NCERT Solutions For Class 10 Biology Chapter 8 Heredity: Download PDF for Free

NCERT Solutions for Class 10 Heredity: NCERT books are considered the best source for preparation of theoretical concepts and making the basics strong. The questions provided in NCERT textbooks at the end of each chapter and intext question are quite important for examination point of view and for better understanding of the concepts. It is highly recommended to follow the NCERT Textbook for the exam. 

In this article you will find all the NCERT intext and final exercise solutions for CBSE Class 10 Science Chapter 8, Heredity. All the class 10 Science NCERT solutions have been collated in PDF format which students may easily download free of cost. 

Check NCERT Solutions for CBSE Class 10  Science Biology Chapter 8 Heredity: 

Intext Solutions Page No. -129

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?

Solution : In asexually reproducing species, traits are passed down directly from parent to offspring, and changes in traits can accumulate over time.

If trait A exists in 10% of the population and trait B exists in 60% of the population, it’s likely that trait B arose earlier. Here’s why:

1. Higher Frequency: Trait B is found in a larger percentage of the population (60%), which suggests it has been around for a longer time and has had more opportunities to spread through the population.
2. Spread Over Time: Since trait B is more common, it means it was probably established in the population before trait A and has had more time to be passed on to many individuals.

Question 2:  How does the creation of variations in a species promote survival?

Solution : Creating variations in a species helps promote survival in several ways:

1. Adaptation: Variations mean that some individuals have traits better suited to their environment. For example, if a certain variation allows an animal to find food more easily, those individuals are more likely to survive and reproduce.
2. Disease Resistance: Variations can include different levels of resistance to diseases. If some individuals have traits that make them resistant to a disease, they can survive and pass on those traits, helping the species survive outbreaks.
3. Environmental Changes: Variations help a species adapt to changes in the environment. If the environment changes, individuals with beneficial traits are more likely to thrive, while others may not.
4. Diverse Traits: Having a variety of traits in a population means that some individuals will always have traits that are useful, no matter what challenges arise.

Intext Solutions Page No. - 133

Question 1: How do Mendel’s experiments show that traits may be dominant or recessive? 

Solution : Mendel's experiments with pea plants demonstrated that traits can be either dominant or recessive through his systematic breeding and observation. Here’s how his experiments showed this:

1. Crossing Plants with Different Traits: Mendel cross-bred pea plants with different traits, such as tall and short plants. He observed the traits in the offspring (F1 generation) and found that only one trait appeared, while the other was hidden.
2. Dominant Traits: In the F1 generation, Mendel found that the trait which appeared was called the dominant trait. For example, if tall plants were crossed with short plants, all the F1 offspring were tall. The tall trait "dominated" over the short trait.
3. Recessive Traits: The trait that did not appear in the F1 generation was called the recessive trait. The short trait was hidden but did not disappear. When Mendel let the F1 generation self-pollinate, the recessive trait reappeared in the F2 generation, showing that it was still present but masked in the F1 generation.
4. Ratios in the F2 Generation: Mendel’s detailed observations of the F2 generation showed a consistent ratio of dominant to recessive traits (approximately 3:1). This ratio further confirmed that dominant traits mask the presence of recessive traits.

Question 2: How do Mendel’s experiments show that traits are inherited independently? 

Solution : Mendel’s experiments showed that traits are inherited independently through these simple steps:

1. Crossing Different Traits: Mendel crossed pea plants with two different traits, like tall vs. short and purple vs. white flowers.
2. Observing Offspring: In the first generation of offspring (F1), all plants showed the dominant traits, but Mendel couldn’t see the mix of traits yet.
3. Checking the Next Generation: When Mendel looked at the next generation (F2), he saw all possible combinations of the traits, like tall purple, tall white, short purple, and short white plants.
4. Finding Patterns: The traits appeared in a specific ratio, showing that each trait was passed on independently of the other traits.

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? 

Solution : Yes, this information is enough to determine that blood group A is dominant and blood group O is recessive. Here’s why:

1. Blood Group Basics: Blood group A is dominant, while blood group O is recessive. This means that if you have an A allele, it will show up in your blood group, even if you have one O allele.
2. Man’s Genotype: The man with blood group A must have one A allele and one O allele (AO) because he has a daughter with blood group O. He can’t have two A alleles (AA) because then he wouldn’t have an O allele to pass on.
3. Woman’s Genotype: The woman with blood group O has two O alleles (OO) because O is recessive.
4. Daughter’s Blood Group: For the daughter to have blood group O, she needs to get an O allele from both parents. Since the daughter has blood group O, it proves that the man must have the O allele, confirming that A is dominant.

Question 4: How is the sex of the child determined in human beings?

Solution : The sex of a child is determined by the combination of sex chromosomes inherited from both parents. Here’s how it works:

1. 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).
2. 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).
3. 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.

EXERCISE

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

Solution : 

(d) 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?

Solution : Yes, we can say that light eye color is likely a recessive trait based on the observation that children with light-colored eyes often have parents with light-colored eyes. Here’s why:

1. Recessive Traits: For a child to have light-colored eyes, both parents need to pass on a recessive gene for light eye color.
2. Dominant Traits: If light eye color were a dominant trait, children could have light-colored eyes even if only one parent had them, because dominant traits can show up with just one copy.
3. Observation: Since children with light-colored eyes usually have both parents with light-colored eyes, it suggests that light eye color is recessive. Both parents need to have or carry the recessive gene for their child to have light-colored eyes.

Question 4: How is the equal genetic contribution of male and female parents ensured in the progeny?

Solution : Equal genetic contribution from both parents is ensured through the following steps:

1. Gametes: Each parent produces special cells called gametes (sperm from the father and eggs from the mother), each containing half of their genetic material.
2. Fertilization: When a sperm cell from the father meets an egg cell from the mother, they combine to form a new cell (the zygote) with a complete set of genes—half from the mother and half from the father.
3. Genetic Material: This combination means that the offspring get equal genetic input from both parents, with one set of chromosomes coming from each.

To download these solutions in PDF format, click on the link below:

Download NCERT Class 10 Science Chapter 8 Heredity Solution Manual PDF

These solutions follows the latest CBSE Class 10 Science syllabus 2024-25 and the updates NCERT textbook thus, do not include the deleted topics.

Check:

• CBSE Class 10 Mock Test Videos For Quick Revision
• CBSE Class 10 Science Lab Manual PDF

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