Presentation on theme: "AN INTRODUCTION TO ANIMAL DIVERSITY"— Presentation transcript:
1 AN INTRODUCTION TO ANIMAL DIVERSITY CHAPTER 32AN INTRODUCTION TO ANIMAL DIVERSITY
2 I. Concept 32.1: What is an Animal? 95% are invertebratesMulticellularEukaryoticHeterotrophic (ingestive)Lack cell wallsMost are mobileDiploid with haploid gametesSexual reproduction (zygote blastula gastrula)
4 9. Carbohydrates stored as glycogen 10. Some produce larva which undergo metamorphosis11. Specialized systems12. Two unique types of tissue: nervous tissue and muscle tissue13. Share the unique homeobox-containing family of regulatory genes know as Hox genesHox genes play an important role in development of animal embryos
5 II. Concept 32.2: Animal History A. Common Ancestor1. May have resembled modern choanoflagellates 2. Choanoflagellates are protists that are the closest living relatives of animals and were probably a colonial, flagellated protist.Such a colony is about 0.02mm high.
7 III. Concept 32.3: Body Plans A. PhylogenyDefine as the evolutionary history of speciesBased on general features of morphology and developmentEach major branch represents a grade, (group of animal species that share the same level of organizational complexity)A grade is not necessarily a clade or monophyletic group.
9 B. Major Branches of the Animal Kingdom 1. Subkingdom ParazoaSimple anatomy (lack true tissues)Phylum Porifera2. Subkingdom EumetazoaTrue tissuesAll other phyla
10 C. Body PlansA body plan is a set of morphological and developmental traits1.SymmetryAnimals can be categorized by body symmetry or the lack of ita. Radial symmetry (Radiata)-Characterized by a body shaped like a pie or barrel, with many equal parts radiating outward like spokes of a wheel-have oral and aboral sides but no front, back, left, or right surfaces
11 b. Bilateral symmetry (Bilateria) -Characterized by a body form with a central longitudinal plane dividing the body into two equal but opposite halves-A dorsal (top) and ventral (bottom) sides-Anterior (head) and posterior (tail) ends-Left and right sides-Exhibit cephalization (concentration of nerves and sense organs on anterior end)
13 2. Tissuesa. Tissues are collections of specialized cells isolated from other tissues by membranous layersb. During gastrulation (downward and inward movement of cells of blastula), three germ layers form which give rise to the tissues and organs of the animal embryo
14 Tissues develop from two germ layers (ectoderm or endoderm) c. DiploblasticTissues develop from two germ layers (ectoderm or endoderm)d. TriploblasticTissues develop from three germ layers:Ectoderm is the outer most germ layer which develops into outer layer and central nervous systemEndoderm is the inner most germ layer and lines the developing digestive tube called the archenteronMesoderm is the middle layer which is located between ectoderm and endodermIncludes all bilaterians
16 3. Body Cavity (Coelom)Defined as a fluid- or air-filled space separating the digestive tract from the outer body walla. AcoelomateNo body cavity between digestive tract and outer body wallArea filled with cellsPhylum Platyhelminthes
20 c. Coelomate (true body cavity) Body cavity lined with mesodermMesenteries connect outer and inner mesoderm and suspend internal organsPhyla: Echinodermata ArthropodaMollusca ChordataAnnelidaFunctions of the body cavity1. Fluid cushions the suspended organs, helping to prevent internal injury2. In soft-bodied coelomates, functions as a hydrostatic skeleton against which muscles can work3. Enables internal organs to grow and move independently of the other body wall
23 4. Development--Protostomia vs. Deuterostomia 2 evolutionary lines in coelomatesDiffer in cleavage, fate of blastopore, and coelom formationProtostomes—mollusks, annelids, arthropodsDeuterostomes—echinoderms, chordates
24 a. CleavageProtostomesSpiral Cleavage—cleavage diagonal to the embryo’s vertical axisDeuterostomesRadial Cleavage—cleavage either parallel or perpendicular to embryo’s vertical axis
25 b. Determination ProtostomesDeterminate Cleavage—developmental fate of each cell determined very early-A cell from 4-cell stage will not develop fully DeuterostomesIndeterminate Cleavage—early cells retain ability to develop into complete embryo if isolated from other cells-Makes possible identical twins and embryonic stem cells
27 c. Coelom FormationProtostomesSchizocoelous—the splitting of solid masses of mesoderm forms the coelomDeuterostomesEnterocoelous—the mesoderm buds from the wall of the archenteron to form the coelom
36 A. Points of AgreementAll animals share a common ancestorSponges are basal animalsEumetazoa is a clade of animals (eumetazoans) with true tissuesMost animals phyla belong to the clade Bilateria and are called bilateriansChordates and some other phyla belong to the clade Deuterostomia
37 B. Progress in resolving Bilaterian Relationships 1. The morphology-based tree divides bilaterians into two clades: deuterostomes and protostomes 2. In contrast, recent molecular studies indicate three bilaterian clades: Deuterostomia, Ecdysozoa, and Lophotrochozoa a. Ecdysozoans shed their exoskeletons through a process called ecdysis (Arthropoda and Nematoda) b. Some lophotrochozoans have a feeding structure called a lophophore ( Mollusca, Annelida, Rotifera, Platyhelminthes) c. Other phyla go through a distinct developmental stage called the trochophore larva(Mollusca and Annelida)
42 You should now be able to: List the characteristics that combine to define animalsDistinguish between the following pairs or sets of terms: radial and bilateral symmetry; grade and clade of animal taxa; diploblastic and triploblastic; spiral and radial cleavage; determinate and indeterminate cleavage; acoelomate, pseudocoelomate, and coelomate gradesCompare the developmental differences between protostomes and deuterostomesCompare the alternate relationships of annelids and arthropods presented by two different proposed phylogenetic treesDistinguish between ecdysozoans and lophotrochozoans
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