Biology -1999

Q1. Name the process in which bacteriophage picks-up a piece of DNA from one bacterial cell and transfers the same to another bacterial cell on infection.
Ans1. Transduction.

Q2. Which fraction of soil water is readily available to plants for absorption.
Ans2. Capillary water fraction .

Q3. What protects nitrogenase?
Ans3. ‘Leghemoglobin’ combines with oxygen and maintains anaerobic environment to protect nitrogenase.

Q4. Name two plants that produce rhizomes.
Ans4. Ginger, Turmeric.

Q5. Why is oxytocin called as ‘Birth Hormone’?
Ans5. Oxytocin helps in uterine contraction and the onset of labour at the time of child-birth.

Q6. From which germ layers do the following organs differentiate :
(i) Kidney
(ii) Urinary bladder

Ans6. Kidney and the urinary bladder differentiate from mesoderm.

Q7. What provided energy for abiotic synthesis on the primitive earth?
Ans7. ‘Lightning and solar radiation’ provided energy for abiotic synthesis on the primitive earth.

Q8. Name the two curable sexually transmitted diseases.
(i) Syphilis, and
(ii) gonorrhoea are curable sexually transmitted diseases.

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