ROUTERA

Heredity and Evolution

Class 10th Science Chapter Assertion and Reason

Heredity and Evolution

  • Options:
    a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
    b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
    c) Assertion (A) is true, but Reason (R) is false.
    d) Assertion (A) is false, but Reason (R) is true.

Question 1

Assertion (A): Traits are inherited from parents to offspring.
Reason (R): Genes are the units of heredity that determine traits.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: Genes carry the genetic information from parents to offspring, and they are responsible for the physical and behavioral traits of an organism.

Question 2

Assertion (A): A hybrid organism has two different alleles for a trait.
Reason (R): A hybrid organism is produced from the cross of two purebred organisms.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: A hybrid organism results from the mating of two purebred organisms with different traits, resulting in a combination of alleles.

Question 3

Assertion (A): Incomplete dominance results in a blending of traits in offspring.
Reason (R): In incomplete dominance, neither allele is completely dominant over the other.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: Incomplete dominance occurs when the heterozygous phenotype is a blend of the two homozygous phenotypes, demonstrating a mix of traits.

Question 4

Assertion (A): Evolution is the change in the heritable characteristics of biological populations over successive generations.
Reason (R): Natural selection is the mechanism that drives evolution.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: Evolution occurs as a result of natural selection, where organisms with favorable traits are more likely to survive and reproduce.

Question 5

Assertion (A): Chromosomes are made up of DNA and proteins.
Reason (R): DNA contains the genetic code that determines an organism’s traits.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: Chromosomes are the structures that house DNA; the genetic code in DNA directs the development of traits in an organism.

Question 6

Assertion (A): The theory of evolution was proposed by Charles Darwin.
Reason (R): Darwin introduced the concept of "survival of the fittest."

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: Charles Darwin's theory of evolution emphasized natural selection, which is often summarized by the phrase "survival of the fittest."

Question 7

Assertion (A): Mendel's laws of inheritance are based on his experiments with pea plants.
Reason (R): Mendel's experiments established the foundation for understanding dominant and recessive traits.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: Mendel's systematic breeding experiments with pea plants led to the formulation of his laws of inheritance, explaining how traits are passed from one generation to the next.

Question 8

Assertion (A): A phenotype is the physical expression of a genotype.
Reason (R): The genotype is the genetic makeup of an organism.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: The phenotype is influenced by the genotype; it reflects how genetic information is expressed in observable traits.

Question 9

Assertion (A): Mutations can introduce new traits into a population.
Reason (R): Mutations are random changes in the DNA sequence.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: Mutations can result in new genetic variations, providing raw material for evolution and potentially introducing new traits to a population.

Question 10

Assertion (A): The fossil record provides evidence for evolution.
Reason (R): Fossils show the physical characteristics of organisms that lived in the past.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: The fossil record reveals changes in organisms over time, demonstrating how species have evolved and adapted to their environments.

Question 11

Assertion (A): Genetic variation is essential for the process of natural selection.
Reason (R): Natural selection can only act on traits that vary among individuals in a population.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: Natural selection relies on genetic variation to favor individuals with advantageous traits, which leads to the evolution of populations.

Question 12

Assertion (A): All living organisms share a common genetic code.
Reason (R): The universal genetic code supports the idea of common ancestry among diverse species.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: The fact that all organisms use the same genetic code for protein synthesis suggests that they share a common evolutionary ancestor.

Question 13

Assertion (A): Sex-linked traits are often expressed differently in males and females.
Reason (R): Males have only one X chromosome, while females have two.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: Because males have only one X chromosome, they are more likely to express recessive traits linked to that chromosome compared to females who have two X chromosomes.

Question 14

Assertion (A): Artificial selection is a form of selective breeding.
Reason (R): In artificial selection, humans choose specific traits they want to propagate in a population.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: Artificial selection involves human intervention to breed plants and animals for desired characteristics, illustrating human influence on evolution.

Question 15

Assertion (A): The study of embryology provides insights into evolutionary relationships.
Reason (R): Similarities in embryonic development suggest common ancestry among species.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: Comparative embryology reveals that many organisms share similar developmental stages, indicating a shared evolutionary background.

Question 16

Assertion (A): Chromosomal abnormalities can lead to genetic disorders.
Reason (R): Abnormalities may result from errors during cell division.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: Errors in meiosis or mitosis can lead to conditions such as Down syndrome, which arise from an abnormal number of chromosomes.

Question 17

Assertion (A): Species that are closely related have more similar DNA sequences.
Reason (R): DNA sequences change over time due to mutations and evolutionary pressures.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: Similar DNA sequences indicate recent common ancestry, while differences reflect evolutionary divergence over time.

Question 18

Assertion (A): The law of segregation states that alleles segregate during gamete formation.
Reason (R): Each gamete carries only one allele for each gene.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: According to Mendel's law of segregation, during gamete formation, the two alleles for each trait separate, ensuring that each gamete receives only one allele.

Question 19

Assertion (A): Genetic drift can lead to changes in allele frequencies in a population.
Reason (R): Genetic drift occurs due to random sampling of alleles.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: Genetic drift is a random process that can lead to changes in allele frequencies over generations, particularly in small populations.

Question 20

Assertion (A): Speciation occurs when a population becomes reproductively isolated.
Reason (R): Reproductive isolation prevents gene flow between populations.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: When populations are reproductively isolated, they can evolve independently, leading to the formation of new species.