Short Answer TypeWho was the originator of the theory of Natural Selection ? Explain the evolution of species by this theory.
Write the causative agent and the most important symptom of each of the following diseases :
(i) Whooping cough
(ii) Tuberculosis
(iii) Measles
(iv) Malaria
Differentiate between :
(i) Spontaneous and Induced Mutation.
(ii) Geographical and Reproductive Isolation.
Long Answer TypeTurgor Pressure : Turgor pressure is the pressure of water pushing the plasma membrane against the cell wall of a plant cell. When a plant cell is placed in water, water enters the cell by osmosis, the water exerts pressure on the cell wall.
Significance of Turgidity:
1. It is essential for the growth of the plants.
2. Turgor pressure aids in cell enlargement, consequently in stretching of stems and in keeping leaves erect and fully expanded.
3. Turgidity provides mechanical support to non-woody part of the plant.
4. Loss of turgidity leads to wilting of leaves and drooping of leaves.
5. Opening and closing of stomata are regulated by the turgidity of the guard cells.
6. Leaf movements of many plants are controlled by loss and gain of cell turgor, e.g. Mimosa pudica.
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