1. Embryonic Development of Animals
Russell
Chapter 50
AP Biology/ Rhodes

2. Study of embryology began with Aristotle
“formation of the embryo”
Development from single egg cell to multicellular animal
Growth
Development of all organ systems
Following directions of DNA 3D
Morphology = the form or shape of an organism
completed using mitosis
Cell differentiation = changes in gene expression set cells on a path to establish specialized structures and functions.
Morphogenesis = generation of 3D body form

3. 50.1 Mechanisms of Embryo Development
Egg + sperm = zygote; now a free living organism
mRNA and proteins in egg are cytoplasmic determinants of growth; mRNA of egg directs activity until zygote DNA becomes active
Lots of ribosomes, mitochondria and tubulin, usually pigment
Development happens on three axes;
anterior posterior, dorsal ventral and left right
YOLK = nutrients; although placental mammals have relatively little yolk
Unevenly placed causing polarity
Slower division at yolk region –
Vegetal pole; faster divisions, gut and posterior regions (yolk end)
animal pole; surface and anterior structures – has egg nucleus

4. Early Development Cleavage Gastrulation Organogenesis Lots of mitosis
No change in size or volume
Many little cells called blastomeres
in a frog 12 cleavages lead to 4000 cells
Gastrulation
Now form three major tissue layers or regions
Cells divide, migrate and rearrange
Organogenesis
Develops all major organ systems and body organization specific to the species

5. CLEAVAGE Morula Blastula Gastrula Solid ball of blastomeres
Eventually hollow ball called blastula that surrounds
Fluid filled cavity called blastocoel [Coelom and coelomate and acoelomates]
Extensive cell rearranging
Gastrula
Surface cells move toward center (pocket) in process called gastrulation that forms
The gastrula or animals “belly”
Three layers of cells are created “germ layers” [germ = germinate or give rise]
Ectoderm = outer layers; skin/ hair/ feathers/ nerves/ lining of mouth/ glands Table 50.1
Endoderm= inner layers; linings of all organs
Mesoderm= middle layers; muscle and bones, blood vessels
DIFFERENTIATION

6. Gastrulation  Embryo Changes in biochemistry, structure, function
Totipotent - capable of producing all kinds of cells
Pluripotent – create most types of adult cells
Multipotent – cells with particular funtions
Cells still have ALL the DNA, just after specialization (differentiation) they only have access to parts of the genome that they need/use

7. Development Processes
1. Mitosis
2. Cell migrations
3. Cell adhesions – make and break connections between cells  tissues
4. Induction – influences by surrounding cells
5. Determination – must become a cell type because of induction
6. Differentiation – cell specific development (structures and functions)
7. Apoptosis – programmed cell death…. Between fingers

8. 50.3 Gastrulation  Organogenesis
Pg Neural tube formation
Neurulation
Notochord
Neural plate
Neural tube
Somites