Class 10 Science Chapter 8 Practice Question Answers - Heredity and Evolution

Fill in the Blanks
Q1: The basic unit of heredity is called a _______.
Ans: gene

Q2: The process by which favorable traits are passed on to the next generation is called _______.
Ans: natural selection

Q3: The scientific study of heredity and variation is known as _______.
Ans: genetics

Q4: The sex determination in humans is based on the presence of _______ chromosome in the individual.
Ans: Y

Q5: The first filial generation obtained in a cross is represented as _______.
Ans: F1

Short Answer Questions
Q6: What is meant by the term "variation" in the context of heredity and evolution?
Ans: Variation refers to the differences that exist between individuals of the same species. It is caused by genetic factors and environmental influences, contributing to the diversity of traits within a population.

Q7: Define Mendel's Law of Segregation.
Ans: Mendel's Law of Segregation states that during gamete formation, the alleles (alternate forms of a gene) segregate from each other, so that each gamete carries only one allele for a particular trait.

Q8: How does a new species arise according to Darwin's theory of natural selection
Ans: According to Darwin's theory, a new species arises through the process of natural selection. Individuals with favorable traits that enhance survival and reproduction have a better chance of passing on their genes to the next generation. Over time, these accumulated changes can lead to the development of a new species.

Q9: Differentiate between homologous and analogous structures.
Ans: Homologous structures are similar in structure but may have different functions, indicating a common evolutionary origin (e.g., the bones in the forelimbs of mammals). Analogous structures have similar functions but different structures, arising from different evolutionary paths (e.g., wings of birds and insects).

Q10: How is the sex of a newborn determined in humans?
Ans: In humans, the sex of a newborn is determined by the combination of sex chromosomes inherited from the parents. If the child inherits an X chromosome from both parents, the child will be female (XX). If the child inherits an X chromosome from the mother and a Y chromosome from the father, the child will be male (XY).

Long Answer Questions
Q11: Describe the process of sexual reproduction in flowering plants.
Ans: In flowering plants, sexual reproduction involves the formation of male and female gametes. Pollination transfers pollen grains from the anther to the stigma. The pollen tube grows through the style to reach the ovary. Fertilization occurs when the male gamete fuses with the female gamete (ovule), leading to the formation of a zygote. The zygote develops into an embryo, and the ovule develops into a seed. Eventually, the seed germinates to form a new plant.

Q12: Explain the inheritance of traits with the help of a Punnett square.
Ans: A Punnett square is a tool used to predict the possible outcomes of a genetic cross. It shows the different combinations of alleles that can result from the mating of two individuals. Each parent's alleles are written along the top and side of the square. The boxes inside the square represent the possible genotypes of the offspring. By combining the alleles from each parent, the potential genotypes and phenotypes of the offspring can be determined.

Q13: How do fossils provide evidence for evolution? Give an example.
Ans: Fossils are preserved remains or traces of organisms from the past. They provide a record of the history of life on Earth and show how organisms have changed over time. For example, the fossil record of horses demonstrates the evolution of their limb structure from small, multi-toed ancestors to the single-toed modern horses, reflecting an adaptive response to changing environments.

Q14: Discuss Lamarck's theory of evolution and its shortcomings.
Ans: Lamarck's theory of evolution proposed that organisms could acquire or lose traits during their lifetimes in response to environmental changes and pass these changes to their offspring. However, Lamarck's theory lacks a mechanism of inheritance (like genes), and acquired traits do not actually get passed on in the manner he suggested. Modern genetics and the discovery of DNA have shown that traits are primarily inherited through genes, not acquired during an organism's lifetime.

Q15: How does natural selection lead to the development of antibiotic-resistant bacteria?
Ans: Natural selection operates in bacterial populations when antibiotics are used. Some bacteria may have mutations that make them resistant to antibiotics. When antibiotics are applied, susceptible bacteria die off, but the resistant ones survive and reproduce. Over time, the resistant bacteria become more prevalent, leading to the evolution of antibiotic-resistant strains. This is a classic example of natural selection in action.