MODEL PAPER 9 — BIOLOGY STD 11 Science — Question

While teaching cell division in the class, teacher told that during meiosis, the chromosome number is reduced to half of the parent, whereas during mitosis, the number remains the same. Seema was not able to recognise what teacher explained in the class and asked her elder brother, a botany student, the need of reducing chromosomes during gamete formation and what will happen if chromosome number will not reduced to its half. He explained the concept in detail to Seema.

1. In which part of the organisms does meiosis occur?
2. How does meiosis help in evolution?
3. Give the significance of meiosis.
4. What value is expressed in the behaviour of Seema's elder brother?

Can all the four chambers of the human heart experience systole simultaneously? Explain justifying your answer.

Discuss the types of enzyme cofactors that are required for the efficient activity of enzymes.

Explain arithmetic growth in plants.

How is the study of plant anatomy useful to us?

Describe the role played by diaphragm and intercostal muscles in inspiration.

Neha while learning for her test, got confused how aerobic pyruvic acid is transported to mitochondria for further oxidation. She asked her elder sister (who is a graduate in biology) about this and also asked her to explain the same process in detail. Her sister explained her that it gets completely oxidised into CO₂ and water along with the formation of ATP.

1. Mention the sites in the mitochondria, where these events occur.
2. What happens to pyruvic acid before it enters 'Krebs' cycle?
3. Write the summary equation for the 'Krebs' cycle.
4. Mention the value implicit through Neha's character.

Explain the autoregulatory mechanism of GFR.

What is the nature of cell-walls in diatoms?

Describe the role of different regions of a nephron in urine formation.