Cleavage

Question 1

characteristics of cleavage

Answer 1

1. very rapid cell divisions
2. no cell growth before division
3. no net increase in embryo volume
4. cells do not move
5. timing and pattern of division is under control of mom
6. no RNA synthesis from zygotic genome

Question 2

meridional cleavage

Answer 2

along the top/bottom axis

Question 3

equatorial cleavage

Answer 3

cleavage across the middle

Question 4

radial cleavage

Answer 4

radial symmetry around the top-bottom (sea urchin, amphibians)

Question 5

spiral cleavage

Answer 5

when look down from above (molluscs)

Question 6

bilateral cleavage

Answer 6

two sided symmetry (tunicates)

Question 7

discoidal cleavage

Answer 7

cells on top of ball of yolk (birds, reptiles)

Question 8

superficial cleavage

Answer 8

cells around outside (insects)

Question 9

rotational

Answer 9

no simple pattern (mammals, nematodes)

Question 10

amnion

Answer 10

enables embryo to float in fluid environment

Question 11

yolk sac

Answer 11

enables nutrient uptake and development of circulatory system

Question 12

allantois

Answer 12

stores waste products

Question 13

chorion

Answer 13

contains blood vessels and exchanges gases with outside environment

Question 14

shell

Answer 14

casing enables embryo to develop outside of mother

Question 15

placenta

Answer 15

enables embryo to develop inside mother