Which one of the following statements is correct for secondary succession ?
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(a) It begins on a bare rock (b) It occurs on a deforested site (c) It follows primary succession (d) […]
The population of an insect species shows an explosive increase in numbers during rainy season followed by its disappearance at the end of the season. What does this show?
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(a) The food […]
In the case of peppered moth (Biston betularia) the black – coloured form became dominant over the light- coloured form in England during industrial revolution. This is an example of:
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(a) appearance […]
A biologist studied the population of rats in a barn. He found that the average natality was 250, average mortality 240, immigration 20 and emigration 30. The net increase in population is :
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During the transmission of nerve impulse through a nerve fibre, the potential on the inner side of the plasma membrane has which type of electric change?
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(a) First positive, then engative and […]
Which one of the following is the correct difference between Rod Cells and Cone Cells of our retina?
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(a) Visual acuity: High Low (b) Visual pigment: Iodopsin Rhodpsin (c) Overall function: Vision […]
Cornea transplant in humans is almost never rejected. This is because
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(a) Its cells are least penetrable by bacteria (b) it has no blood supply (c) it is composed of enucleated cells (d) […]
Which of the following is an example of negative feedback loop in humans?
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(a) Secretion of tears after falling of sand particles into the eye. (b) Salication of mouth at the sight […]
During the propagation of a nerve impulse, the action potential results from the movement of?
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(a) K⁺ ions from extracellular fluid to intracellular fluid (b) Na⁺ ions from intracellular fluid to extracellular fluid […]
When a neuron is in resting state I not conducting any impulse, the axonal membrane is:
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(a) comparatively more permeable to Na⁺ ions and nearly impermeable to K⁺ ions (b) equally permeable to […]
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