development I

Question 1

what are the key stages in animal development

Answer 1

1. gamete formation: oogenesis and spermatogenesis
2. fertilization: gamete nuclei fuse
3. cleavage: zygote divides into many smaller cells
4. gastrulation: tissue layers form
5. organogenesis: cells differentiate, organs form
6. growth: organism gets bigger

Question 2

what is the first step in fertilization?

Answer 2

sperm penetrates a jelly layer around egg

Question 3

second step in fertilization

Answer 3

sperm contacts the vitelline envelope

Question 4

third step in fertilization

Answer 4

proteins on the acrosomal process bind to species-specific receptors on the vitelline envelope of the egg

Question 5

4 (fast block)

Answer 5

electrical potential change rapidly spreads across the membrane to prevent the entry of any other sperm; egg becomes positively charged which repels any other sperm

Question 6

what follows fast block?

Answer 6

slow block: cortical granules release contacts between the membrane and vitelline, creates an osmotic gradient

Question 7

during slow block: where does the water rush into?

Answer 7

water rushes into space, elevates the envelope, and lifts away all the bound except one sperm that has successfully fused with the egg plasma membrane.

Question 8

what happens to sperm after fusion

Answer 8

sperm loses its flagellum; nuclear envelope breaks apart to allow chromatin to expand

Question 9

male pronucleus and migrates inward to contact the ___

Answer 9

female pronucleus

Question 10

cleavage

Answer 10

sequence of miotic divisions

Question 11

what is cleavage affected by

Answer 11

-quantity and distribution of yolk present
-genes that control the symmetry of cleavage
- arrangement of cytoplasm

Question 12

holoblastic cleavage

Answer 12

cleavage furrow extends completely through the egg

Question 13

meroblastic

Answer 13

cleavage furrow does not cut through the yolk at all

Question 14

superficial cleavage

Answer 14

restricts cleavage to the cytoplasmic rim of the egg

Question 15

very little yolk distributed evenly in the cytoplasm, holoblastic

Answer 15

isolecithal egg

Question 16

mesolecithal egg

Answer 16

a moderate amount of yolk concentrated in the vegetal pole; holoblastic

Question 17

centrolecithal egg

Answer 17

much yolk concentrated in the center; meroblastic, superficial

Question 18

telolecithal

Answer 18

much yolk concentrated at the vegetal pole; meroblastic

Question 19

blastula

Answer 19

cluster of cells after continuous cleavage

Question 20

blastoderm

Answer 20

single sheet of cell layers

Question 21

blastocoel

Answer 21

fluid-filled cavity

Question 22

gastrulation:

Answer 22

converts blastula into 2-3 layer embyro

Question 23

diploblastic

Answer 23

two germ layers: ectoderm,endoderm

Question 24

triploblastic

Answer 24

three germ layers; ectoderm, endoderm, mesoderm

Question 25

gastrocoel

Answer 25

forms new internal cavity

Question 26

opening into second cavity

Answer 26

blastopore

Question 27

blind or incomplete gut

Answer 27

embryonic gut opens only into the blastopore

Question 28

complete pathway from the mouth to the anus

Answer 28

complete gut

Question 29

protostomes

Answer 29

blastopore becomes the mouth

Question 30

blastopore becomes the anus

Answer 30

deuterostomes

Question 31

body cavity filled with fluid surrounded by the mesoderm, acts as a hydrostatic skeleton, resisting external pressure

Answer 31

coelom

Question 32

allows internal organs to move and grow and acts as a protective cushion for internal organs

Answer 32

coelom