Presentation Transcript
ANIMAL DEVELOPMENT : ANIMAL DEVELOPMENT THE STAGES OF EARLY EMBRYONIC DEVELOPMENT
PREFORMATION vs EPIGENESIS: PREFORMATION vs EPIGENESIS
FERTILIZATION: FERTILIZATION Creates diploid zygote
Triggers embryonic development
The process:
Sperm penetrates egg membranes, head is ingested, nuclei fuse.
Egg’s metabolic machinery is activated, meiosis is completed.
Egg raises barriers to entry of other sperm.
Fertilization membrane lifts off egg--‘slow block to polyspermy’
Acrosomal, Cortical Reactions: Acrosomal, Cortical Reactions
Cortical Reaction: Fertilization Envelope: Cortical Reaction: Fertilization Envelope
After Fertilization: After Fertilization Membrane lifted off zygote
Cleavage Determinants: Cleavage Determinants Distribution of yolk
Even distribution (isolecithal)
Uneven distribution (telolecithal)
Animal pole
Vegetal pole
Holoblastic cleavage (mammals, frogs, sea stars)
Meroblastic cleavage (fish, birds, reptiles)
Deuterostome pattern
Formation of a Blastula: Formation of a Blastula Cell division continues until a hollow ball of cells forms
One cell layer thick
Fluid filled space is a blastocoel
Indentation of blastopore ends this stage
Events of Gastrulation: Events of Gastrulation Three primary germ layers are established.
Basic body plan is established, including the primary body axes.
As a result of the movements of gastrulation, cells are brought into
new positions, allowing them to interact with cells that were
initially not near them. This paves the way for inductive
interactions, which are the hallmark of neurulation and
organogenesis.
4. Archenteron may appear
Radial Cleavage: Radial Cleavage http://www.uleth.ca/bio/bio1020/images/star8.jpg Sea Star
Sea Star Development: Sea Star Development http://www.uleth.ca/bio/bio1020/images/star8.jpg Blastula
Gastrulation: Gastrulation archenteron
Poles, Cleavage: Poles, Cleavage
Frog Cleavage: Frog Cleavage
Frog Holoblastic Cleavage: Frog Holoblastic Cleavage http://www.uleth.ca/bio/bio1020/images/frog12.jpg
Frog Blastula: Frog Blastula http://www.uleth.ca/bio/bio1020/images/frog10.jpg
Gastrulation: Gastrulation http://www.uleth.ca/bio/bio1020/images/frog8.jpg archenteron
Neurulation: Neurulation http://www.uleth.ca/bio/bio1020/images/frog5.jpg
Rate of Cell Division: Rate of Cell Division
EARLY CLEAVAGE 2-64 cells: EARLY CLEAVAGE 2-64 cells
Morula Blastula: Morula Blastula 16-64 cells 128 cells
Blastocoel 256 cells
Development in a Chick Embryo: Development in a Chick Embryo http://www.lawrence.edu/dept/biology/embryoatlas/stage18whole1.jpg
Neurulation in a Chick (24 hr): Neurulation in a Chick (24 hr) http://www.uoguelph.ca/zoology/devobio/24hrchck/24ck2.htm
Chick Embryo 72 hrs: Chick Embryo 72 hrs http://www.uoguelph.ca/zoology/devobio/72hrchck/72ckintr.htm