Kerala SSLC · Biology · Class 10

Genetics and Evolution: Important Questions with Answers

These are 10 important multiple-choice questions from the Kerala SSLC Biology chapter “Genetics and Evolution” (Kerala SCERT syllabus). Each one shows the correct answer and a short explanation of why it is right. Try answering before you read the answer. ExamSummary has 10 practice questions on this chapter in total.

  1. Q1.In Mendel's experiment with pea plants, what is the phenotypic ratio observed in the F2 generation of a monohybrid cross between pure tall and pure dwarf plants?

    • A)1:1
    • B)3:1
    • C)9:3:3:1
    • D)1:2:1

    Answer: B) 3:1

    Mendel's law of segregation states that alleles separate during gamete formation. In the F2 generation of a monohybrid cross, the dominant trait appears three times for every one recessive trait.

  2. Q2.Which combination of sex chromosomes determines the male sex in humans according to the principles taught in the Kerala SSLC biology curriculum?

    • A)XX
    • B)YY
    • C)XY
    • D)X0

    Answer: C) XY

    Humans have 23 pairs of chromosomes, with the 23rd pair being the sex chromosomes. Males possess one X and one Y chromosome (XY), while females possess two X chromosomes (XX).

  3. Q3.Where are fossils typically found, providing evidence for the history of life on Earth?

    • A)Igneous rocks
    • B)Sedimentary rocks
    • C)Metamorphic rocks
    • D)Volcanic ash

    Answer: B) Sedimentary rocks

    Fossils are preserved remains of ancient organisms found primarily in sedimentary rocks. These layers of rock form over time by depositing sediments, trapping organic remains before they decay.

  4. Q4.What distinguishes homologous organs from analogous organs in the context of evolution?

    • A)Same origin/different function
    • B)Different origin/same function
    • C)Same origin/same function
    • D)Different origin/different function

    Answer: A) Same origin/different function

    Homologous organs share a common ancestral origin but may perform different functions due to divergent evolution. Analogous organs, conversely, have different origins but perform similar functions due to convergent evolution.

  5. Q5.Which nitrogenous base is present in RNA but absent in DNA?

    • A)Adenine
    • B)Guanine
    • C)Uracil
    • D)Thymine

    Answer: C) Uracil

    DNA contains the bases Adenine, Guanine, Cytosine, and Thymine. RNA replaces Thymine with Uracil, which pairs with Adenine during protein synthesis processes.

  6. Q6.Why does sexual reproduction result in greater genetic variation compared to asexual reproduction?

    • A)It involves only mitosis
    • B)It involves fusion of gametes with unique gene combinations
    • C)It occurs faster than asexual reproduction
    • D)It produces clones of the parent

    Answer: B) It involves fusion of gametes with unique gene combinations

    Sexual reproduction involves meiosis and fertilization, shuffling genes from two parents. This mixing creates new combinations of traits, increasing variation within the population.

  7. Q7.According to modern genetics, why are acquired traits (like muscle growth from exercise) not passed on to offspring?

    • A)They occur only in males
    • B)They do not alter the DNA in germ cells
    • C)They are always recessive
    • D)They disappear after one generation naturally

    Answer: B) They do not alter the DNA in germ cells

    Acquired traits affect somatic cells (body cells) and do not change the genetic material in reproductive cells (germ cells). Therefore, these changes cannot be transmitted to the next generation through DNA.

  8. Q8.If a couple has already had three sons, what is the probability that their fourth child will be a girl?

    • A)0%
    • B)25%
    • C)50%
    • D)75%

    Answer: C) 50%

    The sex of each child is determined independently by the sperm carrying either an X or a Y chromosome. Past births do not influence the probability of future births, which remains 50% for either sex.

  9. Q9.Which of the following is considered a vestigial organ in humans, suggesting evolutionary history?

    • A)Heart
    • B)Appendix
    • C)Liver
    • D)Kidney

    Answer: B) Appendix

    Vestigial organs are remnants of structures that were functional in ancestors but have lost most or all of their original function. The human appendix is a classic example cited in the syllabus as a vestigial structure.

  10. Q10.What is the primary mechanism proposed by Charles Darwin for how species evolve over time?

    • A)Use and disuse of organs
    • B)Natural selection
    • C)Mutation theory
    • D)Genetic drift

    Answer: B) Natural selection

    Darwin's theory of evolution is based on the concept of natural selection where individuals with advantageous traits survive and reproduce. Over generations, these beneficial traits become more common in the population.

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