CBSE Class 12 Biology Syllabus

Biology syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Biology in CBSE Class 12, not a summary of it.

1. 1

   Reproduction

   4 topics

   • Reproduction in organisms
   • Sexual reproduction in flowering plants
   • Human reproduction
   • Reproductive health
2. 2

   Genetics and Evolution

   3 topics

   • Heredity and variation
   • Molecular basis of inheritance
   • Evolution
3. 3

   Biology and Human Welfare

   3 topics

   • Health and Disease
   • Improvement in food production
   • Microbes in human welfare

Biology flashcards for CBSE Class 12

22 of 70 cards from the Biology deck — real questions with worked answers.

1. What is the difference between asexual and sexual reproduction in terms of offspring and gamete fusion?

   Asexual reproduction involves a single parent, no gamete fusion, and produces genetically identical offspring (clones). Sexual reproduction involves two parents, fusion of male and female gametes, and produces genetically variable offspring.

2. Define 'juvenile phase' (vegetative phase) in organisms.

   It is the period of growth before an organism reaches reproductive maturity, during which it cannot reproduce sexually.

3. What is oestrus cycle and in which animals does it occur?

   The oestrus cycle is the cyclical changes in reproductive activity seen in non-primate mammals (e.g., cows, dogs, tigers) during the breeding season.

4. What is the difference between oviparous and viviparous animals?

   Oviparous animals lay fertilized/unfertilized eggs that develop outside the body (e.g., birds, reptiles). Viviparous animals give birth to young ones after internal development (e.g., most mammals).

5. Name two examples of asexual reproduction by special structures: one in Hydra and one in sponges.

   Hydra reproduces by budding; sponges reproduce by gemmules.

6. What is the function of the tapetum in an anther?

   The tapetum is the innermost layer of the microsporangium wall that nourishes the developing pollen grains (microspores).

7. What are the two layers of the wall (exine and intine) of a pollen grain made of?

   The exine (outer layer) is made of sporopollenin, which is highly resistant; the intine (inner layer) is made of cellulose and pectin.

8. Describe the structure of a typical anatropous ovule's embryo sac (female gametophyte).

   The mature embryo sac is 7-celled and 8-nucleate: one egg cell and two synergids (egg apparatus), three antipodal cells, and one central cell with two polar nuclei.

9. What is double fertilisation in angiosperms?

   One male gamete fuses with the egg cell to form the zygote (syngamy, 2n); the other fuses with the two polar nuclei to form the primary endosperm nucleus (triple fusion, 3n).

10. What is the ploidy of the endosperm in angiosperms and why?

    The endosperm is triploid (3n) because it forms from triple fusion of one male gamete (n) with two polar nuclei (n + n).

11. What is apomixis?

    Apomixis is the formation of seeds without fertilisation, a form of asexual reproduction mimicking sexual reproduction (e.g., in some Asteraceae and grasses).

12. What is polyembryony? Give an example.

    Polyembryony is the occurrence of more than one embryo in a single seed, as seen in citrus and mango.

13. Differentiate geitonogamy from xenogamy.

    Geitonogamy is pollination between two flowers of the same plant (genetically self-pollination). Xenogamy is pollination between flowers of different plants of the same species (genetically cross-pollination).

14. Name two outbreeding devices that prevent self-pollination in flowering plants.

    Examples include: dichogamy (different maturation times of pollen and stigma), self-incompatibility, herkogamy, and unisexuality (dioecy).

15. Where does spermatogenesis occur and what hormone stimulates it?

    Spermatogenesis occurs in the seminiferous tubules of the testes; it is stimulated by FSH (along with testosterone).

16. What is the role of Sertoli cells and Leydig (interstitial) cells in the testis?

    Sertoli cells nourish the developing sperm; Leydig (interstitial) cells secrete testosterone (androgens).

17. List the four phases of the menstrual cycle in order.

    Menstrual phase, follicular (proliferative) phase, ovulatory phase, and luteal (secretory) phase.

18. Which hormone surge triggers ovulation, and on roughly which day of a 28-day cycle does ovulation occur?

    A surge of LH (luteinizing hormone) triggers ovulation, which occurs around day 14.

19. What is the corpus luteum and which hormone does it secrete?

    The corpus luteum is formed from the ruptured Graafian follicle after ovulation; it secretes progesterone (and some estrogen) to maintain the endometrium.

20. Define implantation in human reproduction.

    Implantation is the attachment of the blastocyst to the uterine endometrium, occurring about 6-7 days after fertilisation.

21. What is the function of the placenta? Name two hormones it produces.

    The placenta facilitates exchange of nutrients, gases, and wastes between mother and fetus; it produces hormones such as hCG, hPL, estrogen, and progesterone.

22. What hormone is the basis of pregnancy detection tests and where is it produced?

    Human chorionic gonadotropin (hCG), produced by the placenta (trophoblast), is detected in urine for pregnancy tests.

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