Exam 3 Study Notes

Exam 3 Study Notes - Exam 3 Study Notes: 31 - 34, 50 52...

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Exam 3 Study Notes: 31 - 34, 50 – 52 Animals are a monophyletic group of multicellular eukaryotes that is particularly species-rich and morphologically diverse. = About 34 phyla, maybe 10 million or more species Most major animal clades appear 500-550 MYA ( the Cambrian era) Their closest living relatives are the choanoflagellates, a group of protists, which are not, however, free-living organisms. Animals are key consumers and humans depend on them (especially deuterostomes) for transportation, power, and food. 5 Main Ways Animals Feed: 1) Suspension feeding/Filter feeding = capturing food by filtering out particles suspended in water or air 2) Deposit feeding = eating one’s way through a substrate 3) Herbivory = harvesting algae or plant tissues 4) Predation = either waiting for or stalking one’s prey 5) Parasitism = parasites are generally smaller than victims and harvest nutrients without causing death a. endoparasites = live inside hosts b. ectoparasites = live outside hosts The three main functions of locomotion in adult animals are escape from predators, finding food, and finding a mate. Major groups of animals are defined by the design and construction of their basic body plan, which differs in the number of tissues observed in embryos, symmetry, the presence or absence of a body cavity, and the way in which early events in embryonic development proceed. SPONGES (Porifera) are the only asymmetric animals without tissues (cells organized into tightly integrated structural and functional units). They are suspension feeders, are benthic (live at the bottom of their aquatic environment, and can reproduce via fragmentation. They are also the most ancient animal group living today. CNIDARIANS and CTENOPHORES have radial symmetry and are diploblasts (they have two embryonic tissues). Their embryos have only the ectoderm and endoderm germ layers.
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Cnidarians have a cnidocyte - a specialized cell for prey capture that ejects a barb coated in toxins, and have a life cycle with both a polyp and medusa form. The vast majority of animals have bilateral symmetry (are symmetrical across one plane and face their environment in one direction), are triploblasts (have three embryonic tissues), and a coelom (an internal fluid-filled cavity) —design features which lend themselves to a “tube within a tube” body plan. Cephalization is the evolution of an anterior region for feeding, sensing the environment, and information processing. Together with bilateral symmetry, unidirectional movement became possible. Animals have a characteristic pattern of development: zygote, cleavage, blastula, gastrula with blastophore Triploblastic embryos have three germ layers: the endoderm (digestive tract), ectoderm (skin and nervous system), and mesoderm —which gives rise to most organs and bones The coelom is not present in diploblasts; they are acoelomates . Most triploblasts are coelomates—and their coelom forms from within the mesoderm. The “tube within a tube” body plan is built either by the
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Exam 3 Study Notes - Exam 3 Study Notes: 31 - 34, 50 52...

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