Development AxolotlChicken. Gametogenesis The formation of gametes occurs within the gonads (ovaries...
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Transcript of Development AxolotlChicken. Gametogenesis The formation of gametes occurs within the gonads (ovaries...
Development
Axolotl Chicken
GametogenesisThe formation of gametes occurs within the gonads (ovaries and testes.)
Spermatogonia and oogonia undergo mitosis to produce primary spermatocytes and oocytes.
Primary gametocytes undergo meiosis twice to produce four spermatozoa or a single ovum.
Fertilization
The haploid egg and haploid sperm unite resulting in a diploid zygote.
Cell Cleavage Rapid divisions increase
cell numbers with no increase in size
1st Cleavage = 2 cells 2nd Cleavage = 4 cells 3rd Cleavage = 8 cells 4th Cleavage = 16 cells 5th Cleavage = 32 cells
(morula) Hollow ball of cells
(blastula) forms with a fluid filled cavity in the center (blastocoel)
Gastrulation
Invagination (denting inward) and involution (rolling inward) of cells producing blastopore.
The 3 primary germ layers are established: EctodermMesodermEndoderm
Gastrulation in Aquatic Vertebrates
Ectoderm formed as cells from the animal pole surround larger yolk cells which form the endoderm.
Mesoderm formed at an involuting dorsal lip at the blastopore (see models)
Gastrulation in reptiles, birds, and mammals
The cells of the blastodisc which are adjacent to the yolk become endoderm.
Mesoderm is formed at the involuting primitive streak (an elongated blastopore) on the dorsal surface of the blastodisc.
Germ Layer Development
EctodermNervous system, cornea and lens of eye, epidermis of
skin, epithelial lining of mouth and rectum
MesodermCirculatory system, segmented muscles, skeleton,
kidney, gonads, outer covering of internal organs, lining of thoracic and abdominal cavities
EndodermPharynx, liver, pancreas, lining of digestive tract,
lining of respiratory tract
Cleavage (2 cells) Cleavage (4 cells) Blastula Early Gastrula
Late Gastrula Early Neurula Early Tail Bud Late Tail Bud
Axolotl Development
Chick Embryo Development
4 day embryo removed from the egg:
http://www.youtube.com/watch?v=Bzvpa1SaGgY
9 day embryo inside egg:http://www.youtube.com/watch?
v=Tjeq58oLdVk
Fertilized egg to a baby chickhttp://www.youtube.com/watch?v=kwGkkOeoLTg&feature=related
Candling: Interpreting what you see…
Freshly laid egg (air pocket and yolk are visible): if it is over a week
old it is not fertile
Fertile egg at approximately 5 days old. Notice the faint blood vessels.
Opaque egg: the chick has developed to the point that you
can’t see through the egg at all.
This egg is opaque, but it has a large, off-center air pocket. It could contain a dead-in-shell chick, or it
could be an old rotten egg.
Chicken Egg Candling
• Unfertilized Chicken Egg • Fertilized Chicken Egg
Today’s Tasks• Station 1: Model amphibian development
– Sketch 1 stage & label layers & other identifiable structures• Station 2: Preserved and live frog embryos
– 1 sketch any stage• Label developmental stage and identifiable structures
– Discuss questions in your discussion• Station 3-4: Live axolotl, frog & killifish embryos
– 2 sketches of axolotls at different developmental stages– 2 sketches of killifish at different developmental stages
• Label developmental stages, and any of the following you can find: yolk, head, tail, dorsal/ ventral sides, eyes, blood vessels, heart
– Discuss questions in your discussion• Station 5: Chick Embryos
– 2 sketches at different developmental stages• Refer to description card to label all identifiable parts
– Discuss questions in your discussion