Q27 of 27 Page 1

Differentiate between spermatogenesis and oogenesis.

OR


‘Parturition is induced by a complex Neuro endocrine mechanism’. Justify


OR


Gestation period refers to the average duration of human pregnancy, i.e. about 9 months. Vigorous contractions at the end of pregnancy cause the ejection or delivery of the foetus and are called parturition (child birth). Parturition is induced by a complex neuroendocrine mechanism. The signals for parturition arise from a fully developed foetus and placenta which induce mild uterine contractions called foetal ejection reflex. This triggers the release of oxytocin from maternal pituitary. Oxytocin acts on uterine muscles and causes stronger uterine contractions which stimulate further secretion of oxytocin. The stimulatory reflex between uterine contractions and oxytocin secretion continues resulting in stronger contractions and finally leads to expulsion of the baby out of the uterus through the birth canal – parturition.


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23

Study the given pedigree chart and answer the questions that follow:


(a) Is the trait recessive or dominant?


(b) Is the trait sex-linked or autosomal?


(c) Give the genotypes of the parents shown in generation I and their third child shown in generation II and the first grandchild shown in generation III.


OR


Haemophilia is a sex-linked recessive disorder of humans. The pedigree chart given below shows the inheritance of Haemophilia in one family. Study the pattern of inheritance and answer the questions given.


pedigree.png


(a) Give all the possible genotypes of the members 4, 5 and 6 in the pedigree chart.


(b) A blood test shows that the individual 14 is a carrier of haemophilia. The member numbered 15 has recently married the member numbered 14. What is the probability that their first child will be a haemophilic male.? Show with the help of Punnett square.

 24

(a) In a pond, there were 200 frogs. 40 more were born in the year. Calculate the birth rate of the population.

(b) Population in terms of number is not always a necessary parameter to measure population density. Justify with two examples.

 25

People living in the coastal areas are forced to evict their dwelling units as the sea has inundated into the land areas. State the possible reasons and suggest measures that could be taken to reduce the deleterious changes in the environment.

OR


A young sperm whale, 33-foot long was found dead off the coast. It had a large amount of human trash like trash bags, polypropylene sacks, ropes, net segments etc. amounting to 29 kilograms in its digestive system. The whale died because of inflammation of the abdominal lining. Analyze the possible reasons for such mishaps and suggest measures that can be taken to reduce such incidents.

 26

Aneuploidy of chromosomes in human beings results in certain disorders. Draw out the possibilities of the karyotype in common disorders of this kind in human beings and its consequences in individuals.

OR


In a dihybrid cross, white-eyed, yellow bodied female Drosophila was crossed with red-eyed, brown bodied male Drosophila. The cross produced 1.3 per cent recombinants and 98.7 progeny with parental type combinations in the F2 generation. Analyze the above observation and compare with the Mendelian dihybrid cross.