HEREDITY AND EVOLUTION
EXTRA IMPORTANT QUESTIONS WITH ANSWERS :
1.Which of the processes, sexual reproduction or asexual reproduction, brings about
maximum variations in the offsprings ?
Answer : Sexual Reproduction
2. Name one variation in humans connected with ears.
Answer: Free Earlobes.
3. What constitutes the link between one generation and the next ?
Answer: Gametes.
4. If the trait A exists in 10% of a population of an asexually reproducing species and a
trait B exists in 60% of the same population, which trait is likely to have arisen earlier ?
Answer: B.
5. Mendel said that the characteristics or traits of organisms are carried from one
generation to the next by internal factors which occur in pairs. What is the modern
name for these factors ?
Answer: Genes.
6. Some plants occur in one of the two sizes : tall or dwarf. This characteristic is
controlled by one pair of genes. Tallness is dominant to dwarfness. Choose suitable
letters for this gene pair.
Answer: Tt.
7. What are the chromosomes XY and XX known as ?
Answer: Sex Chromosomes.
8. Which of the two, sperm or ovum, decides the sex of the child ?
Answer: Sperm.
9. A new born child has an XY pair of chromosomes. Will it be a baby boy or a baby
girl ?
Answer: Baby boy
10. Which of the following combinations of sex chromosomes produce a male child : XX
or XY ?
Answer: XY.
10. Name the first scientist who studied the inheritance of traits from one generation to
the next.
Answer : Gregor Mendel
11. What type of plants were used by Mendel for conducting his experiments on
inheritance ?
Answer : Pea plants.
12. The gene for red hair is recessive to the gene for black hair. What will be the hair
colour of a person if he inherits a gene for red hair from his mother and a gene for
black hair from his father ?
Answer : Black hair.
, 13. What are the four blood groups in humans ?
Answer : A, B, AB and O.
14. Name one reptile in each case where higher incubation temperature leads to the
development of : (a) male progeny, (b) female progeny.
Answer :
(a) Lizard
(b) Turtle
15. Fill in the following blanks with suitable words :Fill in the following blanks with
suitable words :
(a) Genes always work in Pairs
(b) In pea plants, the gene for dwarfness is Recessive whereas that for tallness is Dominant
(c) Most people have Free earlobes but some have attached earlobes.
(d) A human gamete contains 23 chromosomes whereas a normal body cell has 46
chromosomes in it.
(e) All races of man have four blood groups.
(f) The sex chromosomes for a female are XX whereas that for a male are XY.
16. Which of the following represent tall plants and which represent short plants (or
dwarf plants) ?Which of the following represent tall plants and which represent short
plants (or dwarf plants) ?
(a) Tt
(b) tt
(c) TT
Give reason for your choice (The symbols have their usual meaning).
Answer :
(a) Tall – Tt will have tall plants because of the presence of T which is dominant gene and t is
recessive gene.
(b) Dwarf plants: It is dwarf due to the presence of both the recessive genes.
(c) Tall plants: These plants are tall due to the presence of both the dominant genes.
17. A man having blood group O marries a woman having blood group B and they have
a daughter. What will be the blood group of the daughter ?
Answer : Equal chance of having blood group O or blood group B.
18. Name an animal in which individuals can change sex. What does this indicate ?
Answer : Snails: This indicates that sex is not determined genetically in some animals.
19. Explain with an example, how genes control the characteristics (or traits).
Answer : The characteristics or traits in animals and plants are controlled by genes. For
example the transmission of colour of hair from the parents to the child. If a mother has black
hair and the father has blonde hair and the child has black hair then the transmission of genes
for hair colour from the mother and father to the child is as follows: Mother’s cell contains two
genes HH for black hair. Both the genes HH are dominant genes, so the mother has black
hair. Father’s cell contains two genes (hh) for blonde hair. The two genes hh are recessive
genes, so the father has blonde hair. Now, during the process of reproduction, the mother
transmits one of the dominant genes H for black hair to the child and the father transmits one
EXTRA IMPORTANT QUESTIONS WITH ANSWERS :
1.Which of the processes, sexual reproduction or asexual reproduction, brings about
maximum variations in the offsprings ?
Answer : Sexual Reproduction
2. Name one variation in humans connected with ears.
Answer: Free Earlobes.
3. What constitutes the link between one generation and the next ?
Answer: Gametes.
4. If the trait A exists in 10% of a population of an asexually reproducing species and a
trait B exists in 60% of the same population, which trait is likely to have arisen earlier ?
Answer: B.
5. Mendel said that the characteristics or traits of organisms are carried from one
generation to the next by internal factors which occur in pairs. What is the modern
name for these factors ?
Answer: Genes.
6. Some plants occur in one of the two sizes : tall or dwarf. This characteristic is
controlled by one pair of genes. Tallness is dominant to dwarfness. Choose suitable
letters for this gene pair.
Answer: Tt.
7. What are the chromosomes XY and XX known as ?
Answer: Sex Chromosomes.
8. Which of the two, sperm or ovum, decides the sex of the child ?
Answer: Sperm.
9. A new born child has an XY pair of chromosomes. Will it be a baby boy or a baby
girl ?
Answer: Baby boy
10. Which of the following combinations of sex chromosomes produce a male child : XX
or XY ?
Answer: XY.
10. Name the first scientist who studied the inheritance of traits from one generation to
the next.
Answer : Gregor Mendel
11. What type of plants were used by Mendel for conducting his experiments on
inheritance ?
Answer : Pea plants.
12. The gene for red hair is recessive to the gene for black hair. What will be the hair
colour of a person if he inherits a gene for red hair from his mother and a gene for
black hair from his father ?
Answer : Black hair.
, 13. What are the four blood groups in humans ?
Answer : A, B, AB and O.
14. Name one reptile in each case where higher incubation temperature leads to the
development of : (a) male progeny, (b) female progeny.
Answer :
(a) Lizard
(b) Turtle
15. Fill in the following blanks with suitable words :Fill in the following blanks with
suitable words :
(a) Genes always work in Pairs
(b) In pea plants, the gene for dwarfness is Recessive whereas that for tallness is Dominant
(c) Most people have Free earlobes but some have attached earlobes.
(d) A human gamete contains 23 chromosomes whereas a normal body cell has 46
chromosomes in it.
(e) All races of man have four blood groups.
(f) The sex chromosomes for a female are XX whereas that for a male are XY.
16. Which of the following represent tall plants and which represent short plants (or
dwarf plants) ?Which of the following represent tall plants and which represent short
plants (or dwarf plants) ?
(a) Tt
(b) tt
(c) TT
Give reason for your choice (The symbols have their usual meaning).
Answer :
(a) Tall – Tt will have tall plants because of the presence of T which is dominant gene and t is
recessive gene.
(b) Dwarf plants: It is dwarf due to the presence of both the recessive genes.
(c) Tall plants: These plants are tall due to the presence of both the dominant genes.
17. A man having blood group O marries a woman having blood group B and they have
a daughter. What will be the blood group of the daughter ?
Answer : Equal chance of having blood group O or blood group B.
18. Name an animal in which individuals can change sex. What does this indicate ?
Answer : Snails: This indicates that sex is not determined genetically in some animals.
19. Explain with an example, how genes control the characteristics (or traits).
Answer : The characteristics or traits in animals and plants are controlled by genes. For
example the transmission of colour of hair from the parents to the child. If a mother has black
hair and the father has blonde hair and the child has black hair then the transmission of genes
for hair colour from the mother and father to the child is as follows: Mother’s cell contains two
genes HH for black hair. Both the genes HH are dominant genes, so the mother has black
hair. Father’s cell contains two genes (hh) for blonde hair. The two genes hh are recessive
genes, so the father has blonde hair. Now, during the process of reproduction, the mother
transmits one of the dominant genes H for black hair to the child and the father transmits one
