CBSE Class 12 Biology Important Questions

1. Explain the process of double fertilisation in flowering plants and its significance.

Answer: Double fertilisation involves two male gametes. One fuses with the egg to form a diploid zygote, and the other fuses with two polar nuclei to form the triploid endosperm. This process ensures the simultaneous development of the embryo and the endosperm, which nourishes the developing seed.

2: Describe the hormonal regulation of the menstrual cycle in humans.

Answer: The menstrual cycle is controlled by hormones like FSH, LH, estrogen, and progesterone. FSH stimulates the growth of ovarian follicles, LH triggers ovulation, estrogen thickens the uterine lining, and progesterone maintains the lining. A drop in these hormone levels causes menstruation.

3: What are the different methods of birth control, and how do they help in reproductive health?

Answer: Methods include barrier methods (condoms), hormonal methods (birth control pills), IUDs, and sterilisation (vasectomy and tubectomy). These methods help prevent unwanted pregnancies, control population growth, and reduce the risk of sexually transmitted infections (STIs).

4: Explain Mendel’s law of segregation with a monohybrid cross example.

Answer: Mendel’s law of segregation states that allele pairs separate during gamete formation, and each gamete carries only one allele for a gene. In a monohybrid cross of pea plants (tall and dwarf), the F1 generation shows all tall plants, but the F2 generation exhibits a 3:1 ratio of tall to dwarf, showing the separation of alleles.

5. Describe the structure of DNA and its role in protein synthesis.

Answer: DNA is a double helix composed of nucleotide bases (adenine, thymine, cytosine, guanine), a sugar-phosphate backbone, and is arranged in antiparallel strands. DNA carries genetic information, which is transcribed into mRNA, and then translated into proteins in the ribosomes during protein synthesis.

6. What is the difference between homologous and analogous organs? Give examples.

Answer: Homologous organs have the same origin but different functions (e.g., the forelimbs of humans and the wings of birds). Analogous organs have different origins but perform similar functions (e.g., wings of birds and insects). These examples show evolutionary patterns of divergence and convergence, respectively.

7. What are the main barriers to immunity in the human body?

Answer: The main barriers to immunity include physical barriers (skin and mucous membranes), chemical barriers (stomach acid, enzymes), and biological barriers (immune cells like white blood cells). These barriers protect the body from infections and diseases.

8. How do microbes contribute to human welfare in the production of antibiotics?

Answer: Microbes like bacteria and fungi produce antibiotics, which are used to kill or inhibit the growth of harmful microorganisms. For example, Penicillium produces penicillin, an antibiotic that treats bacterial infections.

9: Explain the role of restriction enzymes in biotechnology.

Answer: Restriction enzymes act as molecular scissors, cutting DNA at specific sequences. This allows scientists to isolate desired genes and insert them into vectors for genetic engineering, playing a critical role in processes like gene cloning.

10: What are the effects of habitat loss on biodiversity?

Answer: Habitat loss leads to a reduction in biodiversity as species lose their natural habitats, resulting in population decline and, in severe cases, extinction. This affects ecosystem balance and reduces genetic diversity, which is essential for species adaptation.

Here are 10 important questions from all chapters. For more detailed, chapter-wise questions, refer to the table above and download the PDF. This will help you gain a better understanding of each chapter and enhance your exam preparation.

How do Biology Important Questions Class 12 Help you with Exams?

• Biology important questions for Class 12 highlight the most important topics that are frequently asked in exams.

• Solving these questions helps students understand concepts more deeply, improving their overall grasp of the subject.

• These questions provide excellent practice for answering different types of questions, boosting exam readiness.

• Practising important questions helps students learn how to manage their time effectively during the exam.

• Familiarity with commonly asked questions reduces exam anxiety and increases confidence.

• These questions help students organise their revision in a more structured and efficient way.

Vedantu CBSE Class 12 Biology Important Questions serve as a valuable resource for students preparing for their exams. These questions not only cover essential concepts but also help reinforce understanding and boost confidence. By practising these questions, students can identify their strengths and weaknesses, enabling them to focus on areas that need improvement. Using Vedantu’s notes will simplify complex topics, making studying more effective and enjoyable.

Additional Study Materials for Class 12 Biology