Long Answer Type(a) Explain giving reasons why the tourists visiting Rohtang Pass or Mansarovar are advised to resume normal active life only after a few days of reaching there.
(b) It is impossible to find small animals in the polar regions. Give reasons.
Describe Frederick Griffith’s experiment on Streptococcus pneumonia. Discuss the conclusion he arrived at.
(a) Explain a monohybrid cross taking seed coat colour as a trait in Pisum sativum. Work out the cross upto F2 generation.
(b) State the laws of inheritance that can be derived from such a cross.
(c) How is the phenotypic ratio of F2 generation different in a dihybrid cross?
The following is the illustration of the sequence of ovarian events “a†to “i†in a human female:
(a) Identify the figure that illustrates corpus luteum and name the pituitary hormone that influences its formation.
(b) Specify the endocrine function of corpus luteum. How dies it influence the uterus? Why is it essential?
(c) What is the difference between d and e?
(d) Draw a neat labeled sketch of Graafian follicle.
(a) Figure g illustrates corpus luteum. Rapid secretion of leutinizing hormone LH from pituitary gland induces the rupture of Graafian follicle and formation of corpus luteum.
(b) The corpus luteum secretes large amounts of progesterone and also estrogen which is essential for maintenance of the endometrium. Such an endometrium is necessary for implantation of the fertilised ovum and other events of pregnancy.
(c) Figure d is tertiary follicle which is characterised by a fluid filled cavity called antrum. The theca layer is organised into an inner theca interna and an outer theca externa. It is at this stage the primary oocyte within the tertiary follicle grows in size and completes its first meiotic division. It is an unequal division resulting in the formation of a large haploid secondary oocyte and a tiny first polar body. Figure e -is mature follicle or Graafian follicle. The secondary oocyte forms a new membrane called zona pellucida surrounding it.
(d) Diagram showing mature Graafian follicle
(a) Why is fertilization in an angiosperm referred to as double fertilisation? Mention the ploidy of the cells involved.
(b) Draw a neat labeled sketch of L.S. of an endospermous monocot seed.
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