Biology 3229F/G Lecture 3: Animal development
24 Feb 2019
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Sperm stimulates zygote (egg) to divide into 2 blastomeres. Blastula has a cavity inside + single layer of tissue. Gastrulation: most important stage in your life, if it doesn"t happen correctly you"ll die. Starts where sperm enters egg, stimulates egg to create a burrow: holoblastic: very little yolk, meroblastic: if your egg is yolky, cleavage stops and is diverted, cleavage doesn"t go through fully. Described as being intermediate or regulative: eg. pluteus larva of a sea urchin. When blastomeres are separated they will develop to a normal (but undersized) pluteus. Described as being determinate or mosaic: eg. trocophore larva of a mollusk. When blastomeres are separated they cannot develop into complete larval form. At the end of the process of cleavage, blastula stage is reached. Blastula: ball of undifferentiated cells, may be hollow (coeloblastula) or solid (stereoblastula) Next stage in development, transforms the one blastula to a two layered gastrula.
