Transcript Embryonic Development of Animals

EMBRYONIC
DEVELOPMENT OF
ANIMALS
Russell
Chapter 50
AP Biology/ Rhodes
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Study of embryology began with Aristotle
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“formation of the embryo”
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Development from single egg cell to multicellular animal
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Growth
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Development of all organ systems
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Following directions of DNA
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3D
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Morphology = the form or shape of an organism
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completed using mitosis
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Cell differentiation = changes in gene expression set cells on a path to establish
specialized structures and functions.
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Morphogenesis = generation of 3D body form
50.1 Mechanisms of Embryo Development
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Egg + sperm = zygote; now a free living organism
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mRNA and proteins in egg are cytoplasmic determinants of growth; mRNA of egg
directs activity until zygote DNA becomes active
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Lots of ribosomes, mitochondria and tubulin, usually pigment
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Development happens on three axes;
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anterior posterior, dorsal ventral and left right
YOLK = nutrients; although placental mammals have relatively little yolk
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Unevenly placed causing polarity
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Slower division at yolk region –
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Vegetal pole; faster divisions, gut and posterior regions (yolk end)
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animal pole; surface and anterior structures – has egg nucleus
Early Development
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Cleavage
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Lots of mitosis
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No change in size or volume
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Many little cells called blastomeres
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in a frog 12 cleavages lead to 4000 cells
Gastrulation
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Now form three major tissue layers or regions
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Cells divide, migrate and rearrange
Organogenesis
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Develops all major organ systems and body organization specific to the species
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Cells divide, migrate and rearrange
CLEAVAGE
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Morula
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Solid ball of blastomeres
Blastula
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Eventually hollow ball called blastula that surrounds
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Fluid filled cavity called blastocoel
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Extensive cell rearranging
[Coelom and coelomate and acoelomates]
Gastrula
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Surface cells move toward center (pocket) in process called gastrulation that forms
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The gastrula or animals “belly”
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Three layers of cells are created “germ layers”
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[germ = germinate or give rise]
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Ectoderm = outer layers; skin/ hair/ feathers/ nerves/ lining of mouth/ glands Table 50.1
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Endoderm= inner layers; linings of all organs
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Mesoderm= middle layers; muscle and bones, blood vessels
DIFFERENTIATION
Gastrulation  Embryo
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Changes in biochemistry, structure, function
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Totipotent - capable of producing all kinds of cells
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Pluripotent – create most types of adult cells
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Multipotent – cells with particular funtions
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Cells still have ALL the DNA, just after specialization (differentiation) they only have
access to parts of the genome that they need/use
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
50.3 Gastrulation  Organogenesis
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Pg. 1126 Neural tube formation
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Neurulation
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Notochord
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Neural plate
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Neural tube
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Somites