and are formed when an organism got buried after death. Fossils tell
us about-
1. Evolution history of organisms.
2. Evolutionary relation between different
organisms.
3. Changes occurred on the earth’s surface.
Questions (Page 158)
Q.1Why are
human beings who look so different from each other in terms of size, colour, and
looks said to belong to the same species?
Ans. The human beings who look so
different from each other in terms of size, colour, and looks, belong to the
same species because there is no reproductive isolation. They can reproduce to
produce fertile generations.
Q.2In
evolutionary terms, can we say which among bacteria, spiders; fish, and
chimpanzees have a ‘better body design? Why or why not?
Ans. Among bacteria, spiders, fish, and
chimpanzees, who has a better body design is not easy to say, because bacteria
is an organism whose simple body design can survive in all environmental
conditions,s and on the other hand more developed and advanced body structure also
exists. So still it is not true that the organisms having the simplest designs are
not having better body designs. Some
bacteria can survive in very hot and very cold climates.
End Exercise Questions
Q.1A Mendelian
experiment consisted of breeding tall pea plants bearing violet flowers with
short pea plants bearing white flowers. The progeny all bore violet flowers,
but almost half of them were short. This suggests that the genetic make-up of
the tall parent can be depicted as:
(a)TTWW
(b)TTww
(c)TtWW
(d)TtWw
Ans. (b) TtWW
Q.2An example
of homologous organs is:
(a)our arm and dog’s fore-leg
(b)our teeth and an elephant’s tusk
(c)potato and runners of
grass
(d)all the above
Ans. (d) all the above
Q.3In
evolutionary terms, we have more in common with:
(a)A Chinese school-boy
(b)A chimpanzee
(c)A spider
(d)A bacterium
Ans. (a)A
Chinese school-boy
Q.4A study
found that children with light-colored eyes are likely to have parents with
light-colored eyes. On this basis, can we say anything about whether the light
eye colour trait is dominant or recessive? Why or why not?
Ans. Yes, children with light coloured eyes are likely to have parents with light-colored
eyes. We can say that the light eye colour trait is dominant because traits are
transmitted from parents to children and a dominant trait appears in the F1
generation.
Q.5How are the
areas of study-evolution and classification-interlinked?
Ans. Classification
means the grouping of organisms on the basis of similar and dissimilar
characteristics. Two species are
more closely related if they have more characteristics in common then it means
they have a more recent ancestor.
Evolution means the
descent with modification.
For example, in a family, a
brother and sister are closely related and they have a recent common ancestor. With
subsequent generations, the variations make organisms more different than their
ancestors. This discussion clearly proves that evolution and classification are
interlinked.
Q.6 Explain the terms analogous and homologous organs with
examples.
Ans. Homologous organs:
- The organs in different organisms are similar in origin (or are embryologically
similar) but perform different functions. For example, the forelimbs of humans
and the wings of birds look different externally but their skeletal structure
is similar.
Analogous organs: - The organs that have different origins but perform
similar functions are called analogous organs For example, the wings of a bird
and a bat are similar in function but this similarity does not mean that these
animals are more closely related.
Q.7 Outline a project which aims to find the dominant coat
colour in dogs.
Ans. Let
coat colour B (Black) is dominant overcoat colour b (white). Suppose a black
homozygous male is mated with a white homozygous female, if in next-generation
all dogs are black then the dominant colour is black.
|
Parent
|
B |
B |
|
b |
Bb |
Bb |
|
b |
Bb |
Bb |
Progeny
with a black coat
Q.8 Explain the importance of fossils in deciding
evolutionary relationships.
Ans. Fossils are the remains of the organism that once existed
on earth. Fossils provide us following important
evolutionary relation –
1. We can learn about the species that are
no longer exist on the earth.
2. They
provide evidence and missing links between the two classes.
3. They are helpful in forming a sequence
of organisms in the pathway of evolution.
4. They provide evidence of the evolution of
organisms.
Q.9 What evidence do we have for the origin of life from
inanimate matter?
Ans. J.B.S. Haldane suggested that life originated from simple
inorganic molecules. He believed that when the earth was formed, it was a hot gaseous
mass containing
1. Elements such as
nitrogen, oxygen, carbon, hydrogen, etc. These elements combined to form
2. Molecules like water,
CO2, methane (CH4), and ammonia (NH3), etc.
3. But when water
formed then the surface of the earth became cool and inorganic substances
4. Interacted with one
another in water to form simple organic molecules such as sugars, fatty acids,
amino acids, etc.
This theory was
proved by Stanley L. Miller and Harold C. Urey. They took a mixture of water, methane,
ammonia, and hydrogen gas in a chamber, and sparks were passed through this
mixture using two electrodes. After one week, 15% of the carbon from methane
was converted into amino acids, sugars, etc. These organic molecules are
polymerized and assembled to form protein molecules that gave rise to life on
earth.
Q.10 Explain how sexual reproduction gives rise to more
variable variations than asexual reproduction. How does this affect the
evolution of those organisms that reproduce sexually?
Ans. In
sexual reproduction, both parents contribute a copy of the same gene, because
each germ cell has a copy of one gene set. So during the course of sexual
reproduction, variations are produced.
Due to the presence of variations the progeny have more chances to survive. In the case
of asexual reproduction, variation is not so frequent and evolution of new
species is also not so frequent.
Q.11 How is the equal genetic contribution of male and female
parents ensured in the progeny?
Ans. A male gamete fuses with a female gamete in
sexual reproduction Each gamete (sperm and ovum) has a single set of genes or
chromosomes. So, a diploid zygote has one set of genes from the father and mother.
In this way, male and female parents ensure equal genetic contribution in the
progeny.
Q.12 Only variations that confer an advantage to an individual
organism will survive in a population. Do you agree with this statement? Why or
why not?
Ans. Yes, we agree with this statement. If the variation
is favourable, it will confer an advantage to the individual organism because
with favourable variation, the organism is well adapted to the environment and if the variation is unfavourable then the organism will be wiped out because of changing environment. So the organisms that are fit in
the competitive environment will be able to survive.
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Important points
1. Variations produced at the time of reproduction
are hereditary.
2. These differences can increase the survival of
the organism.
3. In organisms with sexual reproduction, there are two copies of a gene of a trait. In the absence of these patterns, the characteristic that is expressed is called a dominant trait and the other is called a recessive trait.
4. Various traits are inherited independently in an organism. New combinations are produced in the progeny.
5. The
factors of sex determination are different in different species. The sex of the
offspring in humans depends on what type of chromosome 'X' (for girls) or 'Y'
(for boys) gets from the father.
6. Variations in a species may enable it to survive
or may only contribute to genetic divergence.
7. Changes produced by environmental factors in
somatic tissues are not hereditary.
8. Specification may be due to geographical
separation of variations. Evolutionary relationships can be found in the
classification of organisms.
9. Going Back in Time undefined, The discovery of
common ancestors can give us an idea that at some point in time abiotic matter
originated life.
10. To understand biological evolution, only
the study of the present species is not enough, but fossil studies are also
necessary.
11. Development of complex organs through
intermediate stages for survival.
12. Organs or shapes are adapted for new functions
during the course of bio-evolution. For example, but which were initially
developed to provide heat, later on, they got adapted to fly.
13. Development cannot be said to be a
'progression' of a 'higher' in its 'lower' form. Rather, evolution appears to
have produced more complex physical designs, while the simplest physical
designs are well maintained.
14. From the study of human evolution we come to
know that we are all members of the same species which originated in Africa and
spread in different parts of the world in phases. undefined
Extra questions
Q1. Why are variations less visible among individual plants in a sugarcane
field?
Answer- Sexual reproduction does not take place in
sugarcane, so variations do not arise in it.
Q2. If a trait 'A' is found in 10% of the members of an
asexually reproducing population and 'trait-B' is found in 60% of the organisms
in the same population, then which trait would have arisen first?
Answer- 'Trait-B is found in 60 percent of the
organisms in the same population, which must have arisen earlier.
Q3. How
does the existence of a species increase due to the emergence of variations?
Answer- Due to the emergence of variations, the
organisms of a species are able to adapt themselves according to the
environment, then the existence of that species increases.
Q4. What is the most important outcome of the reproductive process?
Answer- The
most important result of the reproductive process is to have the same design as
the offspring.
Q5. What is the unit that controls traits in organisms called?
Answer – Gene
Q6.How many copies of a set of genes are there in a
somatic cell?
Answer- There are two copies of the set of genes in
a somatic cell.
Q7. How many copies of a set of genes are there in a germ cell?
Ans- The generative cell contains one copy of the
set of genes.
Q8. DNA of a species How is its durability ensured?
Answer- A
pair of chromosomes in the generative cell (gamete) of an organism of a species
is a chromosome. When the fusion of gametes takes place, the number of
chromosomes in the zygote becomes normal again, so that the number of
chromosomes in the offspring remains fixed, which is the DNA of the species.
ensures the durability of
Q9. Name any one organism/animal which changes its gender?
descend - snail
Q10. How is it known that sex determination in snails is not genetic?
Answer- Sex determination in snails is not genetic,
as they change their sex during their lifetime.
Q11. What is the basis of sex determination in humans?
Answer- The basis of sex determination in humans is
genetic.
Q12.Write the trait and gene variant ratio in a single hybrid and double cross-hybridization experiment.
Ans – A hybrid – trait phenotypic ratio –
3:1 undefined Ratio – 1: 2: 1 Double Hybridization – Characteristic Ratio –
9:3: 3:1 Gene Phylotype Ratio –1:2:2: 4:1:2:1:2: 1
Q13. What is Charles Darwin's theory?
Answer: Principle of natural selection
Q14. Who was the first to say that life on earth originated from simple
inorganic substances?
Answer – J.B.S. Haldane
Q15. Write Stanley Miller's experiment.
Answer- Stanley Miller used a special airtight
device called spark release device. In this device, methane, ammonia, hydrogen
and water were transported through high-energy electric sparks (temperatures
below 100°C). The water vapor and heat were provided by boiling water. This
water vapor gradually cooled, and after about a week, the percentage carbon
(methane) formed simple organic compounds. It also synthesized the amino acids
that makeup proteins. On the basis of this experiment, it can be said that
life originated from inorganic substances.
Q16. Where are genes found?
Answer- on the chromosome.
Q17. What is genetic material?
Answer- D.N. a. genetic material.
Q18.A single undefined Why are traits acquired by an organism usually not
inherited in the next generation?
Answer – DNA of germ cell The changes that take
place in it are hereditary in the next generation. Traits acquired by the
organism are not transferred to the DNA.
Q19. Why is the reduction in the number of tigers a matter of concern from the
point of view of heredity?
Answer – The reduction in the number of tigers is a
matter of concern from the point of view of heredity because the reduction in
numbers will result in a reduction in the set of genes so that variations will
not arise during sex reproduction and due to environmental changes, the
survival of the tigers will be at risk.
Q20. What are the factors which are helpful in the emergence of new species? Answer: Mutation, natural selection, etc.
Q21. Can geographical isolation be the main reason for species emergence of plants of self-pollinated species why or why not?
Ans-
Geographic isolation cannot be the main reason for species emergence of plants
of self-pollinated species as it will not cause any change in genes or DNA and
will not produce variations.
Q22. Is Geographical Segregation undefined Species origin of organisms with
asexual reproduction can be the main reason why or why not?
Ans- Geographic isolation cannot be the main reason
for species emergence of asexually reproducing organisms as it will not cause
any change in genes or DNA and will not produce variations.
Q23. Can the wings of a butterfly and a bat be called homologous parts? Why or
why not?
Ans- Wings of a butterfly and a bat cannot be
called homologous parts, because the structure of their wings is not the same.
Q24. Name some residual organs present in human beings.
Ans-
projectile plate, external ear muscles, appendix, etc.
Q25. What are the two variations of the ear lobe in humans?
Answer –
independent ear lobe and fused ear lobe undefined
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