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) Frederick Griffith worked on Streptococcus pneumoniae to find the process of transformation in the bacteria. When Streptococcus pneumoniae bacteria were grown on a culture plate, some of the bacteria produced smooth shiny colonies (S) due to the presence of polysaccharide coat while others produced rough colonies (R) as they lacked polysaccharide coat.
Griffith then injected mice with this S strain (polysaccharide coat) as well as with R strain bacteria. He found that mice infected with virulent strain died from pneumonia, but mice infected with R strain did not develop pneumonia.
S strain → Injected into mice →Mice died of pneumonia
R strain →Injected into mice →Mice lived
Griffith then killed the S strain bacteria by heating them and injected these heat-killed bacteria into the mice. He observed that heat-killed S strain bacteria did not kill the mice. But when a mixture of heat-killed S and live R bacteria was injected into mice, the mice died.
S strain →injected into mice →Mice lived
S strain (heat-killed) + R strain (live) → Injected into mice → Mice died
It was because the DNA from the heat-killed S strain got transferred into live R strain and transformed the R strain into virulent type which caused pneumonia in the mice and led to their death. This process is called transformation.
(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.
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