Chapter 32: An Overview of Animal Diversity

Chapter 32: An Overview of Animal Diversity Term Animal Tissues

Cleavage Blastula Gastrulation Larva

Juvenile Hox

Choanoflagellates

Neoproterozoic Era Ediacaran biota Paleozoic Era Cambrian explosion

Definition multicellular, heterotrophic eukaryotes with tissues that develop from embryonic layers groups of cells that have a common structure, function, or both; specialized layers cells isolated from othercollections tisues by of membranous rapid cell division undergone by the zygote after a sperm fertilizes an egg multicellular, hollow; formed from the cleavage undergone by the blastula; forms a gastrula with different layers of embryonic tissues sexually immature and morphologically distinct from the adult; eventually undergoes metamorphosis resembles an adult, but is not yet sexually mature genes that regulate the development of body form; can produce a wide diversity of animal morphology may have resemblance to common ancestors of living animals; protists that are the closest living relatives of animals (1 billion – 542 million years ago) included in the early members of the animal fossil record; dates from 565 to 550 million years ago (542 – 251 million years ago) (535 to 525 million years ago) marks the earliest fossil reappearance of many major groups of living animals Several hypotheses regarding of the Cambrian explosion and declinethe of cause Ediacaran biota:

Mesozoic Era

Cenozoic Era

- New predator-prey relationships - A rise in atmospheric oxygen - The evolution of the Hox gene complex (251 – 65.5 million years ago) coral reefs emerged; ancestors of plesiosaurs were reptiles that returned to the water; dinosaurs were the dominant terrestrial vertebrates; the first mammals emerged; flowering plants and insects diversified (65.5 million years ago to the present) beginning followed mass extinctions of both terrestrial and marine animals which included the large, nonflying dinosaurs and the marine reptiles; mammals increased in size and exploited vacated ecological niches; global climate cooled

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Body plan Radial symmetry Bilateral symmetry Dorsal Ventral Anterior Posterior Cephalization Sessile Ectoderm Endoderm Diploblastic Triploblastic Body cavity Coelom Coelomates Pseudocoelom Pseudocoelomates

Acoelomates Grade

Protostome development Deuterostome development

Blastopore

Eumetazoa Bilaterians

Deuterostomia Ecdysozoans

a set of morphological and developmental traits no front and back, or left and right two-sided symmetry; often move actively and have a central nervous system top bottom head tail development of a head planktonic; drifiting or weakly swimming germ layer covering the embryo’s surface innermost germ layer and lines the developing digestive tube (archenteron) have ectoderm and endoderm; include cnidarians and comb jellies have an intervening mesoderm layer; include all bilaterans possessed by most triploblastic animals a true body cavity; derived from mesoderm animals that possess a true coelom a body cavity derived from mesoderm and endoderm triploblastic animals that possess a pseudocoelom; belong to the same grade as coelomates triploblastic animals that lack a body cavity a group whose members share key biological features; not necessarily a clade. An acestor and all of its descendants cleavage is spiral and determinate; splitting of solid masses of mesoderm forms the coelom Cleavage radial and indeterminate in the earlyis stages of cleavage retains—each the cell capacity to develop into a complete embryo; makes possible identical twins, and embryonic stem cells; mesoderm buds from the wall of the archenteron to form the coelom forms during gastrulation and connects the archenteron to the exterior of the gastrula; becomes the mouth in protosome development; becomes the anus in deuterosome development a clade of animals with true tissues most animal phyla belonging to the clade Bilateria; the morphology-based tree divides bilaterians into deuterostomes and potostomes; molecular studies indicate bilaterian clades Deuterostomia, Ecdysozoa, and Lophotrochozoa chordates and some other phyla shed their exoskeleton through a process called

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Lophopore Trochophore larva

ecdysis feeding structure of some lophotrochozoans distinct developmental stage

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