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) 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.
(a) Double fertilization is a characteristic feature of flowering plants or angiosperms. In the process of double fertilization, out of the two sperm nucleus, one sperm nucleus fuses with the egg nucleus to form an embryo (process is called syngamy) and another fuses with polar nuclei to form endosperm (process is called triple fusion). Since two kinds of fusion; syngamy and triple fusion take place, the process is known as double fertilisation.
Ploidy of the cells involved
|
Cell |
Ploidy |
|
Egg cell |
Haploid |
|
Both Male nuclei |
Haploid |
|
Central cell |
Diploid |
|
Zygote |
Diploid |
|
Endosperm |
Triploid |
(b) L.S of endospermous monocot seed
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