CBSE Class 10 Biology Heredity And Evolution Worksheet Set D

Objective Questions

Case Study Question

In some animals, the temperature at which fertilised eggs are kept determines whether the animal developing in the egg will be male or female. In other animals, such as snails, individuals can change sex, that is sex is not genetically determined. In human beings, sex of individuals is largely genetically determined. All chromosomes in human beings are not paired. We have 22 pairs and one pair of sex chromosomes which is odd and not always a perfect pair.

Question : Which pair of chromosomes are present in Male
(a) XX
(b) YY
(c) XY
(d) XXY
Answer : C

Question : How many pairs of chromosomes are called autosomes?
(a) 23
(b) 22
(c) 21
(d) 20
Answer : B

Question : Who is responsible for birth of male child?
(a) Father
(b) Mother
(c) Father only in first pregnancy.
(d) Mother only in first pregnancy
Answer : A

Question : Which pair of chromosomes are present in female?
(a) XX
(b) YY
(c) XY
(d) XXY
Answer : A

Question : Which of the following statement is true?
(a) Men have short sized X chromosome
(b) Men have one long sized Y chromosome
(c) Men have normal sized Y chromosome
(d) Men have one short sized Y chromosome
Answer : D

Very Short Answer Questions

Question : Define speciation.
Answer : Speciation means origin of new species from the existing one.

Question : How are characters or traits controlled?
Answer : Characters or traits of an organism are controlled by the genes /DNA.

Question : In a beetle population, the number of green beetles is more than blue and red beetles. Give a reason behind this situation.
Answer :  Variation/Natural selection.

Question : What is genetic drift?
Answer :  The change in the frequency of certain genes in a population over generations.

Question : What is heredity?
Answer : Transmission of characters and traits from one generation to the next.

Question : How many pairs of chromosomes are present in human beings?
Answer :  23 pairs.

Question : Name the term used for the traits that are exhibited externally.
Answer : Phenotype.

Question : An organism which is a worm, has very simple ‘eyes’, that are really eye spots which detect light. Name that organism.
Answer :  Planaria.

Question : Why is the progeny always tall when a tall pea plant is crossed with a short pea plant?
Answer : The trait which represents the tallness in a pea plant is dominant over the another trait, shortness (dwarf).

Question : Human have evolved from chimpanzee. Is it true? 
Answer :  No, the two species have evolved in separate ways from a common ancestor.

Question : Why is it that asexual reproduction produces exact copies but sometimes minor variations are also seen in next progeny?
Answer :  Since no biochemical reaction is reliable, therefore, in copying of DNA, it may cause slight difference which causes these variations.

Question : How can the chromosomes be identified?
Answer :  In human beings, the individual chromosomes are identified by their lengths, position of centromere and banding pattern on staining.

Question : No two individuals are absolutely alike in a population. Why?
Answer :  All individuals have different kind of DNA. So all individuals are not alike to each other.

Question : What is a gene?
Answer :  It is a functional piece of DNA that is responsible for expression of a trait in the organisms.

Question : What indication do we get by reappearance of dwarf plant in F₂ generation?
Answer :  After obtaining progeny in F₂ generation in a dihybrid cross, Mendel concluded that when two pairs of traits are combined in a hybrid, one pair of character segregates independently of the other pair of character.

Question : Mendel observed a contrasting trait in relation to position of flowers. Mention the trait.
Answer : Axial flower position (dominant), terminal flower position (recessive).

Question : Write the sex of the baby that inherits Y-chromosomes from the father.
Answer :   Male.

Question : What is the phenotypic ratio of a dihybrid cross in F₂ generation?
Answer :  9 : 3 : 3 : 1.

Question : What is the effect of DNA copying which is not perfectly accurate on the reproduction process?
Answer :  It will result in less variations which may further lead to less adaptation to changing environment, thus, giving less chances of survival.

Question : What are the basic events in evolution?
Answer :  The changes in DNA during reproduction are the basic events in evolution.