8. Heredity Class 10 Science Solutions English Medium-Long Additional Questions With Solutions

NCERT Solutions Class 10 Science English Medium

8. Heredity

Topic: Long Additional Questions With Solutions

Long Additional Questions with Solutions – Chapter 8: Heredity

Q1: What is heredity? Explain the importance of heredity and variation in living organisms.

Ans: Heredity is the process by which characteristics are passed from parents to their offspring through genes. Genes are present on chromosomes and carry hereditary information from one generation to the next.

Variation refers to the differences in characteristics among individuals of the same species.

Importance of Heredity and Variation:

• Heredity helps maintain the continuity of species.
• Variation enables organisms to adapt to changing environmental conditions.
• Useful variations improve the chances of survival.
• Variation forms the basis of evolution.
• It helps species survive natural disasters and diseases.

Q2: Explain Mendel's monohybrid cross with the help of an example.

Ans: A monohybrid cross is a cross between two parents differing in one pair of contrasting characters.

Mendel crossed a pure tall pea plant (TT) with a pure dwarf pea plant (tt).

F₁ Generation:

• TT × tt
• All offspring were Tt (Tall).

F₂ Generation:

• Tt × Tt
• Phenotypic Ratio = 3 Tall : 1 Dwarf
• Genotypic Ratio = 1 TT : 2 Tt : 1 tt

This experiment led Mendel to propose the Law of Dominance and the Law of Segregation.

Q3: State and explain Mendel's three laws of inheritance.

Ans:

1. Law of Dominance

When two contrasting traits are present together, only the dominant trait is expressed in the offspring.

2. Law of Segregation

The two alleles of a gene separate during gamete formation, and each gamete receives only one allele.

3. Law of Independent Assortment

Different pairs of alleles are inherited independently of one another during gamete formation.

These laws explain how traits are inherited from one generation to another.

Q4: Differentiate between inherited traits and acquired traits with suitable examples.

Ans:

Q5: Explain the mechanism of sex determination in human beings.

Ans:

Human beings have 46 chromosomes, including one pair of sex chromosomes.

• Female: XX
• Male: XY

The mother always contributes an X chromosome through the egg.

The father produces two types of sperms:

• X-bearing sperm
• Y-bearing sperm

If an X-bearing sperm fertilizes the egg, the child will be XX (Girl).

If a Y-bearing sperm fertilizes the egg, the child will be XY (Boy).

Therefore, the father is responsible for determining the sex of the child.

Q6: Explain the relationship between heredity and evolution.

Ans:

Heredity transfers genetic information from parents to offspring. During reproduction, small variations arise due to genetic recombination and mutations.

Some variations help organisms survive better in changing environments. These useful variations are inherited by future generations.

Over many generations, the accumulation of such favorable variations results in evolution.

Thus, heredity provides continuity, while variation drives evolution.

Q7: Why did Gregor Mendel choose pea plants for his experiments? Explain.

Ans:

Mendel selected pea plants because they possessed several useful characteristics.

• They had many clearly distinguishable contrasting traits.
• They had a short life cycle.
• They produced a large number of offspring.
• They naturally self-pollinated but could also be cross-pollinated easily.
• Pure breeding varieties were easily available.

These features made pea plants ideal for studying inheritance.

Q8: Explain the significance of variation in the process of evolution.

Ans:

Variation is essential for the survival and evolution of species.

• It helps organisms adapt to changing environmental conditions.
• Useful variations increase survival and reproductive success.
• Natural selection favors beneficial variations.
• Over generations, these variations accumulate and lead to the formation of new species.
• Without variation, evolution would not occur.

Q9: Describe the structure and function of genes, chromosomes, and DNA.

Ans:

• DNA (Deoxyribonucleic Acid): The hereditary material that stores genetic information.
• Gene: A small segment of DNA that controls a specific inherited trait.
• Chromosome: A thread-like structure made of DNA and proteins that carries thousands of genes.

Genes present on chromosomes carry hereditary information from parents to offspring.

Q10: Explain how Mendel's experiments laid the foundation of modern genetics.

Ans:

Gregor Mendel is known as the Father of Genetics because his experiments on pea plants explained the basic principles of inheritance.

• He proved that traits are controlled by factors (now called genes).
• He introduced the concepts of dominant and recessive traits.
• He explained how traits are transmitted from one generation to the next.
• He proposed the Laws of Dominance, Segregation, and Independent Assortment.
• His discoveries became the foundation of modern genetics and heredity.

Large question with answer

Q1. 'Different species use different strategies to determine sex of a newborn individual. It can be environmental cues or genetically determined'. Explain the statement by giving example for each. 

Answer: Different species use very different strategies for this. Some rely entirely on environmental cues. Thus, in some animals, the temperature at which fertilised eggs are kept determines whether the animals developing in the eggs will be male or female. In other animals, such as snails, individuals can change sex, indicating that sex is not genetically determined. However, in human beings, the sex of the individual is largely genetically determined. In other words, the genes inherited from our parents decide whether we will be boys or girls.

Q2. 

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