Bio 7 Week 13

Front 1

Animal Embryonic Development: common stages that occur in a set order

4 stages

Back 1

fertilization, cleavage, gastrulation, organogenesis

gastrulation + organogenesis = morphogenesis

(morphogenesis = beginning of the shape)

Front 2

cleavage definition:

how long does it continue?

What does it create?

2 types:

Back 2

a series of division without growth --> this continues until the ratio of material in the nucleus to material in the cytoplasm is high (at first the nucleus doesn't have enough material to control the cell)

It creates a blastula

Holoblastic, meroblastic

Front 3

egg poles, what they contain and what the proportions mean for embryonic development

Back 3

animal pole: the "white", vegetal pole: yolk in concentrated here.

Division begins in animal pole and attempts to go all the way through to vegetal. If an animal has little to moderate yolk, it will make it all the way through, but the delay in going through the yolk will eventually cause differences in blastomere sizes (smaller in animal pole) and finally will cause the blastocoel to form entirely in the animal hemisphere. This is exacerbated in eggs with a lot of yolk - cleavage cannot even pass through the yolk and only occurs in animal pole.

Front 4

Holoblastic:

Meroblastic:

Back 4

complete division of the egg (but blastocoel still forms only in animal pole). Happens when there are little to moderate amounts of yolk. Ex: Frogs, Sea Urchins, Mammals

incomplete vision of the egg (cleavage cannot pass through vegetal pole), yolk-rich egg. Ex: reptiles and birds

Front 5

gastrulation:

Back 5

formation of primary germ layers - endoderm, mesoderm, ectoderm make up the gastrula (triploblastic), or just endo and ecto if diploblastic

Front 6

ectoderm forms:

mesoderm forms:

endoderm forms:

Back 6

epidermis, jaw, germ cells, pituitary, nervous

dermis, skeletal, muscle, circulatory, reproductive

epithelial lining of digestive, respiratory, excretory

Front 7

Organogenesis:

In order to do this, you need:

Back 7

reorganization of cells and tissues into rudimentary organs

cell migration, cell signaling, cell differentiation

Front 8

(In Sea Urchins)

fertilization involves 2 blocks against polyspermy:

Back 8

fast block: acrosomal reaction (done by the sperm)

slow block: cortical reaction (done by a chain of events in the egg including granules and vitalize layer)

Front 9

Steps to fast block (acrosomal):

Back 9

1. Jelly coat of egg sends out a chemical to attract sperm

2. acrosome vesicle at tip of sperm releases hydrolytic enzymes which take a part the jelly coat.

3. acrosome has actin filaments it projects out, which bind to receptors on the egg membrane

4. membrane of sperm + egg fuse, causing depolarization --> no other sperm can enter

Front 10

Steps to slow block (cortical)

Back 10

1. Smooth ER releases Ca 2+ into cytosol

2. granules start to release their chemicals in the space between the plasma membrane and the vitalize layer

3. The vitelline layer is pushed away from the plasma membrane

4. no other sperm can get through

5. vitelline layer becomes fertilization envelope

Front 11

fertilization, final steps:

Back 11

nucleus of sperm enters cell, sets off reaction --> Ca2+ spike, egg is activated.

nuclei fuse

Front 12

(In sea urchins)

blastula stages:

blastocoel:

blastomere:

Back 12

zygote --> 4 cell stage --> morula --> early blastula --> later blastula

blastocoel = cavity

blastomere = one of the cells

Front 13

(In sea urchins)

gastrulation:

Back 13

1. mesenchyme cells are large cells surrounded by a matrix that move. most are mesoderm. 2. attach to vegetal plate while at the same time you get an invagination as the vegetal pole folds inwards. 3. mesenchyme cells that are attached to vegetal place send out extensions called filopodia. 4. invagination becomes archenteron. Filopodia are pulling this up to where it will eventually reach the other side and become full digestive tube.

Front 14

fertilization in a frog is...

this means...

Back 14

the same as with a sea urchin

both acrosomal (fast-block) and cortical (slow-block) strategies are used to prevent polyspermy

Front 15

(frog)

cleavage + blastula formation:

(look at slide for picture)

Back 15

division starts at animal pole but the distribution in the cell is different --> organelles/ cells are not distributed evenly.

still goes zygote --> morula --> blastula

cleavage furrow starts at animal pole (should be the same for the sea urchin too)

Front 16

(frog)

gastrulation

(look at slide for picture)

Back 16

1. Dorsal lip forms, cells here push their way to the interior. 2. these cells are attached to other cells (endoderm) that also get pulled along. 3. Through this, they make up the archenteron (blastocoel shrinks). 4. Eventually endoderm plugs blastopore = yolk plug

Front 17

(frog)

neural formation - example of organogenesis

Back 17

formation of neural tube that will later become brain + spinal cord

only care about dorsal ectoderm

1. neural plate thickens 2. With this, it folds on either side. 3. The thickened region starts to fold down. 4. Eventually, it becomes a hollow tube 5. Mesenchyme ectoderm cells remain -- these are neural crest cells - they will form portions of jaw, embryonic skull

Front 18

general vertebrate body plan

please see slides and might want to read book

Back 18

1. Once it's a neural tube, no longer called dorsal hollow... becomes brain and spinal cord

2. notocord = rod = mesoderm

3. somites - masses of mesoderm - vertebra, muscle - form on both sides of notochord - paired

4. coelom - cavities, hold organs, mesoderm

5. archenteron - digestive cavity - endoderm