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31 Cards in this Set
- Front
- Back
Important transitions |
1. Germ layers and tissue development 2. Body symmetry 3. Body cavity 4. Opening of mouth or anus 5. Segmentation 6. Adaptions to environment |
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Germlayers |
Ectoderm - body coverings and nervous system Mesoderm - skeleton and muscles Endoderm - digestive organs and intestines |
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Diploblastic |
Only ectoderm and endoderm |
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Triploblastic |
All three germ layers present |
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1. Tissue development |
Parazoa - sponges, undefined tissues and organs, can disaggregate and aggregate their cells Eumetazoa - all others, 3 germ layers, irreversible differentiation for most cell types |
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2. Body symetry |
Parazoa lack definite symmetry Eumetazoa - radial and bilateral symetry |
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Radial symmetry |
Body parts arranged around central axis Bisected into two equal halves in any 2D plane |
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Bilateral symmetry |
Body has right and left halves that are mirror images Midsagittal plane bisects animal into 2 equal halves |
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Bilaterally symmetrical animals have |
Anterior/ posterior (head-tail) Dorsal/ventral (top-bottom) Left/Right (lateral) Poximal/ distal body appendages (close-far) Cephilization (head development) and greater mobility |
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3. Body cavity |
Acoelomates - no body cavity Pseudocoelomates - body cavity between meso and endo called pseudocoelom Coelomates - within mesoderm, coelom, development of advanced organ systems |
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4. Patterns of development (Bilaterally symmetrical) |
Protostomes - mouth first from blastopore, anus if present develops from elsewhere, flatworms Deuterostomes- anus first from blastopore, mouth later from elsewhere, chordates |
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Protostomes |
Majority coelomate invertebrates Spiral cleavage Determinate development |
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Deuteostomes |
Echinodermata and chordata Radial cleavage Indeterminate development - 8 cell embryo cells are totipotent, can arise to become a whole organism |
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5. Segmentation |
Advantages: 1. Allows redundant organ systems in adults 2. Allows more efficient and flexible movement |
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6. Adaption to environment |
Marine - hospitable, small yolk, external fertilization, no egg protection, larvae Fresh water - less hospitable, moderate yolk, external/internal, egg retained or attached to substrate, sometimes Terrestrial- inhospitable, large yolk, internal, enclosed or internal or laid, insects |
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Gene expression is controlled at many levels, Change in gene expression causes changes in |
cell shape
metabolism activity motility Changes apparent in daughter cells and neighboring cells |
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Autonomous specification |
Due to cytoplasmic components of egg Invertebrates No large scale embryonic cell migration |
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Conditional specification |
Interactions between cells, relative positions are important Vertebrates and few invertebrates ell migrations |
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Syncytial specification |
Insects Interactions between cytoplasmic environment |
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Invagination Involution Ingression Delamination Epiboly |
In-folding Inward movement of outer layer expanding Migration of individual cells to interior Splitting one sheet into two Epithelial sheets spread to enclose deeper layers |
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Urchin cleavage |
Holoblastic isolecital radial cleavage Divisions 1 and 2 are meridional and perpendicular 3 is equatorial and perpendicular |
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Urchin devision 4 |
4 animal pole cells divide meridionally - 8 mesomeres Vegetal - unequal equitorial devision, 4 macro and 4 micromeres 2 large (autonomous) , 2 small micromeres- stop after 5th |
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Fate Animal half Veg 1 Veg 2 Large micromeres Small micromeres |
ectoderm ectoderm and endoderm organs endoderm, coelom, 2nd mesenchyme Larval cytoskeleton Contribute to coelom |
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Blastula formation sea urchin |
After 7th division, blastocoel forms All cells contact fluid inside and hyaline layer Divide, one cell thick, develop cilia, blastula rotates Vegetal cells thicken, animal cells secrete hatching enzyme |
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Gastrulation sea urchin |
Large micromeres extend filopodia, dissociate from monolayer Ingression of primary mesenchyme cells forms larval skeleton Hatch from fertilization envelope Leads to epithelial to mesenchymal cell transition |
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Filopodia |
Formed when primary mesenchyme cells lose affinity for hyaline layer and migrate Senses direction and pattern cues, cluster, travel along blastocoel wall to ventral paracrine factors |
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Vegetal cells invaginate |
caused by change in shape of cells and extracellular matrix 1/4-1/2 of the way, froms archenteron Opening is blastopore |
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Archenteron |
Primitive gut extends dramatically via convergent extension and intercalation Becomes long thin tube |
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Secondary mesenchyme cells |
extend filopodia pulling up archenteron |
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Large micromeres |
Autonomous- not influenced by neighbouring cells Influence other cells When moved to animal pole, they generate endoderm, invagination |
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Beta catenin |
Transcription factor of wnt signaling pathway Sea urchin- found in vegetal, become endoderm and mesoderm accumulation is autonomous, specifies vegetal side Without it cells become ectoderm. In animal will transduce the same reaction |