Human Reproduction — BIOLOGY STD 12 Science — Question

How do organisms cope with stressful external environmental conditions which are localised or of short duration?

Explain antibiotic resistance observed in bacteria in light of Darwinian selection theory.

Transplantation to save certain patients often fails due to rejection by the patient. What is transplantation? Which type of immune response is responsible for such rejections?

Why should the spraying of DDT as an insecticide on vegetable crops be banned? Explain.

Classify the following as examples of homology and analogy:

(i)	Mouth parts of cockroach and butterfly
(ii)	Hearts of rabbits and human beings
(iii)	Eyes of octopus and mammals
(iv)	Sweet potato and potato
(v)	Stings of honey bee and scorpion
(vi)	Tendrils of Lathyrus and tendrils of Gloriosa

One of the twins born to parents having normal colour vision was colour blind whereas the other twin had normal vision. Work out the cross. Give two reasons how it is possible.

Rearrange the following in the correct sequence to accomplish an important biotechnological reaction:

1. In vitro synthesis of copies of DNA of interest.
2. Chemically synthesised oligonucleotides.
3. Enzyme DNA-polymerase.
4. Complementary region of DNA.
5. Genomic DNA template.
6. Nucleotides provided.
7. Primers.
8. Thermostable DNA-polymerase (from Thermus aquatics).
9. Denaturation of ds-DNA.

Describe two natural methods of birth control, other than lactational amenorrhoea.

How do mycorrhizal fungi help the plants harbouring them?

1. Name the ancestors of progymnosperm.
2. Name the ancestors of herbaceous and arborescent lycopod.
3. Name the ancestors of cycads.