Human Reproduction — BIOLOGY STD 12 Science — Question

Write a short note on Double fertilisation.

Given below is an equation describing the Species-Area relationship between species richness and area for a wide variety of taxa as angiosperm plants, birds, bats etc.
S = CA^Z
a. Give a graphical representation of the given equation showing Species-Area relationship.
b. What does S represent in the given equation?
c. What is the value of Z (regression coefficient) for frugivorous birds and mammals in the tropical forests of different continents?

A homozygous tall pea plant with green seeds is crossed with a dwarf pea plant with yellow seeds.

1. What would be the phenotype and genotype of F₁?
2. Work out the phenotypic ratio of F₂ generation with the help of Punnett  square.

Under natural immunity, how are we automatically protected from environmental germs through protective processes? ###How do innate immunity prevent the entry of external pathogenic factors? Explain.

Trace the life-cycle of malarial parasite in the human body when bitten by an infected female Anopheles.

What is cancer? How is a cancer cell different from the normal cell? How do normal cells attain cancerous nature?

Write a note on structure of t-RNA

Define co-extinction and give a example.

With respect to Messelson and Stahl’s Experiment, answer the following questions:

1. Identify the method used to distinguish between heavy and light isotopes of nitrogen.
2. With the help of diagrams, compare the results for the DNA isolated after 20 minutes of experiment with the DNA which was isolated after 40 minutes.

Answer the following questions:
What is meant by ADA deficiency? How is gene therapy a solution to this problem? Why is it not a permanent cure?