Regularidades del proceso de selección, uso y evaluación del uso

! (b) Synaptonemal complex I (c) A n t e p h a s e ! (d) Aster j (e) Interphase I | 2. (a) Somatostatin

j (b) X - This hormone is secreted by the hypothalamus | and some extraneural tissues, including the | gastrointestinal tract and pancreas (5 or D cells of islet j of langerhans).

! Y - Somatostatin is a paracrine whose secretion is I stimulated by glucose; glucagon and gut hormones. : 3. (a) Clitellum - Clitellum, a external feature, is a I girdle like thick band of glandular tissue which completely and permanently surrounds the segments ; 14 to 16 in a mature worm (earthworm). It secretes mucus, albumen and an egg case or cocoon for eggs. (b) Cnidoblast - Cnidoblast is an oval or rounded cell with a conspicious basal nucleus lying on one side. It is called nematoblast, found only in the ectoderm of the phylum cnidaria or coelenterate. It contains a nematocyst; a fluid filled sac within which lies a long hollow coiled thread. When a small sensory projection (called cnidocil) on the surface of the thread cells is touched (eg. by prey) the thread is shot out and adheres to the prey, coils round it, or injects poison into it.

(c) Statocyst - Statocyst is a balancing organ found in many invertebrates [eg, Pila (phylum mollusca)]. It consists of a fluid filled sac lined with sensory hairs and contains granules of calcium carbonate, sand etc (statoliths). As the animal moves statoliths stimulates 28

different hairs, giving a sense of the position of the body or part of it.

(d) Oncosphere — Oncosphere is a six hooked larva (hexacanth) having a pair of large penetration glands, of a tapeworm. If ingested by a suitable intermediate host such as a pig or an ox, the larva will use its hook to penetrate the wall of the intestine. The larva s u b s e q u e n t l y migrates to the muscles, where it develops into a cysticercus.

(e) Sporozoite - Sporozoites are small spindle shaped, slightly curved or sickle shaped and uninucleate organisms. It is formed as a result of sporogony during the life cycle of a sporozoan (eg. Plasmodium). It represent the infective form of the parasite. Sporozoites are formed by the repeated divisons of the contents of the oocyst inside the body of the mosquito. The released sporozoites ultimately pass into the insects salivary glands and await transmission to a human host at the next blood meal.

4. (a) Statement II and III (b) Statement I.

5. (a) Hair on the scalp provides insulation from cold for the head.

- The hair of eyelashes and eyebrows helps keep dust and perspiration out of the eyes.

- Hair in nostrils helps keep dust out of the nasal cavities.

- Any other hair on our bodies no longer serves any function, but is an evolutionary remnant. (b) Cranial nerve VII, the facial nerve, carries taste sensations from the anterior two thirds of the tongue (excluding the circumvallated papillae) and soft palate; cranial nerve IX, the glossopharyngeal nerve, carries taste sensations from the posterior one third of the tongue (including the circumvallated papillae) while a branch of the cranial nerve X, vagus nerve, carries some taste sensations from the back of the oral cavity

{i.e. pharynx and epiglottis).

(c) Direct control of water excretion in the kidneys, is exercised by the anti-diuretic hormone (ADH) secreted by the posterior lobe of pituitary gland. The hormone associated with the reabsorption of salt is aldosterone, a steroid hormone produced by the adrenal cortex. Aldosterone promotes the excretion of potassium ions and the reabsorption of sodium ions.

(d) The red blood cells are diffused by bicarbonate | ion, to be carried in the plasma. The reaction gives off j H* and lowers the blood pH. When blood in the lungs I is diffused out by carbon dioxide, the reaction reverse I the direction and the pH is raised.

! (e) The mucociliary escalator extends from the top of ! the trachea all the wav down to the bronchioles. The

! J

j dust will adhere to the sticky mucous and the cilia helps propel it back up the trachea, to where it is either swallowed or coughed up.

6.(a) Nicotine

- Stimulates passage of nerve impulses - Causes the muscles to relax and cause the

release of adrenaline - increases blood pressure

- causes retardation of the growth of the foetus in pregnant woman

(b) Alcohol - affects liver.

- causes fatty liver syndrome which leads to cirrhosis.

- affects coordination of body parts. - decreases blood sugar level. (c) Tranquillisers

- depress brain activity.

- produces feeling of calmness, relaxation and drowsiness.

- reduce tension and anxiety. (d) Hallucinogens

- alters a p e r s o n ' s t h o u g h t s , f e e l i n g s and perceptions. They can 'see sound' and 'hear colour'.

- causes chronic psychosis. - causes severe damage to the CNS. (e) Caffeine

- stimulates the nervous system. - it is diuretic.

7. (a) — (ii); (b) - (v). (vi), (vii), (x) (c) - (iii), (iv), (ix); (d) - (viii); (e) - (i) 8. Structure V - I ; Structure W - IV

j Structure X — II ; Structure Y - 1 ; Structure Z — I 9. (a) - I m m u n o g l o b u l i n s , a g g l u t i n a t i o n , opsonisation, neutralization, IgG.

like methane, hydrogen sulphide and ammonia. They kill the bloom forming plants as well. The water body comes to have foul smell, brown colouration, bad taste and oil.

(ii) The process is b i o m a g n i f i c a t i o n . Persistent pesticides (e.g., o r g a n o c h l o r i n e or chlorinated hydrocarbons like DDT) pass into food chain and increase in amount per unit weight of organisms with the rise in trophic level due to their accumulation in fat. The phenomenon is called biomagnification/ bioconcentration/biological amplification, e.g., 0.01- 0.05 parts per billion in water, 5 parts per billion or 0.025 ppm in phytoplankton, 0.123 ppm in zooplankton, 1.04 ppm in clams and small fish, 4.83 ppm in predator fish and 124 ppm in fish eating birds like Sea Gulls. 19. (a) A - Marginal (eg Pisum)

B - Axile (eg Hibiscus), C - Parietal (eg Cucurbit) D - Free central (eg Silene), E - Basal (eg Sunflower) F - Superficial (eg Nymphaea)

0=

Fig : D i a g r a m m a t i c r e p r e s e n t a t i o n of life cycle of Funaria. 20. (a) (i) 13 : 3 ; (ii) 9 : 6 : 1

(b) (i) Jacob and Monad (1961)

(ii) Operon = Structural gene + regulator gene + promoter gene + operator gene.

(iii) CAP binding site 3 Structural genes

I P 0 z y a Transcription m-RNA I Repressor protein Polycistronic m-RNA Translation ^ j ^ (3-galacto- Permease Trans-

sidase acetylase Fig : D i a g r a m of lac o p e r o n

(iv) Tryptophan operon (try operon) in bacteria is a repressible operon. Here repressor is inactive and it becomes active as DNA binding protein only when c o m p l e x e d with a co-repressor (tryptophan). In absence of tryptophan, the operator site is open to binding by RNA polymerase, which transcribes the structural genes of tryptophan operon, leading to production of enzymes that synthesize tryptophan. When tryptophan becomes available, the enzymes of tryptophan synthetic pathway are no longer needed and tryptophan (co-repressor)-repressor complex blocks transcription. Thus the regulation of this operon is a negative control.