Chapter 54-Animal Development Flashcards Preview

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Flashcards in Chapter 54-Animal Development Deck (23):
1

3 events of fertilization

1. sperm penetration and membrane fusion
2. egg activation
3. fusion of nuclei

2

How does sperm penetration occur

-protective layer of egg eaten away by sperm digestive enzymes located in acrosome
-allows sperm nucleus to enter directly into eggs cytoplasm

3

Egg activation

-dramatic increase in levels of free intracellular Ca2+ ions in egg shortly after sperm makes contact with plasma membrane
-act as second messengers to initiate changes

4

Block to polyspermy

-Rapid transient change in membranc potential
-contical granules remove sperm receptors

5

3 effects of sperm penetration

1. triggers egg to complete meiosis
2. triggers a cytoplasmic rearrangement
3. causes a sharp increase in protein synthesis and metabolic activity in general

6

Fusion of nuclei

haploid sperm and haploid egg nuclei fuse to form diploid nucleus of zygote

7

cell cleavage

-rapid division of zygote into a larger and larger number of smaller and smaller cells forminga solid ball of cells called morula

8

Blastula

forms from morula
-hollow ball of cells

9

Animal pole

portion with no or little yolk

10

vegetal pole

portion with yolk

11

Thing that most affects cleavage pattern of animal embryo

relative amount of nutritive yolk in egg

12

Eggs with little/no yolk

-holoblastic cleavage
-invertebrates, amphibians, mammals

13

Eggs with large amounts of yolk

-meroblastic cleavage
-embryo forms thin cap on yolk

14

Blastocyst composed of..

-trophoblast-outer layer of cells, contributes to placenta
-blastocoel-central fluid filled cavity
-inner cell mass-located at one end, forms developing embryo

15

Gastrulation

-process involving complex series of cell shape changes and cell movements that occurs in blastula
-establishes basic body plan and creates 3 primary germ layers (ectoderm-exterior, mesoderm-middle, endoderm-inner)

16

Gastrulation in mammals

-embryo develops from inner cell mass
-embryo gastrulates as if it was sitting in a ball of yolk

17

Extraembryonic membranes

-amnion, chorion, yolk sac, allantois
-only in adaptation to life on dry land
-nourish and protects developing embryo

18

Amniotic membrane

-encloses amniotic fluid

19

Chorion

-contributes to placenta in mammals

20

Yolk sac

-food source in bird embryos

21

Allantois

-unites with chorion in birds, forming a structure used for gas exchange
-in mammals, contributes blood vessels to the developing umbilical cord

22

organogenesis

-formation of organs in their proper locations
-follows rapidly on heels of gastrulation

23

Notochord

-forms from mesoderm
-region of dorsal ectodermal cells situated above notochord thickens to form the neural plate
-cells of the neural plate fold together to form the neural tube
-will become brain and spinal chord