Development

SRJC, BIO 2.2, Swinstorm. Lecture exam 3

List the key events of animal development

1. gamete formation

2. fertilization

3. cleavage

4. gastrulation

5. organogenesis

6. growth

Gamete Fromation

mature sperm and eggs form

Fertilization

egg and sperm fuse

cleavage

zygote subdivides determinantes partitioned in blastomeres

gastrulation

formation of germ layers

organogenesis

body organs form, cells interact, and differentiate

growth

organs increase in size until the adult body form is attained.

How do eggs prevent polyspermy?

This is prevented when a sperm break through the zone pellucid and then binds to a receptor the cortical granule release and hardens the vitelline layer. This prevents other sperm from entering the jelly coat and binding.

Why does egg type influence cleavage and blastula formation?

The yolk is difficult to divide. This determines the cleavage pattern.

What are the three types of cleavage patterns?

Isolecithal egg, mesolecithal egg, and telolecithal egg

Isolecithal egg

sparse evenly distributed yolk common in mammals which is rotational blastula and echinoderms which is radial blastula formation 

Mesolecithal egg

moderate amount of yolk common in amphibians which is radial blastula formation

Telolecithal egg

dense yolk that is concentrated at one end which are found in birds and reptiles which both have discoidal blastula formation

Determinate cleavage

Fate of cells determined early on in embryo development. if a blastomere is removed blastula may fail

Indeterminant cleavage

fate of cells are not determined early on in embryo development. Blastomeres retain the ability to make a whole embryo

Which type of cleavage leads to twins?

indeterminate cleavage

Deuterostome

blastopore becomes anus first. Mammals

Protostomes

Blastopore becomes mouth first. Echinoderms

What are the three germ layers?

Endoderm, mesoderm, ectoderm

Ectoderm

outer layer, develops epidermis of skin and its derivatives, produces nervous and sensory systems

Mesoderm

Middle layer. Develops skeletal and muscular systems and develops the circulatory and lymphatic systems 

Endoderm

inner layer. Epithelial lining of digestive tract and associated organs. Also the lining of respiratory, excretory and reproductive tracts and ducts. 

neurulation

formation of spinal chord and brain

Describe neurulation

Dorsal membrane forms → notochord signals ectoderm above to form neural plate → neural plate curves inwards forming the neural tube → neural tube becomes DHNC brain and spinal chord → neural crest cells become part of the peripheral nervous system parts of teeth and skull