Class 10 Science Chapter 8 Heredity
Class 10 Science Chapter 8 Heredity
NCERT Solution Class 10 Science Chapter 8 Heredity
Page No. 129 || Class 10 Science Chapter 8 Heredity
Question 1
If a 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
- Trait B is likely to have arisen earlier.
- Trait A: Its present in 10% population i.e., present in less population. It must have been in existence for less time (recent trait) and hence it must be a new trait.
- Trait B: Its present in 60% population i.e., present in more populations. It must have been in existence for more time (earlier trait) and hence it must be a old trait.
Science Chapter 8 Heredity
Question 2
How does the creation of variations in a species promote survival?
Answer
The creation of variations in a species promotes survival with the help of the following example:
- If there were a population of bacteria living in temperate waters, and if the water temperature were to be increased by global warming, most of these bacteria would die, but the few variants resistant to heat would survive and grow further.
- Variation is thus useful for the survival of species over time.
Class 10 Science Chapter 8 Heredity
Page No. 133 || Class 10 Science Chapter 8 Heredity
Question 1
How do Mendel’s experiments show that traits may be dominant or recessive?
Answer
In Monohybrid cross of Mendel between tall and dwarf pea plant, all progeny in F1 generation are tall and in F2 generation, 75% of pea plants are tall but 25% are dwarf. This shows that traits are dominant or recessive.
Question 2
How do Mendel’s experiments show that traits are inherited independently?
Answer
When a pea plant having round green seeds is crossed with a pea plant having wrinkled yellow seeds in F1 generation all the plants have round yellow seeds. But in F2 generation two new traits that is round yellow and wrinkled green appear. This shows that traits are inherited independently.
Question 3
A man with blood group A marries a woman with blood group O and 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?
Answer
No. This information is not sufficient to determine which of the traits – blood group A or O – is dominant. This is because we do not know about the blood group of all the progeny.
Blood group A can be genotypically AA or AO. Hence, the information is incomplete to draw any such conclusion.
Question 4
How is the sex of the child determined in human beings?
Answer
The sex of a child is determined by the combination of sex chromosomes inherited from both parents. Here’s how it works:
- Sex Chromosomes: Humans have two types of sex chromosomes: X and Y. Females have two X chromosomes (XX), while males have one X and one Y chromosome (XY).
- Parental Contribution: Each parent contributes one sex chromosome to their child. The mother always provides an X chromosome (since she has XX), and the father provides either an X or a Y chromosome (since he has XY).
- Determining the Sex:
- If the father contributes an X chromosome: The child will have two X chromosomes (XX), which means the child will be female.
- If the father contributes a Y chromosome: The child will have one X and one Y chromosome (XY), which means the child will be male.
Class 10 Science Chapter 8 Heredity
Exercise Page No. 133 ||Class 10 Science Chapter 8 Heredity
Question 1
A 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
Answer
(c) TtWW
Question 2
A study found that children with light-coloured eyes are likely to have parents with light-coloured eyes. On this basis, can we say anything about whether the light eye colour trait is dominant or recessive? Why or why not?
Answer
This information is not sufficient. For considering a trait as dominant or recessive, we need data of at least three generations. This data is about only two generations.
Question 3
Outline a project which aims to find the dominant coat colour in dogs.
Answer
Suppose a black homozygous male is mated with a white homozygous female. If the progeny has all black dogs then the dominant coat colour is black.
Question 4
How is the equal genetic contribution of male and female parents ensured in the progeny?
Answer
The genetic material in most organisms is present in pairs of chromosomes. Gametes in sexually reproducing organisms are formed by the process of meiosis during which half of the genetic material goes into each gamete. When the gametes from male and female parents fuse with each other during sexual reproduction, the normal complement is restored. Half of the genetic material comes from the female and half from the male.
Read Also: Important Questions of Class 10 Science Heredity
Pingback: NCERT Solutions For Class 10 Science