Chapter 32 An Overview of Animal Diversity Animals are Multicellular Heterotrophic Eukaryotes with tissues that Develop from Embryonic Layers o Cannot construct all required organic molecules must ingest them nby eating Nutritional mode living nonliving organic matter Don t feed by absorption Use enzymes to digest Cell strucutre and specialization o Multicellular eukaryotic o No cell walls Proteins outside the cell membrane collagen o Tissues groups of cells with a commo structure Have muscle and nerve cells Muscles move body Nerves conduct nerve impulses Differenntiates animals from plants and fungi Reproduction and development o Most animals are sexual o Diploid dominnat o Haploid sperm and egg produced by meiosis Small motil sperm fertilizes a larger egg to make a zygote o Cleavage succession of mitotic cell division without cell growht between divisions o Blastula created by cleavage hollow ball of cells o Gastrulation infolding of blastula to make a gastrula Embryonic tissues that will develop into adult boyd bparts will form o Some organisms develop directly into adults o Larvae sexually immature form of an animal that is mrophologically distint from the adult Eats different food and might have a different habitat Undergo metamophasis developmental transformation that turns an animal into a juvenile that resembles adult o All animals have developmental genes to regulate expression of other genes Homeoboxxes Most have hox genes play a role in embryonic development Sponges don t have hox genes Hox gene familiies came from the duplicaiton of homeobox genes Regulate anterior posterior axis and toerh aspects Conserved among animals The History of Animals Spans more than a Half a Billion Years Common ancestor between 800 and 655 mya o Might have been similar to choanoflagellates Neoproterozoic era 1 billion 542 mya o Earliest fossils are of edicaran biota softbodied multicellular eukaryotes o Sponges and cnidarian relatives o Might have evidence of early embryos in fossils Paleozoic era 542 251 mya o Cambrian explosion 535 525 mya wave of diversication First arthropods chordates and echnioderms First skeletons o Predator prey competition increased diversity o Increase in atmospheric oxygen allowed fro higher metabolic rates o Hox genes and other developmental genes develop o Followed by more diversification and extinctions Ordovician Silurian and devonian o Fish emerged as top marine predators o Arthropods moved into terrestrial habitats o Vertebrates on land around 365 mya Amphibians and amniotes survive today Mezozoic era 251 61 5 mya o Phya evolved to spread into new habitats o Water Coral reefs formed new habitats Reptiles back to water o Land Wings Large and small dinosaurs First small mammals Angiosperms and insects underwent diversifiation Cenozoic era 65 5 present o Started with mass extinction Dinosaurs gone o Rise of large mammalian herbivores and predators Animals can be Characterized by Body Plans Animal species morphology is diverse but there is a small bumber of boyd plans Gastrulation control evolved early o Controlled by beta catenin Symmetry o Radial symmetry symmetrical around No front back or left right Sessile living attached to a substrate Planktonic drifting weakly swimming o Bilateral symmetry right and left symmetrical Have front back anterior posterior and top bottom dorsal ventral and right left Move around Tissues collections of specialized cells isolated from other tissues by membranous layers o Embryo becomes layered through gastrulation Germ layers concentric layers that form tissue and organs of the body o Ectoderm layer surrounding embryo Makes outer covering and central nervous system o Endoderm innermost germ layer Lines pouch that forms during gastrulation Gives rise to digestive system and organs like the liver and lungs Body cavities coelom fluid air filled space between digestive tract and outer body wall o Coelomates animals with a true coelom o Pseudocoelomates have cavity formed from mesoderm and endoderm o Acoelomates lack body cavities o Functions of coelom Cushions suspended organs In soft bodied organisms it provides a noncompressable fluid that actlike a skeleton Enables organs to move grow independently of outer body wall Presence of coelom doesn t show evolutionary relationships Protostome and deuterstome development Cleavage Protostome Spiral cleavage splanes of cell division are diagonal to the vertical axis of the embryo Determinate cleavage when development casts deveopmental fate of each embryonic cell early Solid masses of mesoderm split and form coelom Deuterozstome Radial cleavaage plantes of cell division are parallel perpendicular teo the vertical axis of the embryo Indeterminate cleavatge each cell produced by cleagave can become its own embryo Mesoderm budds from archenteron wall and cavity becomes the coelom Mouth is the first to form Anus is the first to form Coelom formation Archenteron blind pouch initially developed by embryos developing a digestive tube Fate of plastopore Blastopore indent formed by gastrulation that leads to the formation of the archenteron In many animals it extends to make 2 openings New views of Animal Phylogeny are Emerging from Molecular Data Phylogenies are constantly changing Points of agreement o Animals share a common ancestor animalia is a monophyletic clade o Sponges are basal animals in a monophyletic clade o Eumetazoa is the clade of organisms with true tissues o Most animals are in the clade bilateria defined by bilateral symmetry and 3 germ layers o Chordates and other phyla are in deutersomma Resolving bliaterian relationships o Molecular phylogenies based on genes Ribosomal hox nuclear and mitochondrial genes
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