Class 12 Biology

Few problems along with their solutions from this chapter are given follows:

Q. The term 'clone' cannot be applied to offspring formed by sexual reproduction because

(a) Offspring do not possess exact copies of parental DNA

(b) DNA of only one parent is copied and passed on to the offspring

(c) Offspring are formed at different times

(d) DNA of parent and offspring are completely different

Ans. (a) Offspring do not possess exact copies of parental DNA

Explanation: In the case of sexual reproduction DNA of both parents, (i.e., male and female gametes) is copied and passed on to the offspring after fusion which is responsible for some alteration in genotype. The offspring, thus formed do not possess exact copies of parental DNA.

Q. Between an annual and a perennial plant, which one has a shorter juvenile phase? Give one reason.

Ans. Juvenile phase is the period of growth in an organism after its birth and before it reaches reproductive maturity.

Now as the entire life cycle of an annual plant is shorter and has to be completed in one growing season, its juvenile phase is shorter than that of a perennial plant.

Q. The number of taxa exhibiting asexual reproduction is drastically reduced in higher plants (angiosperms) and higher animals (vertebrates) as compared with lower groups of plants and animals. Analyse the possible reasons for this situation.

Ans. Higher plants (angiosperms) and higher animals (vertebrates) have a more complex structural organisation. Mitosis involved in asexual reproduction cannot produce all kinds of differentiation which is required for making various types of tissues in higher organisms. Thus, they have evolved an efficient mechanism of sexual reproduction which enables them to:

• ensure healthy progeny
• produce genetically varied offspring that adapt to the environment changes and have survival in all climatic conditions
• ensure the genetic recombination that results in variation which gives rise to evolution.

• Each chapter of NCERT Exemplar Class 12 Biology book starts with a brief overview of the chapter followed by solved examples and unsolved exercises. All the problems given in this book are very important for CBSE Class 12 board examination and other competitionve examinations.

  Main topics discussed in Class 12 Biology, Chapter 1 - Reproduction in Organisms, are:

  • Asexual reproduction
  • Sexual reproduction
  • Pre-fertilisation events
  • Post-fertilisation events.