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23 Cards in this Set
- Front
- Back
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What is morphogenesis? |
The process by which the embryo changes shape to establish the body plan |
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Two tissue types |
Parazoa (sponges) – no true tissues or organs: just collections of cells Eumetazoa (all other animals) – true tissues and organs |
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Two body symmetry types for eumetazoa |
Radiata (radially symmetrical)(two embryonic tissues types) Bilateria (bilaterally symmetrical)(three embryonic tissue types) |
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Two body cavity (coelom) types for bilateria |
Acoelomate (no body cavity) Pseudocoelomate (a ‘false’ body cavity) Coelomate (a true body cavity) |
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Modes of development for bilateria |
Protostome Deuterostome (these are all coelomate) |
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3 types of symmetry |
Asymmetry (only Parazoa) Eumetazoa: Radial Bilateral |
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What are the features of bileterians |
A dorsal (top) side & a ventral (bottom) side A right and left side Anterior (head) and posterior (tail) ends Cephalisation - the development of a head |
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What are the germ layers in embryos? |
Endoderm Ectoderm Mesoderm |
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Diploblasts and triploblasts |
Theembryos of diploblastscontain ectoderm and endoderm Radiata are diploblasts Theembryos of triploblastscontain ectoderm, endoderm and mesoderm Bilateral are triploblasts |
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What do the different germ layers produce in development? |
Endoderm - produces the gut and its associated organs Mesoderm - produces muscles and other organs (such as circulatory system) Ectoderm - produces outersurface of the animal (for example skin) & nervous system in some animals |
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Why are all radiata acoelomates (lacking central cavity)? |
They are diploblasts and so lack mesodermal tissue |
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Acoelomates |
EG: flatworms; lack abody cavity between the digestive tract and outer body wall |
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Pseudo-coelomates |
Have a body cavity only partially lined by tissue derived from mesoderm |
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Coelomates |
A true coelom: a body cavity completely lined by tissue derived from mesoderm |
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Protostome & deuterostome |
In protostome development: the mouth forms first and theanus forms second In deuterostome development: the mouth forms second and theanus forms first |
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Differences in cell division after fertilisation between protostomes and deuterostomes |
Thebasic pattern of cell cleavage differs in protostomes and deuterostomes. Cleavagein protostomes is “spiral” Cleavagein deuterostomes is“radial” |
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When does the coelom form |
Duringa developmental period called “gastrulation”. |
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What is gastrulation? |
A highly complex process where the ball-shaped blastula is reorganised toform a complex multi-layered structure |
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Frog gastrulation |
Invagination: a sheet of cells (called an epithelial sheet) bends inward. Ingression: individual cells leave an epithelial sheet and become freely migrating mesenchyme cells. Involution: an epithelial sheet rolls inward to form an underlying layer.
Epiboly: a sheet of cells spreads by thinning. Intercalation: rows of cells move between one another, creating an array of cells that is longer (in one or more dimensions) but thinner. Convergent Extension: rows of cells intercalate, but the intercalation is highly directional. |
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Frog gastrulation summary |
Invaginationat equatorial region to form blastopore Involutionof mesoderm and endoderm through the blastopore Spreadingout of ectoderm from animal pole to enclose embryo |
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What is organogenesis? |
Cellularspecialisation in different regions of the 3 germ layers and interactionsbetween the tissues lead to organ formation Elementsof the nervous system are among the first organs to develop in chordates |
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If a species has a notochord, it is, by definition, a chordate. |
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What is neuralation? |
Folding process in vertebrate embryos, which includes the transformation of the neural plate into the neural tube |
