1 Overview: Welcome to Your KingdomThe animal kingdom extends far beyond humans and other animals we may encounter Video: Coral Reef

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3 Several characteristics, taken together, sufficiently define the groupConcept 32.1: Animal are multicellular, heterotrophic eukaryotes with tissues that develop from embryonic layers There are exceptions to nearly every criterion for distinguishing animals from other life forms Several characteristics, taken together, sufficiently define the group

4 Nutritional Mode Animals are heterotrophs that ingest their food

5 Cell Structure and SpecializationAnimals are multicellular eukaryotes Their cells lack cell walls

6 Their bodies are held together by structural proteins such as collagenNervous tissue and muscle tissue are unique to animals

7 Reproduction and DevelopmentMost animals reproduce sexually, with the diploid stage usually dominating the life cycle

8 Video: Sea Urchin Embryonic DevelopmentAfter a sperm fertilizes an egg, the zygote undergoes cleavage, leading to formation of a blastula The blastula undergoes gastrulation, forming embryonic tissue layers and a gastrula Video: Sea Urchin Embryonic Development

9 LE 32-2_3 Blastocoel Cleavage Cleavage Zygote Eight-cell stageBlastula Cross section of blastula Blastocoel Endoderm Ectoderm Gastrula Gastrulation Blastopore

10 Many animals have at least one larval stageA larva is sexually immature and morphologically distinct from the adult; it eventually undergoes metamorphosis

11 Concept 32.2: The history of animals may span more than a billion yearsThe animal kingdom includes not only great diversity of living species but also the even greater diversity of extinct ones The common ancestor of living animals may have lived 1.2 billion–800 million years ago This ancestor may have resembled modern choanoflagellates, protists that are the closest living relatives of animals

12 Concept 32.3: Animals can be characterized by “body plans”Zoologists sometimes categorize animals according to morphology and development A grade is a group of animal species with the same level of organizational complexity A body plan is the set of traits defining a grade

13 Symmetry Animals can be categorized according to the symmetry of their bodies, or lack of it

14 Some animals have radial symmetry, the form found in a flower pot

15 LE 32-7a Radial symmetry

16 The two-sided symmetry seen in a shovel is an example of bilateral symmetry

17 LE 32-7b Bilateral symmetry

18 Bilaterally symmetrical animals have:A dorsal (top) side and a ventral (bottom) side A right and left side Anterior (head) and posterior (tail) ends Cephalization, the development of a head

19 Tissues Animal body plans also vary according to the organization of the animal’s tissues Tissues are collections of specialized cells isolated from other tissues by membranous layers

20 Animal embryos have concentric layers called germ layers that form tissues and organsEctoderm is the germ layer covering the embryo’s surface Endoderm is the innermost germ layer Diploblastic animals have ectoderm and endoderm Triploblastic animals also have an intervening mesoderm layer

21 Body Cavities In triploblastic animals, a body cavity may be present or absent A true body cavity is called a coelom and is derived from mesoderm

22 Coelom Body covering (from ectoderm) Tissue layer lining coelomLE 32-8a Coelom Body covering (from ectoderm) Tissue layer lining coelom and suspending internal organs (from mesoderm) Digestive tract (from endoderm) Coelomate

23 A pseudocoelom is a body cavity derived from the blastocoel, rather than from mesoderm

24 Body covering (from ectoderm) Pseudocoelom Muscle layer (fromLE 32-8b Body covering (from ectoderm) Pseudocoelom Muscle layer (from mesoderm) Digestive tract (from endoderm) Pseudocoelomate

25 Acoelomates are organisms without body cavities

26 Wall of digestive cavity (from endoderm)LE 32-8c Body covering (from ectoderm) Tissue- filled region (from mesoderm) Wall of digestive cavity (from endoderm) Acoelomate

27 Protostome and Deuterostome DevelopmentBased on early development, many animals can be categorized as having protostome or deuterostome development

28 Cleavage In protostome development, cleavage is spiral and determinateIn deuterostome development, cleavage is radial and indeterminate

29 Protostome development (examples: molluscs, annnelids, arthropods) LE 32-9a Protostome development (examples: molluscs, annnelids, arthropods) Deuterostome development (examples: echinoderms, chordates) Cleavage Eight-cell stage Eight-cell stage Spiral and determinate Radial and indeterminate

30 Coelom Formation In protostome development, the splitting of solid masses of mesoderm to form the coelomic cavity is called schizocoelous development In deuterostome development, formation of the body cavity is described as enterocoelous development

31 Protostome development (examples: molluscs, annnelids, arthropods) LE 32-9b Protostome development (examples: molluscs, annnelids, arthropods) Deuterostome development (examples: echinoderms, chordates) Coelom formation Coelom Archenteron Coelom Mesoderm Blastopore Blastopore Mesoderm Schizocoelous: solid masses of mesoderm split and form coelom Enterocoelous: folds of archenteron form coelom

32 Fate of the Blastopore In protostome development, the blastopore becomes the mouth In deuterostome development, the blastopore becomes the anus

33 Protostome development (examples: molluscs, annnelids, arthropods) LE 32-9c Protostome development (examples: molluscs, annnelids, arthropods) Deuterostome development (examples: echinoderms, chordates) Fate of the blastopore Anus Mouth Digestive tube Mouth Anus Mouth develops from blastopore Anus develops from blastopore