BIOL 100 Lecture Notes - Lecture 21: Gastrulation, Eumetazoa, Body Cavity
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Animals are multicellular eukaryotic heterotrophs that ingest their food. Discuss how different groups of animals are classified. Heterotrophs- gain organic material and food from somewhere else. Ingestion- they eat, don t absorb food from skin. No cell walls- they are held by extracellular matrix of proteins (collagen) Most animals are eumetazoa and have true tissues: cells perform specific function. Embryonic ball of cells fold in on itself: gastrula. Gastrula goes in three ways: endoderm, ectoderm, mesoderm. Some bilaterally symmetrical animals lack body cavities all together. Radial symmetry- any plane passing thru the mouth and opposite end of body will be a mirror image (5 ways a starfish can be split) Identify the three germ layers (embryonic tissues) and their fates. Distinguish between direct and indirect development (which involves metamorphosis?) Direct development- baby resembles an adult in the future or present. Indirect development- the baby needs to go thru an extra step (metamorphosis) larva to become adult.