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Animal Development

Animal Development. Emily Huang, Erin McGrath, Michelle Xu. Review. Cell differentiation Morphogenesis Blastula Gastrulation Cytoplasmic determinants. Fertilization. Sperm + egg  combine to form diploid (zygote)

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Animal Development

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  1. Animal Development Emily Huang, Erin McGrath, Michelle Xu

  2. Review • Cell differentiation • Morphogenesis • Blastula • Gastrulation • Cytoplasmic determinants

  3. Fertilization • Sperm + egg  combine to form diploid (zygote) • Contact of sperm to surface of egg initiates metabolic reactions within egg that trigger onset of embryonic development • Acrosomal Reaction • Cortical Reaction

  4. Fertilization In Different Species Similarities -contact, acrosomal reaction (dig hole into egg), fusion of sperm and egg membranes, complete entry of sperm, cortical reaction blocks other sperm from coming in -sperm cell contains basal body which becomes the centrosome and allows zygote to split Differences Mammal -internal fertilization -eggs coated in follicle cells -fusion doesn’t not occur until after first cell division (12-36 hours) Echinoderm -external fertilization -eggs have a jelly coat -nuclei of sperm and egg fuse immediately -first cell division occurs 90 minutes after fusion

  5. After Fertilization… • …embryonic development proceeds through cleavage, gastrulation, and organogenesis. • Stage 1: cleavage  cell division creates a hollow ball of cells (blastula) from the zygote • Stage 2: gastrulation  produces 3 layered embryo (gastrula) • Stage 3: organogenesis  generates rudimentary organs from which adult structures grow

  6. Cleavage • Blastomeres: smaller cells that result from cleavage, each with its own nucleus • First 5-7 divisions form a cluster of cells known as the morula • Blastocoel: fluid filled cavity that begins to form within the morula • Yolk: stored nutrients, most concentrated toward one pole, the vegetal poleand decreases toward the animal pole • Afterwards, gastrulation occurs

  7. Gastrulation • Dramatic rearrangement! • Forms primitive gut • Driven by changes in cell motility, cell shape, and cellular adhesion to other cells and e.c. matrices • 3 layers produced- collectively the gastrula • Germ layers: ecto, meso, endo Sea Urchins: Frogs: Chicks:

  8. Germ Layer Fun ENDODERM: -epithelial lining of digestive tract and respiratory system -lining of urethra, urinary bladder, repro. system -liver, pancreas, thymus, thyroid ECTODERM: -skin (sweat glands, hair follicles) -sensory receptors in epidermis -cornea, lens of eye -nervous system -tooth enamel MESODERM: -skeletal system -muscular system -excretory system -circulatory and lymphatic systems -reproductive system -dermis of skin

  9. Organogenesis When the three germ layers begin to develop into organs Frog Chick

  10. Development Adaptations of Amniotes • Reptiles, birds, and mammals are called amniotes. • All vertebrate embryos require aqueous environment, so animals use fluid filled eggs or uteri

  11. Extraembryonic Membrane • Present in mammals, birds and reptiles. • In birds and reptiles: germ layers develop into • Amnion- contains the fluid and fetus • Yolk sac, chorion, and allantois • Allantois is a disposal sac for waste • Yolk sac expands over yolk, stockpile of nutrients • Exchange gases between embryo and surroundings • These structures provide “life support system” • Mammals have the same structures, only we have a uterus instead of an egg to contain them

  12. THEM (chicken) US

  13. Morphogenesis • Cytoskeletons in animals cells allow them to “crawl” from place to place in all developing animals. • Cell crawling changes the shape of the developing animal by extending or contracting- convergent extension

  14. What affects developmental fate? • Cytoplasmic determinants  cell differentiation • Interactions among cells causes changes in gene expression  “induction”

  15. Limb Formation and Spatial Organization • Inductive signals play a major role in pattern formation • Positional information: molecules that direct a cell to its correct location in the body • In all animals with limbs: apical ectodermal ridge (AER), zone of polarizing activity (ZPA) • They are major limb bud organizers

  16. apical ectodermal ridge (AER)- a thick ridge of ectoderm at the tip of a bud of a limb, determines growth of the limb • zone of polarizing activity (ZPA)- sprouts from the mesoderm, forms the digits • ZPA excretes a protein growth factor called SONIC HEDGEHOG!!!!!!!!!!!!!!

  17. THE END <3

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