Assertion Reason Science CBSE 10th Chapter 9: Heredity and Evolution

Assertion Reason Science CBSE Class 10 Chapter 9: Heredity and Evolution, To solve assertion reason type questions of science, deeper understanding of concept about our reproduction is required. In order to help the student in solving Assertion Reason type of questions, detailed process is explained.

How to solve Assertion Reason Type Questions ?
In Assertion-Reason type of question, two statements are given, first is Assertion and second is called Reason. Student must have to think critically about both the statements in Assertion Reason Questions, since it combines multiple choice questions and true/false type of questions which requires a higher level of understanding.

In assertion reason type of questions, all 5 options are same for each question, which are as:

(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).
(b) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).
(c) Assertion (A) is true but reason (R) is false.
(d) Assertion (A) is false but reason (R) is true.
(e) Both Assertion and Reason are false.

Then a question haunts in every student’s mind, which option is correct and when?
This can be understood clearly with the following table:

Assertion (A)Reason (R)MCQ Options (Fixed for all questions)
If TrueTrue(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).
If TrueTrue(b) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).
If TrueFalse(c) Assertion (A) is true but reason (R) is false.
If FalseTrue(d) Assertion (A) is false but reason (R) is true.
If FalseFalse(e) Both Assertion and Reason are false.

Now, lets practice some Assertion Reason Questions of Science Chapter 9: Heredity and Evolution.

Directions: Mark the option which is most suitable :
(a) If both assertion and reason are true and reason is the correct explanation of assertion.
(b) If both assertion and reason are true but reason is not the correct explanation of assertion.
(c) If assertion is true but reason is false.
(d) If both assertion and reason are false.

Question.1.
Assertion : Mendel chose a number of varieties of garden pea as plant material for his experiments.
Reason : Garden pea has well defined characters and was bisexual.

(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).

Explanation: Mendel chose garden pea as plant material for his experiment because garden pea plants were easily available/they grow in one season/fertilization was easy.

Question.2.
Assertion : Ear muscles of external ear in man are poorly developed.
Reason : These muscles are useful which move external ear freely to detect sound efficiently.

(c) Assertion (A) is true but reason (R) is false.

Question.3.
Assertion : The establishment of reproductive isolations in an event of biological significance.
Reason : In the absence of reproductive isolation species can merge into single population.

(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).

Question.4.
Assertion : The sex of a child is determined by the mother.
Reason : Humans have two types of sex chromosomes: XX and XY.

(d) Assertion (A) is false but reason (R) is true.

Question.5.
Assertion : In humans, males play an important role in determining the sex of the child.
Reason : Males have two X chromosomes.

(c) Assertion (A) is true but reason (R) is false.

Explanation: Sex of a child is dependent on the type of the male gamete that fuses with the female gamete. Human beings possess 23 pairs of chromosomes. Out of these, 22 pairs are known as autosomes, while the remaining one pair comprises sex chromosomes (XX in females and XY in males). At the time of fertilisation, tha egg cell fuses with the sperm cell, resulting in the formation of the zygote. If the egg cell carrying an X chromosome fuses with the sperm carrying an X chromosome, the resulting child would be a girl. If the egg cell carrying an X chromosome fuses with the sperm carrying a Y chromosome, the resulting child would be a boy.

Question.6.
Assertion : DNA finger printing is a method in which polymerase chain reaction followed by DNA probe is used.
Reason : A DNA finger print is inherited and therefore, resembles that of parents.

(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).

Question.7.
Assertion : The birds have large, light spongy bones with air sacs.
Reason : These adaptations help them during flight.

(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).

Question.8.
Assertion : We have lost all the direct evidence of origin of life.
Reason : The persons responsible for protecting evidences were not skilled.

(c) Assertion (A) is true but reason (R) is false.

Question.9.
Assertion : Variations are seen in offspring produced by asexual reproduction.
Reason : DNA molecule generated by replication is not exactly identical to original DNA.

(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).

Question.10.
Assertion : Although living organism always arise from other living organism,, life should certainly have had a beginning.
Reason : The study of the conditions and the mechanisms involved in the creation of most primitive living structures on earth is actually the problem of origin of life.

(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).

Question.11.
Assertion : Wings of butterfly and wings of bat are analogous organs.
Reason : Analogous organs have different origin and structural plan but same function.

(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).

Explanation: Wings of butterfly and wings of bat though they perform similar function, they have different origin/basic structure. Hence, they are known as analogous organs.

Question.12.
Assertion : Mendel selected the pea plant for his experiments.
Reason : Pea plant is cross-pollinating and has unisexual flowers.

(a) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).

Question.13.
Assertion : The genetic complement of an organism is called genotype.
Reason : Genotype is the type of hereditary properties of an organism.

(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).

Explanation: Genotype of the organism include all dominant and recessive characters.

Question.14.
Assertion : Learning a skill such as dance and music is an acquired trait.
Reason : Acquired traits develops in the life time of an individual and do not pass to the progeny.

(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).

Explanation: Traits which develop in the life time of an individual and do not pass to the progeny are called acquired traits. Learning a skill such as dance/music/loss of body parts/weight etc. are example of acquired traits.

Question.15.
Assertion : Traits like eye colour or height are inherited traits.
Reason : Inherited traits are not transferred from parents to young ones.

(c) Assertion (A) is true but reason (R) is false.

Explanation: Eye colour and height are genetically inherited traits, as these are expressed by genes. Inherited traits are the traits which are transferred from parents to young ones. Acquired traits are the characters that are acquired by the individual during its lifetime. These traits cannot be inherited. For example, if a wrestler develops large muscles due to his training program that does not mean it will be passed on to his offspring.

Question.16.
Assertion : Fossils are remains of dead organisms.
Reason : It is helpful in study of evolution.

(b) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).

Explanation: Fossils are remains of hard parts of the past individuals in the strata of earth. It help in tracing evolutionary pathways.

Question.17.
Assertion : A geneticist crossed two pea plants and got 50% tall and 50% dwarf in the progeny.
Reason : One plant was heterozygous tall and the other was dwarf.

(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).

Question.18.
Assertion : Evolution is called as organic evolution.
Reason : Evolution involves the living organisms.

(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).

Explanation: Evolution is called as organic evolution, because it involves the living organisms.

Question.19.
Assertion : Dominant allele is an allele whose phenotype expresses even in the presence of another allele of that gene.
Reason : It is represented by a capital letter, e.g. T.

(b) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).

Explanation: Dominant allele is an allele whose phenotype will be expressed even in the presence of another allele of that gene. It is represented by a capital letter, e.g. T. Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.

Question.20.
Assertion : Forelimbs of vertebrates are homologous organs.
Reason : Analogous organs have same origin but different functions.

(c) Assertion (A) is true but reason (R) is false.

Explanation: Forelimbs of vertebrates are homologous organs. Analogous organs have different origin but show similar appearance.

Question.21.
Assertion : The sex of the children will be determined by chromosome received from the father.
Reason : A human male has one X and one Y -chromosome.

(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).

Explanation: If a child inherits X – chromosome from the father will be a girl and one who inherits a Y – chromosome will be a boy.

Question.22.
Assertion : Among the primates, chimpanzee is the closest relative of the present day humans.
Reason : The banding pattern in the autosome number 3 and 6 of man and chimpanzee is remarkably similar.

(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).

Explanation: The banding pattern seen on stained chromosomes from humans and chimpanzee show striking similarities which indicates that they have evolutionary relationships (cytogenetic evidence).

Question.23.
Assertion : Human ancestors never used their tails and so the tail expressing gene has disappeared in them.
Reason : Lamarck’s theory of evolution is popularly called theory of continuity of germ plasm.

(c) Assertion (A) is true but reason (R) is false.

Explanation: According to Lamark’s theory, continuous disuse of organs make them weak. The theory of continuity of germplasm was given by Weismann.

Question.24.
Assertion : Speciation is the process of formation of a new species from a pre-existing one.
Reason : Mutation plays a role in speciation.

(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).

Explanation: Speciation is an evolutionary process by which new species arise. One of the factors that lead to speciation is mutation.

Question.25.
Assertion : Mutation is sudden change in the genetic material.
Reason : Variation is useful for the survival of species over time.

(b) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).

Question.26.
Assertion : Changes in non-reproductive tissues can be passed on the the DNA of the germ cells.
Reason : Inherited traits include the traits developed during the lifetime of an individual that cannot be passed on to its propeny.

(d) Assertion (A) is false but reason (R) is true.

Explanation: Changes in non-reproductive tissues cannot be passed on the the DNA of the germ cells. The traits developed during the lifetime of an individual that cannot be passed on to its progenies are acquired traits.

Question.27.
Assertion : Chromosomes are known as hereditary vehicles.
Reason : The chromosomes are capable of self reproduction and maintaining morphological and physiological properties through successive generations.

(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).

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