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32An Overview of Animal DiversityLecture Presentation by Nicole Tunbridge andKathleen FitzpatrickCAMPBELLBIOLOGYReece Urry Cain Wasserman Minorsky Jackson 2014 Pearson Education, Inc.TENTHEDITION 2014 Pearson Education, Inc.A Kingdom of ConsumersMost animals are mobile and use traits such as strength, speed, toxins, or camouflage to detect, capture, and eat other organisms For example, the chameleon captures insect prey with its long, sticky, quick-moving tongue 2014 Pearson Education, Inc.2

Figure 32.1 2014 Pearson Education, Inc.Figure 32.1 What adaptations make a chameleon a fearsome predator?3

Figure 32.1a 2014 Pearson Education, Inc.Figure 32.1a What adaptations make a chameleon a fearsome predator? (part 1: close-up)4Concept 32.1: Animals are multicellular, heterotrophic eukaryotes with tissues that develop from embryonic layersThere are exceptions to nearly every criterion for distinguishing animals from other life-formsSeveral characteristics, taken together, sufficiently define the group 2014 Pearson Education, Inc.5Nutritional ModeAnimals are heterotrophs that ingest their food 2014 Pearson Education, Inc.6Cell Structure and SpecializationAnimals are multicellular eukaryotesTheir cells lack cell wallsTheir bodies are held together by structural proteins such as collagenNervous tissue and muscle tissue are unique, defining characteristics of animalsTissues are groups of similar cells that act as a functional unit

2014 Pearson Education, Inc.7Reproduction and DevelopmentMost animals reproduce sexually, with the diploid stage usually dominating the life cycleAfter a sperm fertilizes an egg, the zygote undergoes rapid cell division called cleavageCleavage leads to formation of a multicellular, hollow blastulaThe blastula undergoes gastrulation, forming a gastrula with different layers of embryonic tissues 2014 Pearson Education, Inc.8

Figure 32.2-3ZygoteCleavageEight-cellstageCleavageBlastocoelCross sectionof blastulaBlastulaGastrulationBlastocoelEndodermEctodermArchenteronCross sectionof gastrulaBlastopore 2014 Pearson Education, Inc.Figure 32.2-3 Early embryonic development in animals (step 3)9Video: Sea Urchin Embryonic Development (Time Lapse)

2014 Pearson Education, Inc.Most animals have at least one larval stageA larva is sexually immature and morphologically distinct from the adult; it eventually undergoes metamorphosis to become a juvenileA juvenile resembles an adult, but is not yet sexually mature 2014 Pearson Education, Inc.11Most animals, and only animals, have Hox genes that regulate the development of body formAlthough the Hox family of genes has been highly conserved, it can produce a wide diversity of animal morphology 2014 Pearson Education, Inc.12Concept 32.2: The history of animals spans more than half a billion yearsMore than 1.3 million animal species have been named to date; far more are estimated to existThe common ancestor of all living animals likely lived between 700 and 770 million years ago

2014 Pearson Education, Inc.13Steps in the Origin of Multicellular AnimalsMorphological and molecular evidence points to a group of protists called choanoflagellates as the closest living relatives to animalsThe common ancestor may have resembled modern choanoflagellates 2014 Pearson Education, Inc.14

Figure 32.3IndividualchoanoflagellateChoano-flagellatesOTHEREUKARYOTESSpongesOtheranimalsCollar cell(choanocyte)Animals 2014 Pearson Education, Inc.Figure 32.3 Three lines of evidence that choanoflagellates are closely related to animals15The origin of multicellularity requires the evolution of new ways for cells to adhere (attach) and signal (communicate) to each otherMolecular analysis has revealed similarities between genes coding for proteins involved in adherence and attachment in choanoflagellates and animals 2014 Pearson Education, Inc.16

Figure 32.4Choano-flagellateHydraFruitflyMouseCCD domain (onlyfound in animals) 2014 Pearson Education, Inc.Figure 32.4 Cadherin proteins in choanoflagellates and animals17Neoproterozoic Era (1 Billion542 Million Years Ago)Early members of the animal fossil record include the Ediacaran biota, which dates back to about 560 million years agoEarly animal embryos and evidence of predation have also been found in Neoproterozoic rocks

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Figure 32.51.5 cm(a)Mawsonites spriggi0.4 cm(b)Spriggina floundersi 2014 Pearson Education, Inc.Figure 32.5 Ediacaran fossil animals19

Figure 32.6Bore hole0.1 mm 2014 Pearson Education, Inc.Figure 32.6 Early evidence of predation20Paleozoic Era (542251 Million Years Ago)The Cambrian explosion (535 to 525 million years ago) marks the earliest fossil appearance of many major groups of living animalsMost of the fossils from the Cambrian explosion are of bilaterians, organisms that have the following traits:Bilaterally symmetric formComplete digestive tractOne-way digestive system 2014 Pearson Education, Inc.21

Figure 32.7Hallucigenia fossil (530 mya)1 cm 2014 Pearson Education, Inc.Figure 32.7 A Cambrian seascape22There are several hypotheses regarding the cause of the Cambrian explosion and decline of Ediacaran biotaNew predator-prey relationshipsA rise in atmospheric oxygenThe evolution of the Hox gene complex 2014 Pearson Education, Inc.23Animal diversity continued to increase through the Paleozoic, but was punctuated by mass extinctionsAnimals began to make an impact on land by 450 million years agoVertebrates made the transition to land around 365 million years ago 2014 Pearson Education, Inc.24Mesozoic Era (25165.5 Million Years Ago)Coral reefs emerged, becoming important marine ecological niches for other organismsThe ancestors of plesiosaurs were reptiles that returned to the waterDuring the Mesozoic era, dinosaurs were the dominant terrestrial vertebratesThe first mammals emergedFlowering plants and insects diversified 2014 Pearson Education, Inc.25Cenozoic Era (65.5 Million Years Ago to the Present)The beginning of the Cenozoic era followed mass extinctions of both terrestrial and marine animalsThese extinctions included the large, nonflying dinosaurs and the marine reptilesMammals increased in size and exploited vacated ecological nichesThe global climate cooled 2014 Pearson Education, Inc.26Concept 32.3: Animals can be characterized by body plansZoologists sometimes categorize animals according to a body plan, a set of morphological and developmental traitsSome body plans have been conserved, while others have changed multiple times over the course of evolution 2014 Pearson Education, Inc.27SymmetryAnimals can be categorized according to the symmetry of their bodies, or lack of itSome animals have radial symmetry, with no front and back, or left and right 2014 Pearson Education, Inc.28

Figure 32.8(a)Radial symmetryBilateral symmetry(b) 2014 Pearson Education, Inc.Figure 32.8 Body symmetry29Two-sided symmetry is called bilateral symmetryBilaterally symmetrical animals haveA dorsal (top) side and a ventral (bottom) sideA right and left sideAnterior (front) and posterior (back) endsMany also have sensory equipment, such as a brain, concentrated in their anterior end

2014 Pearson Education, Inc.30Radial animals are often sessile or planktonic (drifting or weakly swimming)Bilateral animals often move actively and have a central nervous system

2014 Pearson Education, Inc.31TissuesAnimal body plans also vary according to the organization of the animals tissuesTissues are collections of specialized cells isolated from other tissues by membranous layersDuring development, three germ layers give rise to the tissues and organs of the animal embryo

2014 Pearson Education, Inc.32Ectoderm is the germ layer covering the embryos surfaceEndoderm is the innermost germ layer and lines the developing digestive tube, called the archenteron 2014 Pearson Education, Inc.33Sponges and a few other groups lack true tissuesDiploblastic animals have ectoderm and endodermThese include cnidarians and a few other groupsTriploblastic animals also have an intervening mesoderm layer; these include all bilateriansThese include flatworms, arthropods, vertebrates, and others 2014 Pearson Education, Inc.34Body CavitiesMost triploblastic animals possess a body cavityA true body cavity is called a coelom and is derived from mesodermCoelomates are animals that possess a true coelom 2014 Pearson Education, Inc.35

Figure 32.9(a)CoelomateKeyEctodermMesodermEndodermCoelomBody covering(from ectoderm)Tissue layerlining coelomand suspendinginternal organs(from mesoderm)Digestive tract(from endoderm)Body covering(from ectoderm)Muscle layer(frommesoderm)Pseudo-coelomDigestive tract(from endoderm)(c)AcoelomateBody covering(from ectoderm)Tissue-filled region(frommesoderm)Wall of digestive cavity(from endoderm)(b)Psuedocoelomate 2014 Pearson Education, Inc.Figure 32.9 Body cavities of triploblastic animals36A pseudocoelom is a body cavity derived from the mesoderm and endodermTriploblastic animals that possess a pseudocoelom are called pseudocoelomates 2014 Pearson Education, Inc.37Triploblastic animals that lack a body cavity are called acoelomates 2014 Pearson Education, Inc.38Terms such as coelomates and pseudocoelomates refer to organisms that have a similar body plan and belong to the same gradeA grade is a group whose members share key biological featuresA grade is not necessarily a clade, an ancestor and all of its descendants 2014 Pearson Education, Inc.39Protostome and Deuterostome DevelopmentBased on early development, many animals can be categorized as having protostome development or deuterostome development 2014 Pearson Education, Inc.40CleavageIn protostome development, cleavage is spiral and determinateIn deuterostome development, cleavage is radial and indeterminateWith indeterminate cleavage, each cell in the early stages of cleavage retains the capacity to develop into a complete embryoIndeterminate cleavage makes possible identical twins, and embryonic stem cells 2014 Pearson Education, Inc.41

Figure 32.10Protostome development(examples: molluscs,annelids)Deuterostome development(examples: echinoderms,chordates)(a)CleavageKeyEctodermMesodermEndoderm(b)Coelomformation(c)Fate of theblastoporeEight-cell stageEight-cell stageSpiral and determinateRadial and indeterminateCoelomArchenteronCoelomMesodermBlastoporeSolid masses of mesodermsplit and form coelom.Folds of archenteronform coelom.BlastoporeMesodermAnusDigestive tubeMouthAnusMouthMouth develops from blastopore.Anus develops from blastopore. 2014 Pearson Education, Inc.Figure 32.10 A comparison of protostome and deuterostome development42Coelom FormationIn protostome development, the splitting of solid masses of mesoderm forms the coelomIn deuterostome development, the mesoderm buds from the wall of the archenteron to form the coelom 2014 Pearson Education, Inc.43Fate of the BlastoporeThe blastopore forms during gastrulation and connects the archenteron to the exterior of the gastrulaIn protostome development, the blastopore becomes the mouthIn deuterostome development, the blastopore becomes the anus 2014 Pearson Education, Inc.44Concept 32.4: Views of animal phylogeny continue to be shaped by new molecular and morphological dataBy 500 million years ago, most animal phyla with members alive today were established 2014 Pearson Education, Inc.45The Diversification of AnimalsZoologists recognize about three dozen animal phylaPhylogenies now combine morphological, molecular, and fossil data 2014 Pearson Education, Inc.46Five important points about the relationships among living animals are reflected in their phylogeny1. All animals share a common ancestor2.Sponges are basal animals3.Eumetazoa (true animals) is a clade of animals with true tissues4.Most animal phyla belong to the clade Bilateria5.There are three major clades of bilaterian animals, all ofwhich are invertebrates, animals that lack a backbone, except Chordata, which are classified as vertebrates because they have a backbone 2014 Pearson Education, Inc.47

Figure 32.11ANCESTRALPROTISTPoriferaCtenophoraCnidariaAcoela770 millionyears ago680 millionyears ago670 millionyears agoMetazoaEumetazoaBilateriaHemichordataEchinodermataChordataPlatyhelminthesRotiferaEctoproctaBrachiopodaMolluscaAnnelidaNematodaArthropodaDeuterostomiaLophotrochozoaEcdysozoa 2014 Pearson Education, Inc.Figure 32.11 A phylogeny of living animals48The bilaterians are divided into three clades: Deuterostomia, Ecdysozoa, and LophotrochozoaDeuterostomia includes hemichordates (acorn worms), echinoderms (sea stars and relatives), and chordatesThis clade includes both vertebrates and invertebrates 2014 Pearson Education, Inc.49Ecdysozoa is a clade of invertebrates that shed their exoskeletons through a process called ecdysis

2014 Pearson Education, Inc.50Lophotrochozoa is another clade of bilaterian invertebratesSome lophotrochozoans have a feeding structure called a lophophoreOthers go through a distinct developmental stage called the trochophore larva 2014 Pearson Education, Inc.51

Figure 32.12Lophophore feedingstructures of an ectoproct(a)LophophoreStructure of a trochophorelarva(b)AnusMouthApical tuftof cilia 2014 Pearson Education, Inc.Figure 32.12 Morphological characteristics of lophotrochozoans52Future Directions in Animal SystematicsSystematics, like all fields of scientific research, is an ongoing, dynamic process of inquiryThree outstanding questions are the focus of current research1.Are sponges monophyletic?2.Are ctenophores basal metazoans?3.Are acoelomate flatworms basal bilaterians? 2014 Pearson Education, Inc.53

Figure 32.UN03Porifera(basal animals)CtenophoraCnidariaAcoela (basalbilaterians)DeuterostomiaLophotrochozoaEcdysozoaTruetissuesBilateralsymmetryThree germlayersMetazoaEumetazoaBilateria (most animals) 2014 Pearson Education, Inc.Figure 32.UN03 Summary of key concepts: key steps in animal evolution 54