Biology – Class XII – Student Support Material (SSM 2025–26)

SECTION A – Objective Type Questions (1 Mark Each)

Section A mainly contains:

Multiple Choice Questions (MCQs)

Assertion–Reason Questions

Case-Based Questions

This section checks your basic understanding of concepts, definitions, and important facts from each chapter.

For example, in Chapter 1: Sexual Reproduction in Flowering Plants, Section A asks questions about the structure of flower parts such as androecium and gynoecium, the layers of microsporangium, double fertilization, endosperm, and types of pollination. These questions test whether you clearly understand the structure and functions of reproductive parts and important processes like syngamy and triple fusion.

Similarly, in Chapter 2: Human Reproduction, Section A includes questions about the menstrual cycle, hormones like LH, FSH, hCG, structure of sperm, fertilization, and placenta. Here, you must know which hormone performs what function, where fertilization occurs, and how pregnancy is maintained.

In Chapter 3: Reproductive Health, objective questions test knowledge about contraceptive methods, STDs, IUDs, ART techniques like IVF and ZIFT, and government measures for population control.

In Genetics and Evolution, Section A includes questions on Mendel’s laws, co-dominance, incomplete dominance, ABO blood groups, chromosomal theory of inheritance, linkage, recombination, Hardy-Weinberg principle, and human evolution.

In Biotechnology, questions test knowledge about recombinant DNA technology, restriction enzymes, vectors, PCR, insulin production, Bt crops, and gene therapy.

In Ecology, questions focus on population growth, ecological pyramids, biodiversity, food chains, and conservation strategies.

Section A mainly checks whether:

You remember definitions correctly.

You understand basic biological processes.

You can apply simple reasoning.

Even though it carries fewer marks, it is very important because it builds your foundation.

SECTION B – Very Short and Short Answer Questions (2–3 Marks)

Section B requires you to write answers in short paragraphs. You must explain concepts clearly, not just write definitions.

For example, in Sexual Reproduction in Flowering Plants, Section B may ask you to explain pollen-pistil interaction. In this answer, you must describe how pollen grains land on the stigma, how compatible pollen is recognized, how the pollen tube grows through the style, and how it enters the ovule through the micropyle. You must clearly explain the biological mechanism involved.

In Human Reproduction, you may be asked to explain hormonal regulation of the menstrual cycle. In this case, you must describe how FSH stimulates follicle growth, how LH causes ovulation, and how progesterone prepares the uterus for implantation. Writing only the names of hormones is not enough; you must explain their roles properly.

In Reproductive Health, you may be asked to explain how copper-releasing IUDs work. You should mention that copper ions suppress sperm motility and increase phagocytosis of sperms, thereby preventing fertilization.

In Genetics, Section B questions may ask you to explain Mendel’s Law of Segregation. You must describe how alleles separate during gamete formation and how each gamete carries only one allele.

You may also be asked to explain incomplete dominance using the example of Mirabilis jalapa, where red and white flowers produce pink flowers in F1 generation. Here, you must explain both genotypic and phenotypic ratios.

In Evolution, you may be asked to explain Darwin’s theory of natural selection. You must describe variation, struggle for existence, survival of the fittest, and inheritance of favorable traits.

In Ecology, short answers may require explanation of ecological pyramids or population growth curves (J-shaped and S-shaped).

Section B tests:

Conceptual clarity

Ability to explain biological mechanisms

Logical thinking

Understanding of cause and effect

Your answers must be structured and meaningful.

SECTION C – Long Answer Questions (5–6 Marks)

Section C requires detailed answers. These questions test your deep understanding, analytical ability, and structured writing skills.

For example:

In Sexual Reproduction in Flowering Plants

You may be asked to explain double fertilization in detail. Here, you must describe how one male gamete fuses with the egg (syngamy) to form a zygote and the other fuses with polar nuclei (triple fusion) to form the primary endosperm nucleus. You must also explain the development of endosperm and embryo.

In Human Reproduction

A long question may ask you to draw and explain the female reproductive system and describe phases of the menstrual cycle. You must clearly explain the menstrual phase, follicular phase, ovulatory phase, and luteal phase, along with hormonal changes.

In Genetics

You may be asked to explain Mendel’s dihybrid cross. Here, you must describe the cross between RRYY and rryy plants and explain how independent assortment leads to 9:3:3:1 phenotypic ratio. You must also explain the Punnett square properly.

Another important long question may involve explaining chromosomal theory of inheritance and how Sutton and Boveri connected chromosomes with Mendel’s laws.

In Molecular Basis of Inheritance

You may be asked to explain DNA replication. In such an answer, you must describe semi-conservative replication, the role of helicase, DNA polymerase, leading and lagging strands, and Okazaki fragments.

You may also need to explain transcription and translation under the central dogma of molecular biology.

In Biotechnology

A long question may ask you to explain the steps of recombinant DNA technology. You must describe isolation of DNA, cutting with restriction enzymes, insertion into vectors, transformation, cloning, and selection of recombinants.

In Ecology and Environment

You may be asked to explain energy flow in an ecosystem. You must describe producers, consumers, decomposers, trophic levels, and the 10% law of energy transfer.

Another important question may involve biodiversity conservation. You must explain in-situ conservation (national parks, biosphere reserves) and ex-situ conservation (zoos, botanical gardens, gene banks).