NCERT Exemplar Class 10 Science Solutions Chapter 9 Heredity and Evolution
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CBSE Class 10th Exam Date:01 Jan' 26 - 14 Feb' 26
The Heredity and Evolution chapter is all about how changes occur and are inherited in living beings and how they influence evolution. The main topics in the NCERT Exemplar Class 10 Science Solutions Chapter 9 Heredity and Evolution are Griffith's experiment, Mendel's laws, and the theories of Lamarckism and Darwinism. NCERT Exemplar Solutions not only help the students to overcome board exams, but also help in building a good foundation for future study in biology. Studying through these allows students to get accurate answers of the questions present in their NCERT textbooks.
This Story also Contains
- Detailed Answers to the NCERT Exemplar Class 10 Science Chapter 9 (Multiple Choice Questions)
- Find Answers to NCERT Exemplar Class 10 Science Chapter 9 (Short Answer)
- Access Answers to NCERT Exemplar Class 10 Science Solutions Chapter 9 (Long Answer)
- Approach to Solve NCERT Exemplar Class 10 Science Solutions Chapter 9
- Important Topics of Heredity and Evolution Class 10 NCERT Exemplar
- Advantages of NCERT Exemplar Class 10 Science Chapter 9 Solutions
- Important Question from Heredity and Evolution Class 10 NCERT Exemplar
- NCERT Class 10 Science Exemplar Solutions for Other Chapters
Students need to go through the NCERT Solutions for Class 10 Science to score better marks in the Class 10 Science examination. These solutions provide correct answers and descriptions to each question of the chapter and serve as valuable study guides. Subject experts have provided NCERT Exemplar Class 10 Science Solutions Chapter 9 Heredity and Evolution in a well-understandable language along with well-labelled diagrams. Topics such as patterns of inheritance and the evolution process are required for scoring high marks in board exams as well as in competitive exams.
Detailed Answers to the NCERT Exemplar Class 10 Science Chapter 9 (Multiple Choice Questions)
Different forms of questions, like MCQs, short answers, and long answers with the required diagrams, are provided below. Practising these will help you understand the pattern and these concepts easily and effectively.
Question:1
Exchange of genetic material takes place in
(a) vegetative reproduction
(b) asexual reproduction
(c) sexual reproduction
(d) budding
Answer: (c)
Solution: Sexual reproduction: The exchange of genetic material takes place as genes of two parents are involved, and both the genetic materials are combined to form a new genetic output.Asexual reproduction: no exchange of genetic material takes place as a single parent is involved. Budding and vegetative reproduction are asexual modes of reproduction
Therefore, option (c) is correct.
Question:2
Two pink coloured flowers on crossing resulted in 1 red, 2 pink and 1 white flower progeny. The nature of the cross will be
(a) double fertilization
(b) self pollination
(c) cross fertilization
(d) no fertilization
Answer:(c)
Solution:(a) double fertilization: one female gamete unites with two male gametes.
(b) self-pollination: the transfer of pollen from the anther of a flower to the stigma of the same flower
(c) cross-fertilization: fusion of male and female gametes from different individuals of the same species.
(d) no fertilization: Eggs fail to fertilize
In the question, it is given that two pink coloured flowers on crossing resulted in 1 red, 2 pink and 1 white flower progeny. By the above definitions, nature will be cross-fertilization.
Here, fertilization of a plant using pollen from another plant of the same species is taking place. This is an example of cross-fertilization.
Therefore, option (c) is correct.
Question:3
A cross between a tall plant (TT) and short pea plant (tt) resulted in progeny that were all tall plants because
(a) tallness is the dominant trait
(b) shortness is the dominant trait
(c) tallness is the recessive trait
(d) height of pea plant is not governed by gene ‘T’ or ‘t’
Answer:(a)
Solution:Tallness is a dominant trait, even though there is only one allele of T in the genotype, but the output is tall.
Hence, crossing a tall plant (TT) and a short pea plant (tt) results in all tall plants.
The other trait, which is not shown, is called the recessive trait.
Therefore, option (a) is correct.
Question:4
Which of the following statements is incorrect?
(a) For every hormone, there is a gene.
(b) For every protein, there is a gene.
(c) For the production of every enzyme, there is a gene.
(d) For every molecule of fat, there is a gene
Solution:
Statements (a), (b), (c) are correct.
The incorrect statement is (d), as fat molecules are not related to genes. Fats are long-chain fatty acid.
Therefore, option (d) is the correct answer.
Question:5
If a round, green seeded pea plant (RR yy) is crossed with wrinkled, yellow seeded pea plant, (rr YY) the seeds produced in F1 generation are
(a) round and yellow
(b) round and green
(c) wrinkled and green
(d) wrinkled and yellow
Solution:
The cross between RRyy and rrYY seeds will produce RrYy (round and yellow) seeds in F1 generation, because round and yellow are dominant traits.
Therefore, option (a) is correct.
Question:6
In human males all the chromosomes are paired perfectly exceptone. This/these unpaired chromosome is/are
(i) large chromosome
(ii) small chromosome
(iii) Y chromosome
(iv) X chromosome
(a) (i) and (ii) (b) (iii) only
(c) (iii) and (iv) (d) (ii) and (iv)
Solution:
Humans have two sex chromosomes, X and Y.
In females, two X chromosomes are present, making it a perfect pair.
But in males, one is a normal-sized X chromosome while the other is a short Y chromosome.
Therefore, option (c) is correct.
Question:7
The maleness of a child is determined by
(a) the X chromosome in the zygote
(b) the Y chromosome in the zygote
(c) the cytoplasm of the germ cell, which determines the sex
(d) sex is determined by chance
Solution:
The male outcome of a child is determined by the Y chromosome in the zygote inherited from the father.
If X chromosome is inherited from the father, the zygote will develop into a female.
Therefore, option (b) is correct.
Question:8
A zygote which has an X chromosome inherited from the father will develop into a
(a) boy
(b) girl
(c) X- chromosome does not determine the sex of a child
(d) either boy or girl
Solution:
In humans, the sex of the child is determined by the chromosome inherited by the father.
If the zygote inherits the X chromosome, the zygote will develop into a female.
If the zygote inherits the Y chromosome, the zygote will develop into a male.
Therefore, option (b) is correct.
Question:9
Select the incorrect statement
(a) Frequency of certain genes in a population changes over several generations, resulting in
evolution
(b) Reduction in weight of the organism due to starvation is genetically controlled
(c) Low-weight parents can have heavy-weight progeny
(d) Traits which are not inherited over generations do not cause evolution
Solution:
(a) The change in the heritable characteristics of biological populations over successive generations is called Evolution. So the frequency of certain genes in a population changes over several generations, resulting in evolution. Hence, the statement is correct.
(b) Low weight is not a trait that is genetically controlled or inherited. So, the weight reduction due to starvation will not change the DNA of the germ cells. Hence, the statement is incorrect.
(c) As discussed in option (b), Low weight is not a trait that is genetically controlled or inherited. Hence, low-weight parents may have heavy-weight progeny. Hence, the statement is correct.
(d) The change in the heritable characteristics of biological populations over successive generations is called Evolution. Traits which are not inherited, i.e., the acquired traits are simply changes in non-reproductive tissues, so, cannot be passed on to the DNA of germ cells. Hence, the statement is correct.
Therefore, option (b) is correct.
Question:10
New species may be formed if
(i) DNA undergoes significant changes in germ cells
(ii) chromosome number changes in the gamete
(iii) there is no change in the genetic material
(iv) mating does not take place
(a) (i) and (ii)
(b) (i) and (iii)
(c) (ii), (iii) and (iv)
(d) (i), (ii) and (iii)
Solution:
(i) If DNA undergoes a significant change in germ cells, a new species may be formed. These changes in DNA will be inherited by the germ cells, which pass to the next generation and will be inherited by subsequent generations.
(ii) chromosome number changes in the gamete lead to a change in the gene pool and cause variation.
(iii) If there is no change in the genetic material, a new species will not be formed.
(iv) If mating does not take place, a new species will not be formed
Therefore, option (a) is correct.
Question:11
Two pea plants, one with round green seeds (RRyy) and another with wrinkled yellow (rrYY) seeds, produce F1progeny that have round, yellow (RrYy) seeds. When F1plants are selfed, the F2progeny will have a new combination of characters. Choose the new combination from the following
(i) Round, yellow
(ii) Round, green
(iii) Wrinkled, yellow
(iv) Wrinkled, green
(a) (i) and (ii)
(b) (i) and (iv)
(c) (ii) and (iii)
(d) (i) and (iii)
Solution:
Here, a typical dihybrid cross is given.
Two characters are considered at a time:
- Colour of the seeds (green or yellow)
- Shape of the seeds (round or wrinkled).
So the phenotypic ratio of 9: 3: 3: 1 is obtained.
Round Yellow: Round green: Wrinkled yellow: Wrinkled green = 9:3:3: 1. The two new combinations are round & yellow seeds and wrinkled & green seeds are
Therefore, option (b) is correct.
Question:12
A basket of vegetables contains carrot, potato, radish and tomato. Which of them represent the correct homologous structures?
(a) Carrot and potato
(b) Carrot and tomato
(c) Radish and carrot
(d) Radish and potato
Solution:
The structures that are similar in related organisms because they were inherited from a common ancestor are Homologous structures. These may or may not have the same function as in the descendants.
Radish and carrot represent homologous structures as they have the same structure (or basic design) though they are different species. Both store energy and have modified roots.
Therefore, option (c) is correct.
Question:13
Select the correct statement
(a) Tendril of a pea plant and the phylloclade of Opuntia are homologous
(b) Tendril of a pea plant and the phylloclade of Opuntia are analogous
(c) Wings of birds and limbs of lizards are analogous
(d) Wings of birds and wings of bat are homologous
Solution:
The structures that are similar in related organisms because they were inherited from a common ancestor are Homologous structures. These may or may not have the same function as in the descendants.
(a) Tendril of a pea plant and phylloclade of Opuntia both structures belong to the shoot system and are inherited from a common ancestor. The phylloclade of Opuntia is modified for photosynthesis, and the tendril is meant to provide support to the weak stem. Hence these are homologous.
(b) Analogous structures are similar structures that evolved independently into two living organisms for the same purpose. Tendril of a pea plant and phylloclade of Opuntia are homologous as discussed in part (a).
(c) Analogous structures are similar structures that evolved independently into two living organisms for the same purpose. Wings of birds and limbs of lizards do not have the same purpose, hence these are not analogous.
(d) Bat wings consist of flaps of skin stretched between the bones of the fingers and arm. Bird wings consist of feathers extending all along the arm. These structural dissimilarities suggest that bird wings and bat wings were not inherited from a common ancestor with wings. Hence, these are not homologous.
Therefore, option (a) is correct.
Question:14
If the fossil of an organism is found in the deeper layers of earth, then we can predict that
(a) the extinction of organisms has occurred recently
(b) the extinction of organism has occurred thousands of years ago
(c) the fossil position in the layers of earth is not related to its time of extinction
(d) time of extinction cannot be determined
Solution:
A fossil is any preserved remains, impression, or trace of any once-living thing from a past geological age.
If the fossil of an organism is found in the deeper layers of Earth, then the extinction of the organism is predicted to have occurred thousands of years ago.
The more recent fossils are the ones found closer to the surface.
Therefore, option (b) is correct.
Question:15
Which of the following statements is not true with respect to variation?
(a) All variations in a species have equal chance of survival
(b) Change in genetic composition results in variation
(c) Selection of variants by environmental factors forms the basis of evolutionary processes.
(d) Variation is minimum in asexual reproduction
Solution:
(a) All variations in a species have equal chance of survival: the statement is incorrect. Some variations are too drastic that the new DNA cannot work with it, such as, death of a newborn cell.
(b) Change in genetic composition results in variation: True
(c) Selection of variants by environmental factors forms the basis of evolutionary processes: True
(d) Variation is minimum in asexual reproduction: True
Therefore, option (a) is correct.
Question:16
A trait in an organism is influenced by
(a) paternal DNA only
(b) maternal DNA only
(c) both maternal and paternal DNA
(d) neither by paternal nor by maternal DNA
Solution:
Both maternal and paternal DNA influence the traits of an organism.
Both mother and father pass their genes to their children during sexual reproduction, which determines their traits.
Traits or characteristic features are passed down from one generation to another through genes found on the chromosomes.
Therefore, option (c) is correct.
Question:17
Select the group which shares the maximum number of common characters
(a) two individuals of a species
(b) two species of a genus
(c) two genera of a family
(d) two genera of two families
Solution:
Taxonomic Hierarchy:
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
Hence, two individuals of the same species will share the maximum number of common characters.
Therefore, option (a) is correct.
Question:18
According to the evolutionary theory, the formation of a new species is generally due to
(a) sudden creation by nature
(b) accumulation of variations over several generations
(c) clones formed during asexual reproduction
(d) movement of individuals from one habitat to another
Solution:
The change in the heritable characteristics of biological populations over successive generations is called Evolution.
(a) Sudden creation by nature is not an evolutionary process
(b) Accumulation of variations over several generations forming new species is an evolutionary process. Genetic drift accumulates different changes in sub-populations of a species. In the different geographic locations, natural selection may also operate differently. Eventually, different groups of new species will be formed.
(c) Cloning is the process of producing individuals with identical or virtually identical DNA, either naturally or artificially. It is not an evolutionary process.
(d) Movement of individuals from one habitat to another is not evolution
Therefore, option (b) is correct.
Question:19
From the list given below, select the character which can be acquired but not inherited
(a) colour of eye
(b) colour of skin
(c) size of body
(d) nature of hair
Solution:
- Inherited traits are present in the person since the time of his birth and are passed on from one generation to another
- Acquired traits: A person develops during his lifetime. Acquired traits develop in response to the environment.
- Colour of eye, colour of skin and nature of hair cannot be developed during our lifetime. So these are considered as inherited.
- The size of the body is an acquired trait because it can be changed on the availability of less or more food.
Question:20
The two versions of a trait (character) which are brought in by the male and female gametes are situated on
(a) copies of the same chromosome
(b) two different chromosomes
(c) sex chromosomes
(d) any chromosome
Solution:
The genes are available in various structures or alleles in a sexually reproducing population. These alleles are situated on various copies of the same chromosomes. In an ordinarily diploid sexually reproducing population like humans, every individual has 23 sets of chromosomes. Subsequently, there are two copies of each chromosome.
One chromosome comes from the father through the male gamete and the other chromosome comes from the mother through the female gamete. After fertilization, the zygote is produced having 23 pairs of chromosomes.
Hence, the two versions of a trait are situated on copies of the same chromosome.
Therefore, option (a) is correct.
Question:21
Select the statements that describe characteristics of genes
(i) genes are a specific sequence of bases in a DNA molecule
(ii) a gene does not code for proteins
(iii) in individuals of a given species, a specific gene is located on a particular chromosome
(iv) each chromosome has only one gene
(a) (i) and (ii)
(b) (i) and (iii)
(c) (i) and (iv)
(d) (ii) and (iv)
Solution:
Genes are stretches of DNA found on chromosomes of a cell. A gene contains information for making proteins in a cell. A specific gene is located on a particular chromosome in individuals of a given species.
Therefore, option (b) is correct.
Question:22
In peas, a pure tall plant (TT) is crossed with a short plant (tt). The ratio of pure tall plants to short plants in F2 is
(a) 1 : 3
(b) 3 : 1
(c) 1 : 1
(d) 2 : 1
Solution:
Parent generation TT (pure tall) x tt (pure dwarf)
Gametes T t
F1 generation Tt (heterozygous tall)
F2 generation
F2 Generation Phenotypic ratio = 3:1
Genotypic ratio = 1: 2: 1
Therefore, option (d) is correct
Question:23
The number of pair (s) of sex chromosomes in the zygote of humans is
(a) one (b) two
(c) three (d) four
Solution:
The number of sex chromosomes in the zygote of humans is one pair. It is not always a perfect pair. In females, it is perfect with two X chromosomes. However, in males, there is one X chromosome and one Y chromosome.
Therefore, option (a) is correct.
Question:24
The theory of evolution of species by natural selection was given by
(a) Mendel (b) Darwin
(c) Morgan (d) Lamarck
Solution:
The theory of evolution of species by natural selection was given by Charles Darwin.
Mendel gave the laws of inheritance of traits. Morgan worked on Drosophila melanogaster and gave the concept of linked genes; Lamarck gave the theory of inheritance of acquired characteristics
Therefore, option (b) is correct.
Question:25
Some dinosaurs had feathers, although they could not fly but birds have feathers that help them to fly. In the context of evolution this means that
(a) reptiles have evolved from birds
(b) there is no evolutionary connection between reptiles and birds
(c) feathers are homologous structures in both organisms
(d) birds have evolved from reptiles
Solution:
In the context of evolution, the use of feathers by birds for flying means that birds have evolved from reptiles. Dinosaurs had feathers but could not fly using them. Birds later adapted the feathers for flight. Since dinosaurs were reptiles, this means that birds have evolved from them.
Therefore, option (d) is correct.
Find Answers to NCERT Exemplar Class 10 Science Chapter 9 (Short Answer)
The detailed answers to the Short Answer questions are given below:
Question:26
How is the sex of a newborn determined in humans?
Answer:
Exchange of genetic material takes place as genes of two parents are involved and both the genetic materials are combined to form new genetic output.Humans have two sex chromosomes, X and Y.
In females, two X chromosomes are present, making it a perfect pair.
But in males, one is a normal-sized X chromosome while the other is a short Y chromosome.
In humans, the sex of the child is determined by the chromosome inherited from the father.
If the zygote inherits the X chromosome, the zygote will develop into a female.
If the zygote inherits the Y chromosome, the zygote will develop into a male.
So women are XX, while men are XY
Question:27
Do genetic combination of mothers play a significant role in determining the sex of a new born.
Answer:
Mothers have a pair of X chromosomes. So they do not play a significant role in determining the sex of a newborn.Humans have two sex chromosomes, X and Y.
In females, two X chromosomes are present, making it a perfect pair.
But in males, one is a normal-sized X chromosome while other is a short Y chromosome.
In humans, the sex of the child is determined by the chromosome inherited by the father.
If the zygote inherits X chromosome, the zygote will develop into a female.
If the zygote inherits Y chromosome, the zygote will develop into a male.
All children will inherit an X chromosome from their mother, regardless whether they are boys or girls
Question:28
Mention three important features of fossils which help in the study of evolution.
Answer:
Important features of fossils which help in the study of evolution are(i) Mode of preservation of ancient species is represented by Fossils.
(ii) The relationship between organisms and their ancestors is established using fossils.
(iii) Fossils help in establishing the time period in which organisms lived.
Question:29
Why do all the gametes formed in human females have an X chromosome?
Answer:
Human females have two X chromosomes, called sex chromosomes. During meiosis at the time of gamete formation, one X chromosome enters each gamete. Hence, all the gametes formed in human females possess an X chromosome.Question:30
Answer:
- Humans have two sex chromosomes, X and Y.
- In females, two X chromosomes are present, making it a perfect pair.
- But in males, one is a normal-sized X chromosome while other is a short Y chromosome.
- In humans, sex of the child is determined by chromosome inherited by the father.
- If the zygote inherits X chromosome, the zygote will develop into a female.
- If the zygote inherits Y chromosome, the zygote will develop into a male.
So the zygote receives X chromosome from the female, but from male zygote can receive either X or Y chromosome, which is 50 – 50 probability wise.
Question:31
Answer:
A very small population of a species faces a greater threat of extinction than a larger population because of the following reasons:1. Small population promotes inbreeding.
Production of offspring from the mating or breeding of individuals or organisms that are closely related genetically, is
known as inbreeding.
2. Small population is helpless against abrupt change in climate. Because of genetic drift, odds of species with small
population may wipe out.
3. Small population gets reproductively isolated so no exchange of genes, that would lead to less variations.
Question:32
Answer:
The structures that are similar in related organisms because they were inherited from a common ancestor are Homologous structures. These may or may not have the same function as in the descendants.Examples: forelimbs of reptiles, amphibians, birds and mammals.
Yes, homologous structures are inherited from a common ancestor.
For example,
- Tendril of a pea plant and phylloclade of Opuntia both the structures belong to the shoot system and are inherited from a common ancestor. Phylloclade of Opuntia is modified for photosynthesis and tendril is meant to provide support to the weak stem. Hence these are homologous.
- The mammals as well as birds, reptiles and amphibians all have four limbs. The basic structure of limbs is similar though it has been modified to perform different functions in various vertebrates. Thus, they have evolved from a common ancestor
Question:33
Answer:
Common ancestry may extraordinarily restrict the degree of diversity, e.g., all birds are closely related, they have common ancestors, but birds and reptiles are also related.Animals show immense variety in their structures; they probably have diverse ancestry. If we arrange species according to the evolutionary relationship, we can develop small groups of living beings with ongoing regular predecessors. These are additionally named as super-groups with the most distinct common ancestors. Moreover, we can continue to go in reverse in this arrangement to go to a single species at the earliest reference point of evolutionary time. But having a single ancestor would restrict the diversity seen in the organisms today.
Along these lines, it very well may be said that the occurrence of animals on Earth proposes their diverse ancestry, too.
Question:34
Answer:
Character Contrasting traitsDominant Recessive
(i) seed color - yellow green
(ii) seed shape- round wrinkled
Question:35
Why did Mendel choose the pea plant for his experiments?
Answer:
Mendel chose the pea plant for his experiment for the following reasons- Easy to cultivate
- They have a short life span
- They have sharply defined and contrasting traits (For example, height (tall, dwarf), seed color (yellow-green), etc.)
- These are self-pollinated.
- They have bisexual characteristics
- These have excellent disease resistance
- Have an optimal rate of survival
Question:36
A woman has only daughters. Analyse the situation genetically and provide a suitable explanation.
Answer:
Humans have two sex chromosomes, X and Y.In females, two X chromosomes are present, making it a perfect pair.
But in males, one is a normal-sized X chromosome while the other is a short Y chromosome.
In humans, the sex of the child is determined by the chromosome inherited from the father.
If the zygote inherits the X chromosome, the zygote will develop into a female.
If the zygote inherits the Y chromosome, the zygote will develop into a male.
So, the sex of an infant is determined by the type of sex chromosome contributed by the male gamete.
If a woman has only daughters, this is because the child will have the XX pair of sex chromosomes.
This indicates that in every fusion, the sperm carrying X chromosome fertilized the ovum
Access Answers to NCERT Exemplar Class 10 Science Solutions Chapter 9 (Long Answer)
The detailed answers to the Long Answer questions are given below:
Question:37
Answer:
Yes, the geographical isolation of individuals of a species leads to the formation of a new species.Reproductive isolation is caused by the splitting of existing species into two new species, followed by their geographical isolation. This separation is done by the accumulation of genetic variations. The newly formed groups are isolated by geographical barriers. This in turn, prevents interbreeding between members of different species.
Hence, this causes the isolation of the gene pool of a section of the population from the rest and leads to the formation of new species.
Question:38
Answer:
Evolution is basically the generation of diversity and the moulding of diversity by ecological selection. Additionally, it isn't as though the recently created species are in any capacity better than the older ones.It is only that common choice and hereditary drift have together prompted the arrangement of a population that cannot reproduce with the first one.
The only reformist pattern in evolution is that more and more complex body designs have arisen over time. Nonetheless, once more, it isn't as though the more established plans are inefficient. In fact, one of the least complex living things—bacteria— possess the most inhospitable natural surroundings like hot springs, deep-sea thermal vents and the ice in Antarctica. In other words, human beings are not the peak of development, rather just one more animal variety in the plentiful range of advancing life.
Irrespective of their races, all humans belong to a single species. We can notice features like:
- A common body plan, structure, physiology and metabolism.
- A constant chromosome number, i.e., 46.
- Genetic makeup is also similar; almost 99.9% of DNA is the same in all humans.
- They can freely interbreed to produce offspring.
Evolutionary events indicate the origin of humans from a common African ancestor. Homo sapiens (the earliest members of the human species) can be traced there. On the basis of the above information, we can conclude that all human races seem to have a common ancestor.
Question:40
Differentiate between inherited and acquired characters. Give one example for each type.
Answer:
Differences between inherited and acquired characters
Question:41
Give reasons why acquired characters are not inherited.
Answer:
Acquired characters are traits that are not inherited, i.e., the acquired traits are simply changes in non-reproductive tissues, so, cannot be passed on to the DNA of germ cells.Hence, acquired characters do not produce a change in the genes of germ cells, so they cannot be inherited.
Example: The skills like cycling do not have any genetic changes in the individual who knows it. So it cannot pass from one generation to another as genetic code is the only way organisms pass information to the next generation.
Question:42
Answer:
Morphological structures are easily visible to us. As the name suggests, molecular structures exist at the sub-atomic level. Different biomolecules are required to form an organism. Diversity in morphological structures leads to the diversity of organisms we see around us. Life began in simple forms and gradually developed into many complex organisms. Therefore, morphological structures are considered to have the least stability.
At the molecular level, all life forms are made of the same biomolecules. DNA, proteins, lipids, carbohydrates, etc., are present in all organisms. The structure of DNA is the same in every organism, but the amount of DNA varies from one organism to another. Regardless of the type of organism, a DNA molecule or a protein molecule has the same basic structure. Hence, molecular structures are considered to have high stability.
Question:43
In the following crosses write the characteristics of the progeny
Cross Progeny
(a) RRYY x RRYY
Round, yellow Round, yellow ________
(b) RrYy x Rr Yy
Round, yellow Round, yellow ________
(c) rryy x rryy
wrinkled, green wrinkled, green _______
(d) RRYY x rryy
Round, yellow wrinkled, green ________
Answer:
(a) Parents: RRYY x RRYYGametes: RY x RY
Progeny: All are RRYY (Round Yellow)
(b) Parents: RrYy x RrYy
Gametes: RY; Ry; rY; ry RY; Ry; rY; ry
Progeny: Round yellow, Round green, Wrinkled yellow, Wrinkled green
(c) Parents: rryy x rryy
Gametes: ry ry
Progeny: rryy
All of the progeny is going to be wrinkly green
(d) Parents: RRYY x rryy
Gametes: RY ry
Progeny: RrYy
All of the progeny is going to be round yellow
Question:44
Study the following cross and showing self-pollination in F1, fill in the blank and answer the question that follows
Parents: RRYY × rryy
Round, Yellow wrinkled. green
F1: RrYy × ?
Round, yellow?
Answer:
Self-cross in F1 shows dominant character (law of dominance) in F1 generation.Answer will be: Rr Yy
Round, yellow
Question:45
In question 44, what are the combinations of characters in the F2progeny? What are their ratios?
Answer:
RrYy x RrYyGametes : RY ; Ry ; ry ; ry
Gametes : RY ; Ry ; ry ; ry
Progeny Ratio: Round Yellow: Round green: wrinkled Yellow: wrinkled green
9 : 3 : 3 : 1
Features of the mechanism of inheritance are as follows:
(i) Genes control characters.
(ii) Genes are found on chromosomes.
(iii) Genes may exist in two or more forms. One form may be dominant while the other is recessive.
(iv) Each parent has a pair of genes for each characteristic on a chromosome.
(v) The zygote carries the characteristics of both parents, which are inherited through the genes. It is formed when a male gamete fuses with a female gamete during fertilisation. The zygote has a full set of genes, which leads to variation from one generation to the next.
(vi) Offspring inherit two genes (a pair of genes) for each trait from their parents.
Question:47
Give reasons for the appearance of new combinations of characters in the F2progeny.
Answer:
Law of independent assortment: This is the reason for the appearance of new combinations in the F2 generation. It states that:When two pairs of traits are combined in a hybrid, one pair of characters segregates independently of the other pair of characters.
It indicates that the chances for the pea seeds to be round or wrinkled do not depend on their chances to be yellow or green.
Each pair of alleles is independent of the other pairs.
In a dihybrid cross between two plants having round yellow (RRYY) and wrinkled green seeds (rryy), four types of gametes are produced (RY, Ry, rY, ry). Each of these segregated independent of the other.
Progeny Ratio: Round Yellow: Round green: wrinkled Yellow: wrinkled green
9 : 3 : 3: 1
Also, check the NCERT Books and the NCERT Syllabus here
Approach to Solve NCERT Exemplar Class 10 Science Solutions Chapter 9
To solve the Heredity and Evolution questions effectively, follow these simple steps:
- Understand the Concepts Clearly – Ensure that you have a clear understanding of important concepts such as genes, chromosomes, evolution, and natural selection before trying questions.
- Read Questions Carefully – Read questions thoroughly to avoid errors and answer exactly.
- Use Diagrams Where Necessary – Creating neat and labelled diagrams may assist in explaining your answers more effectively, particularly for inheritance patterns or evolutionary processes.
- Practice with Examples – Practice solving Heredity and Evolution Class 10 NCERT Exemplar from the textbook to gain confidence and enhance problem-solving skills.
- Review and Revise – After solving, always review your answers to rectify any mistakes and reinforce your knowledge of the topic.
NCERT Class 10 Exemplar Solutions for Other Subjects:
Important Topics of Heredity and Evolution Class 10 NCERT Exemplar
The key topics and subtopics covered in the Chapter Heredity:
Main Topic | Subtopics |
Understanding the concept of heredity | |
Accumulation of Variation During Reproduction | How variations are formed and passed on |
Characteristics that are passed from parents to offspring | |
Rules for the Inheritance of Traits | |
Mechanisms that determine the sex of an organism | |
| Evolution | How Life Originated on Earth |
| Evolutionary Patterns | Convergent and Divergent Evolution |
| Human Evolution | Stages in Human Evolution |
Must check the NCERT Solution Subject-wise
Advantages of NCERT Exemplar Class 10 Science Chapter 9 Solutions
The chapter Heredity and Evolution builds a strong conceptual understanding of heredity, traits, and evolutionary processes. With clear explanations, these exemplar problems offer many benefits to students, some of which are given below:
- NCERT Exemplar Class 10 Science Chapter 9 Solutions explain concepts such as traits, variation, dominant-recessive characters, and Mendelian Laws in an easy manner.
- The exemplar problems include both concept-based and application-based questions that improve skills important for board exams and competitive exams.
- Students also gain clarity on processes like speciation, evolution, and natural selection through well-explained answers.
- The exemplar problems make sure that students prepare well for revision, and improve speed and accuracy while answering the heredity and evolution questions.
Important Question from Heredity and Evolution Class 10 NCERT Exemplar
Here is an extra question along with the answer to help students practice and strengthen their understanding of the chapter Heredity and Evolution:
Question 1: A zygote which has an X chromosome inherited from the father will develop into a:
(a) boy
(b) girl
(c) The X chromosome does not determine the sex of a child
(d) Either boy or girl
Answer: The correct answer is option(b), girl
Explanation:
The sex of a child is determined by the combination of sex chromosomes. A father can pass either an X or a Y chromosome. If the zygote gets an X from the father (and an X from the mother), it will be XX, which develops into a girl. If it gets a Y from the father, it will be XY, a boy.
Read more NCERT Notes Subject Wise
NCERT Class 10 Science Exemplar Solutions for Other Chapters
Below mentioned are the chapters to go through:
Frequently Asked Questions (FAQs)
Q: What is the significance of variation in a population?
A:
Variations increase adaptability to changing environments, reduce extinction risk, and drive evolutionary processes through natural selection.
Q: What is the law of segregation and how is it explained in NCERT Exemplar solutions?
A:
The law of segregation states that during gamete formation, alleles for a trait separate so each gamete carries only one allele. Mendel demonstrated this using monohybrid crosses.
Q: How does natural selection contribute to evolution according to NCERT Exemplar?
A:
Natural selection contributes to evolution by favouring individuals with advantageous traits that enhance their survival and reproductive success in a given environment. Over time, these advantageous traits become more common in the population, leading to gradual changes in species as they adapt to their surroundings
Q: Why are sex-linked traits more common in males than in females?
A:
Males have only one X chromosome, so recessive sex-linked traits (e.g., color blindness) are expressed directly, whereas females require two copies of the recessive allele for expression.
Q: How does natural selection contribute to evolution according to NCERT Exemplar?
A:
Natural selection favors individuals with advantageous traits, increasing their survival and reproduction rates. Over time, these traits become more common in the population, driving evolution.
Q: What are homologous and analogous organs? Explain with examples.
A:
- Homologous organs: Similar structure but different function; indicate common ancestry (e.g., forelimbs of humans and bats).
- Analogous organs: Different structure but similar function; indicate convergent evolution (e.g., wings of birds and insects).
Q: How do fossils help in understanding the process of evolution?
A:
Fossils provide evidence of past organisms, showing transitional forms and evolutionary changes over time, helping trace the lineage of species.
Q: What are the important questions from NCERT Exemplar Class 10 Science Chapter 9?
A:
Key questions include:
Mendel’s experiments and laws of inheritance.
Differences between acquired and inherited traits.
Mechanisms of natural selection and speciation.
Role of fossils in evolution.
Homologous and analogous organs.
Q: How does Mendel’s experiment explain the inheritance of traits?
A:
Mendel’s experiments with pea plants demonstrated that traits are inherited through discrete units called genes, following principles like dominance, segregation, and independent assortment.
Q: What is the difference between acquired traits and inherited traits?
A:
Acquired traits: Develop during an organism's lifetime due to environmental influence; not passed to offspring (e.g., muscle development).
Inherited traits: Transmitted genetically from parents to offspring (e.g., eye color).
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Could you please specify us the board of education for which you need the half yearly question papers of class X so that we can help you further.
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CBSE Class 10 Half Yearly Exam Question Paper 2025-26 with Answer Key & Analysis
ICSE Class 10 Half Yearly Sample Papers 2025-26 PDF (All Subjects)
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Hi dear candidate,
Can you please specify the board of education or state for which you need to know the exam pattern and syllabus so that we can guide you accordingly.
Since, most of the boards uses NCERT as base syllabus, you can refer to the link below:
NCERT Syllabus for Class 10 – All Subjects PDF Download 2025-26
Exam pattern:
CBSE 10th New Exam Pattern 2026- Marking Scheme, Subject-Wise Exam Pattern
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The CBSE Class 10th Board Exams for the 2026 session will follow the revised curriculum, emphasizing competency-based questions.
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Conducting Body: Central Board of Secondary Education (CBSE).
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Exam Period: The main theory exams are typically held between February and April 2026.
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Grading: Based on marks in five main subjects plus internal assessment marks (often 20 marks per subject) provided by the school.
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Passing Criteria: You must achieve at least 33% overall in each subject (theory + practical/internal assessment combined) to be declared pass.
Key Preparation Strategy
The most crucial element of your preparation is understanding the exam structure:
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Syllabus: Strictly adhere to the rationalized syllabus released by CBSE for the 2025-26 academic year.
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Practice: Your primary resource should be the latest sample papers and previous year question papers. These accurately reflect the format and types of competency questions being asked.
For the most comprehensive and official announcements, including the detailed time table and access to crucial practice materials, always check the official board updates, as tracked by Careers360: https://school.careers360.com/exams/cbse-class-10th .
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If you want admission to 9th grade under the CBSE board in Andhra Pradesh , visit nearby CBSE affiliated schools during the admission period that is generally from January to April or you can check the official websites of the schools in which you are interested for admission if they are accepting the admissions now .
After deciding the school and getting information about admission deadline from the school you can fill out the admission form with documents submission like your previous report card , transfer certificate and birth certificate , they make take entrance test or interview to confirm your admission
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