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Chapter 32: Intro to Animal Diversity Kingdom Animalia Multi-cellular eukaryotes Heterotrophic – ingest food Structure – no cell walls (use structural proteins in ECM) o Collagen – most abundant Muscle & nerve cells (& tissues) Mostly sexual repro. w/ diploid dom. 35 phyla (9 majors) 3 Eons Archaean (Origin-2.5 bya) o Prokaryotes Proterozoic (2.5 bya-540 mya) o Eukaryotes o Early soft-bodied invertebrates Phanerozoic (540 mya-present) o Complex life forms Animal History Proterozoic Eon o 2.5 bya-540 mya o Ediacaran biota – earliest animals in fossil record From Ediacaran Period 565 to 550 mya 3 Eras in Phanerozoic Eon o Paleozoic Era Cambrian (Period) Explosion (535-525 mya) – earliest fossils of many major animal phyla Arthropods, Chordates, Echinoderms Predator-prey relationships? – drove natural selection Rise in atmospheric oxygen? – allowed higher metabolism & size Evolution of Hox gene complex? – developmental flexibility Ordovician Period (460 mya) – animals land Millipede & centipede (-like) Devonian Period (360 mya) – tetrapods land Lobe-finned fish… o Amphibians o Amniotes – Mammals & Reptiles (& Aves/Birds) Carboniferous Period (350-300 mya) – amphibians dominate Fern forests – today’s coal Permian Period (299-251 mya) – radiation of reptiles Most modern insect groups Permian Mass Extinction (volcanism) o Mesozoic Era – Age of Reptiles (Triassic, Jurassic, & Cretaceous Periods) 251-65.5 mya Corals appear – create huge # of niches & habitat Dinosaurs dominate Reptiles enter water & air Mammals & angiosperms appear Cretaceous Extinction (asteroid) o Cenozoic Era – Age of Mammals 65.5 mya – Present Mammals – adaptive radiation of niches left by reptiles Large herbivores & predators Pollinating insects & birds Human lineage diverged 6-7 mya (species ~195,000 yrs old) Reproduction & Development Fertilization – small, flagellated sperm (n) + large non-motile egg (n) Zygote – single 2n cell Cleavage – rapid mitotic division (1-2n forms 2-2n) w/o cell growth Blastula – ball of cells w/… o Blastocoel – fluid-filled cavity Gastrulation o Blastula folds inwards as cells migrate to fill blastocoel o Gastrula formed Blastopore – opening (hole) Archenteron – primitive gut Germ Layers – embryonic tissue Tissues o Collection of specialized cells isolated from other tissues by membranous layers o Tissues (& organs) made from 3 embryonic germ layers o Germ Layers Ectoderm – outermost layer; becomes Skin & nervous system Endoderm – innermost layer lining archenteron; becomes Digestive tract lining Mesoderm – middle tissue; becomes Muscle, blood, bones Hox Genes o In all animals o Regulate development of body Determine basic structure & orientation of an animal o Hox proteins are transcription factors Bind to certain DNA locations to activate or repress DNA Body Symmetry o No symmetry (e.g. sponge) o Radial symmetry Sessile or planktonic (floating); e.g. Sea Anemone o Bilateral symmetry Move around; e.g. Mammals Body Directions Right & Left sides Dorsal (top) & Ventral (bottom) Anterior (head) & Posterior (tail) Cephalization – sensory organs moved to one end (i.e.development of a head) Body Cavities o Fluid- or air-filled space b/w digestive tract & outer body wall Cushion for organs Organs can grow & move w/o changing skin o 3 types… Coelom – Made only of mesoderm (Coelomate animals) Pseudocoelom – made of mesoderm & endoderm (Pseudocoelomate animals) Acoelom – no body cavity (Acoelomate animals) Development Modes o Deuterostome Cleavage is radial & indeterminate Early cells can make a complete embryo (fraternal twins) Coelom made as archenteron wall (mesoderm) folds to form coelom Blastopore becomes anus (2nd = mouth) o Protostome Cleavage is spiral & determinate Take away a cell = missing body parts Coelom made as solid masses of mesoderm split off & form coelom Blastopore becomes mouth (1st = mouth)