BIOL 102 Ch. 32 (An Overview of Animal History)
BIOL 102 Ch. 32 (An Overview of Animal History) BIOL 102 - E01
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This 5 page Class Notes was uploaded by Zach Notetaker on Thursday October 13, 2016. The Class Notes belongs to BIOL 102 - E01 at University of South Carolina taught by Thomas J Reeves (P) in Fall 2015. Since its upload, it has received 3 views. For similar materials see Biological Principles II in Biological Sciences at University of South Carolina.
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Date Created: 10/13/16
BIOL 102 Ch. 32 Lecture Notes: An Overview of Animal Diversity • Kingdom of Consumers: o Most animals are mobile and use traits like strength, speed, toxins, or camoflauge to detect, capture, & eat other organisms § Ex) Chameleon captures insect prey w/ long, sticky, quick-moving tongue • Animals = multicellular heterotrophic eukaryotes w/ tissues that develop from embryonic layers o Nutritional Mode: § Animals are heterotrophs that ingest their food • Cell Structure and Specialization o Animal cells lack cell wa ls o Bodies held together by structural proteins like collag n o Nervous tissues & muscle tissues unique, defining characteristics of anima s o Tissues: groups of similar cells that act as a functional unit • Reproduction & Development: o Most animals reproduce sexually, w/ DIPLOID stage DOMINATING life cycle o After sperm fertilizes egg, zygote, undergoes rapid cell division called clea age o Cleavage leads to formation of multicellular, hollow, blastu a o Blastula undergoes gastrulation, forming a gastrula w/ different layers of embryonic tissues o Most animals have @ least 1 larval stage o Larva = sexually immature and morphologically distinct from the adult; eventually undergoes metamorphosis to become a juvenile § Juvenile resembles an adult, but isn’t yet sexually mat re § Most animals have Hox genes that regulate development of body form • Steps in Origin of Multicellular Animal : o Morphological & molecular evidence points to a group of protists called choanoflagellates as closest living relatives to ani als o Origin of multicellularity requires evolution of new ways for cells to attach and signal to each othe o Molecular analysis has revealed similarities between genes for proetins involved in adherence and attachment in choanoflagellates and animals • Zoologists sometimes categorize animals according to a body plan: set of morphological and developmental traits o Symmetry: § Animals can be categorized according to the symmetry of their bodies, or lack of i 2 § Some animals have radial symmetry, w/ no front and back, or left and right o Two-sided symmetry is called bilateral symmetry § Bilaterally symmetrical animals have: • Dorsal = top side, and a ventral = bottom side • A right and left sid • Anterior = front side and posterior = back ends o Most have sensory equipment, such as brain, concentrated in their anterior end • Radial animals are often sessile or planktonic (drifting or weakly swimming) • Bilateral animals often move actively and have central nervous system • Tissues: o Animal body plans vary according to organization of animal’s tissues o Tissues = collections of specialized cells isolated from other tissues by membranous layers o During development, 3 germ layers give rise to tissues and organs of animal embryo § Ectoderm: germ layer covering embryo’s surface (ecto – outside of) § Endoderm : innermost germ layer and lines the developing digestive tube, called archenteron 3 o Sponges & a few other groups lack true tissues § Diploblastic animals have ectoderm and endoderm • Include cnidarians and a few other groups § Triploblastic animals have intervening mesoderm layer; these include bilaterians • Also include flatworms, arthropods, vertebrates & others • Most triploblastic animals possess a body cavity • A true body cavity is called a coelom and is derived from mesoderm • Coelomates are animals that possess a true coelom • Protostome and Deuterostome Development: o Based on early development, many animals can be categorized as having protostome development or deuterostome development o Cleavage: § Protostome development à cleavage is spiral and determinate § Deuterostome development à cleavage is radial and indeterminate • Indeterminate cleavage, each cell in early stages of cleavage retains capacity to develop into complete embryo o Makes possible identical twins, embryonic stem cells o Coelom (body cavity) Formation: § Protostome development splitting of solid masses of mesoderm forms coelom § Deuterostome development, mesoderm buds from wall of archenteron to form the coelom 4 • Fate of the Blastospore: o Blastospore forms during gastrulation and connects archenteron of exterior of gastrula o Protostome development: blastopore becomes the mouth o Deuterostome development: blastopore becomes anus 5 IMPORTANT POINTS ABOUT RELATIONSHIPS AMONG LIVING ANIMALS REFLECTED IN THEIR PHYOLOGENY 1. All animals share a common ancestor 2. Sponges are basal animals 3. Eumetazoa (“true animals”) is a clade of animals with true tissues 4. Most animal phyla belong to clade Bilateria 5. There are 3 major clades of bilaterian animals, all of which are invertebrates, animals that lack a backbone, except Chordata, which are classified as vertebrates because they have a backbone • Bilaterians divided into 3 clades: o Deuterostomia, Ecdysozoa, Lophotrochozoa o Deuterostomia includes hemichordates (acorn worms), echinoderms (sea stars and relatives) and chordates o Clade includes both vertebrates and invertebrates 5
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