Review of Bio 102 Midterm 2

Animal Development 1

A single cell can give rise to the function of an entire organism

Stages the cell go to:

1- Cell division

2- Morphogenesis

3- Differentiation: when you can physically see the changes.

*

* Major Stages of Development:

* Even before fertilization the eggs of different species have polarity.

1- Fertilization

* Contributes further to polarity

* Establishes site of Grey Crescent (Future Organizer region)

2- Cleavage

* Several rounds of cell division without cell growth

* Repackages cytoplasm

3- Blastula

* Formation of central fluid cavity

4- Gastrulation

* Differentiation of cells into 3 layers.

* Formation of Axes.

* Involution of blastopore:

* Opening that will become the gut

* Dorsal Lip and spirnann’s organizer

* In Mammals: formation of the primitive streak

5- Organogenesis

* Neurulation

* Ectodermal neural plate overlies mesoderm

* Folds to become a neural tube

1- Sea Urchin Fertilization:

* Similar to amphibian fertilization, in water.

* See urchin egg is protected by 2 layers:

* Jelly layer

* Protein vitelline envelope

* Sperm must penetrate both to reach the egg plasma membrane.

* Many sperms attach to the vitelline envelope but only one penetrates the plasma membrane and fertilizes it.

* The sperm has mitochondoria to keep it moving.

* The male also donates centrioles in addition to the sperm

* The process :

1- The acrosomal Reaction: the acrosomal membrane In the sperm breaks down and releases digestive enzymes that digest a path for the sperm in the egg’s jelly layer.

2- Fast block of polyspermy: Polymerization of Actin creates the acrsomal process, which contacts the eggs plasma membrane triggers the fast block by changing the electric charge on the membrane ( from negative to positive).

a. Normally, insde of the cell is negative and outside in positive to...