12. Please provide correct solution. Preferentially done by hand or on paper. 49
ID: 50532 • Letter: 1
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12. Please provide correct solution. Preferentially done by hand or on paper. 49. Which of the following embryos shows the most dramatic form of meroblastic cleavage? a. Sea urchin. b. Frog. c. Chicken. d. Human. 50. In amniotes, which extraembryonic membrane disposes of nitrogenous wastes? a. Amnion. b. Chorion. c. Allantois. d. Yolk sac. 51. Which of the following, if any, is an example of positive feedback? Select E if none are examples. a. b. c. d. e. Estrogen and progesterone (luteal phase) An action potential. Resting membrane potential. Testosterone feedback on the hypothalamus None of the above are examples of positive feedback. 52. Which of the following, if any, is an example of an animal with a gastrovascular cavity? Select E if none are examples. a. b. c. d. e. Earthworm Hydra Nematode (round worm) Humans None of the above organisms have a gastrovascular cavityExplanation / Answer
49. b. frog
Meroblastic cleavage of the embryo (only a part of the cleavage occurs in eggs those are filled with yolk). Some animals including reptiles, amphibians and birds exhibit meroblastic cleavage. Frog is an amphebian.
50. c. Allantoin
In amniotes, allantoin is an extraembryonic membrane that stores and disposes of nitrogenous wastes.
51. c. Action potential.
Action potential is an example of positive feedback mechanism. In this, any stimulus causes opening of slow sodium channels, which further trigger the opening of fast sodium channels to establish an action potential.
52. b. hydra.
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