Download Ch. 47*Animal Development - Kirchner-WHS

Ch. 47—Animal Development
Fertilization
Fertilization
Fertilization
Fertilization
Once fertilization is complete
Animal Development
• Cleavage—rapid mitotic
cell division into smaller
cells—blastomeres
• Solid ball of cells—
morula
• Blastula produced when
a cavity called blastocoel
forms
• Gastrulation—
rearrangement of cells
into 3 germ layers
blastomeres
Morula
(solid ball
of cells)
Blastocyst
• Blastula stage of
mammalian embryos
• Trophoblast layer
enclosing the
blastocoel
– Chorion (outer
embryonic layer)
Blastocyst develops into gastrula
Gastrulation
• Cells rearrange and fold inward at the blastopore to
form a gastrula with three-germ layers:
– Ectoderm (skin, nails, teeth)
– Mesoderm (skeletal, muscular, excretory, circulatory,
reproductive systems; blood, bone, and muscle)
– Endoderm (epithelial lining of digestive, respiratory,
excretory tracts; liver, pancreas)
Organogenesis
• Development of 3 germ
layers into the beginnings
of organs
– Notochord—stiff dorsal
skeletal rod (from
mesoderm)
– Neural plate—will become
brain and spinal cord (from
ectoderm)
– Somites—blocks of
mesoderm arranged along
notochord; sign of
segmentation
Amniotes
•
•
•
•
Amnion—fluid filled cavity; protects embryo
Allantois—disposal sac
Chorion—exchange gases
Yolk sac—provides nutrients
Eutherian mammals