Q1. At what stage the embryo is implanted in the uterus of the mother in case of a test tube baby? 

Ans1. 32-celled Morula.

Q2. Human heart is Myogenic yet a parasympathetic nerve can reduce the heart rate. Name the nerve.

Ans2. Vagus Nerve.

Q3. Which of the following diseases could be avoided by analysing the pedegree of parents – Klinefelter’s syndrome, Haemophilia, Amoebiasis.

Ans3. Haemophilia.

Q4. Name the functional contractile unit of the muscle.

Ans4. Sarcomere.

Q5. Name any two synthetic auxins used in agriculture.

Ans5. (i) NAA (naphthaleneacetic acid)

(ii) 2,4 D (2,4-dichlorophenoxyacetic acid)

Q6. What is pulvinus?

Ans6. Pulvinus is the swollen base of the leaf in many members of the bean family. It is responsible for sleep movements.

Q7. Name the fluid in which membranous labyrinth of the inner ear floats.

Ans7. Perilymph.

Q8. In a round worm the volume of the body increases due to the growth of the body cells without increase in their number. What do you call this type of growth?

Ans8. Auxetic growth.

Q9. Why is the cleavage in mammals referred to as simple holoblastic?

Ans9. Cleavage in mammals is referred to as Simple Holoblastic because in the absence of any Yolk in the mammalian egg, it divides completely. This means the cleavage furrow divides the egg or blastoderms completely.

Q10. Name the tissue that lines the urinary bladder. State any one advantage of this tissue being present there.

Ans10. The urinary bladder is lined by Transitional Epithelium. The advantage of having this stretchable tissue is that it may be considerably stretched without getting torn when the bladder is filled with urine.

Q12. Why is human male referred to as heterogametic?

Ans12. Human male has an X and a Y chromosome in its karyotype. Thus to make a male zygote, gametes of two different karyotypes are required. Therefore human male is called heterogametic.

Q13. What are the events that take place at the point of stimulation of an axon?

Ans13. An unexcited axon has the Resting Membrane Potential on its membrane and is in the polarised State. In this state the inner side of the membrane is negative as compared to the outer membrane. A threshold stimulus causes the resting membrane potential to become the Action Potential, i.e. the inner side of the membrane becomes electropositive to its outside. This action potential propagates along the membrane of the nerve fibre as the nerve impulse. As the impulse has moved away, the membrane becomes Depolarised i.e., it becomes negatively charged on the inner side.

Q14. Write the transcribed m-RNA from the DNA strand with the base sequence of TAG TAC ACT. What is the specific term used for the last codon of the transcribed m-RNA in this case?

Ans14. The transcribed mRNA from the given sequence will be AUC AUG UGA. Last codon UGA is one of the nonsense Stop-codons and would terminate the translation of the polypeptide after it is encountered during the translation.

Q15. Why is blood group identification not required while transfusing serum?

Ans15. The serum is a cell-free fluid, which forms when the blood has clotted and the thrombus has separated from it. Since the blood group deciding antigens reside on the RBCs which are not present in the serum, hence it can be transfused to anyone without the customary requirement of the blood group identification.

Q16. The primitive earth had reducing atmosphere to enable abiotic origin of life. What put an end to it?

Ans16. The emergence of green bacteria and plants with the ability to produce photosynthetic oxygen caused heavy build up of oxygen in the earth’s atmosphere, which caused the reducing environment to be changed into an oxidising environment.

Q17. How a sickle-cell carrier has an advantage over the rest of the human population in a Malaria ridden area?

Ans17. A defective form of haemoglobin is found in the RBCs of the Sickle-cell carrier. They have sickle-shaped RBCs, which are highly inefficient in binding oxygen. However, a sickle shaped RBC effectively kills the malaria parasite too, which harbors in it. Thus individuals homozygous for Sickle-cell trait have a better survivability in the event of malaria epidemics and thus natural
selection has not eliminated this trait in those geographical locations in the world, where there is a prevalence of malaria.

Q20. Define Cancer. How are cancers broadly classified pathologically? Name one major cancer in women and one major cancer in men in India.

Ans20. Pathologically, cancers may be broadly classified into three major catagories :
(i) Carcinomas, which are malignant growths of the epithelial (ectodermal) tissues.
(ii) Sarcomas, which are malignant growths of the mesodermal tissues such as bone, muscle, lymph nodes and the likes.
(iii) Leukaemias, which are unchecked proliferation of blood cells, and there precursors in the bone marrow.
In India the major form of cancer in women is the uterine-cervical cancer and it is the cancer of the mouth and throat in men.

Q21. State Lamarck’s theory on evolution. Who disapproved it and how?

Ans21. Lamarck’s theory is the ‘Theory of inheritance of acquired characters’.
According to this theory organisms undergo certain changes to adapt themselves to the environment. These characters acquired during the lifetime are passed on to progeny. Weismann refuted Lamarckism by showing that even if tails of newborn mice were cut off generation after generation, no shortening of tails was observed in any subsequent generations.

Q22. A farmer has been advised to sow soybean seeds inoculated with a bacterial culture. Name the bacterium in the culture. How is this bacterium useful to the crop?

Ans22. The bacterium is Rhizobium.
This bacterium produces nodules in the roots of leguminous plants and fixes atmospheric nitrogen.
The inoculation of legume seed with Rhizobium will ensure better nitrogen fixation and yields.

Q24. Name any three organs homologous to human hand. Why are they considered homologous?

Ans24. The flippers of seal, the wings of bats, and the paws of cats are the organs homologous to the human hand. They are considered homologous because although they perform different functions and look superficially different, they have fundamentally similar plan and the similar structure.
Moreover the pattern of their embryonic development is essentially similar. Such organs in different animals with same basic structure and developmental origin are called homologous organs.

Q25. Give the full form of ADH. Name the gland that secretes it. Under what condition of the body is it released? What is its role in forming hypertonic urine? What disease is caused due to the failure of secretion of this hormone?

Ans25. ADH stands for Antidiuretic Hormone. It is secreted by the posterior pituitary gland. ADH is secreted when the water content of the body is less than the required, and therefore has to be conserved. ADH secretion causes the walls of the DCT, collecting tubule and collecting duct to become
permeable to water. The tissue surrounding to them is hypertonic due to the active reabsorption of Na⁺ into it and due to the retention of Na⁺ and urea by the counter-current system of vasa rectae. So, water is progressively reabsorbed from the filtrate flowing along the DCT, collecting tubule and collecting duct (rendered permeable by action of ADH) into the surrounding
hypertonic tissue and the peritubular capillaries. The filtrate in the collecting duct consequently becomes hyperosmotic and a strongly hypertonic urine flows out into the renal pelvis.

Q26. Give one reason why lysozyme is considered an enzyme and not a hormone? How does it defend the body? Name any two secretions in humans, which contain lysozyme.

Ans26. Lysozyme is not a hormone because it does not satisfy the following criteria required for a protein to become a hormone :
(i) It is not secreted in response to any change in the internal or external environment of the body,
(ii) it is not transported by blood,
(iii) it has no specific target organ of its own,
(iv) it does not stimulate or inhibit specific biological processes in the targeted organs to modify their activity.
Lysozyme destroys the cell wall of many bacteria and thus prevents many infections.