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Figure 32.1 CAMPBELL BIOLOGY Figure 32.1a A Kingdom of Consumers TENTH EDITION Reece • Urry • Cain • Wasserman • Minorsky • Jackson ! Most animals are mobile and use traits such as strength, speed, toxins, or camouflage to detect, capture, and eat other organisms 32 ! For example, the chameleon captures insect prey with its long, sticky, quick-moving tongue An Overview of Animal Diversity Lecture Presentation by Nicole Tunbridge and Kathleen Fitzpatrick 2 3 4 © 2014 Pearson Education, Inc. © 2014 Pearson Education, Inc. © 2014 Pearson Education, Inc. © 2014 Pearson Education, Inc. Concept 32.1: Animals are multicellular, heterotrophic eukaryotes with tissues that develop from embryonic layers Nutritional Mode Cell Structure and Specialization Reproduction and Development ! Animals are heterotrophs that ingest their food ! Animals are multicellular eukaryotes ! There are exceptions to nearly every criterion for distinguishing animals from other life-forms ! Their cells lack cell walls ! Several characteristics, taken together, sufficiently define the group ! Their bodies are held together by structural proteins such as collagen ! Most animals reproduce sexually, with the diploid stage usually dominating the life cycle ! After a sperm fertilizes an egg, the zygote undergoes rapid cell division called cleavage ! Cleavage leads to formation of a multicellular, hollow blastula ! Nervous tissue and muscle tissue are unique, defining characteristics of animals ! The blastula undergoes gastrulation, forming a gastrula with different layers of embryonic tissues ! Tissues are groups of similar cells that act as a functional unit 5 © 2014 Pearson Education, Inc. 6 © 2014 Pearson Education, Inc. Figure 32.2-1 Figure 32.2-2 Zygote 7 © 2014 Pearson Education, Inc. Figure 32.2-3 Zygote Cleavage Zygote Cleavage Eight-cell stage 8 © 2014 Pearson Education, Inc. Eight-cell stage Eight-cell stage Cleavage Blastula Video: Sea Urchin Embryonic Development (Time Lapse) Cleavage Blastocoel Cleavage Cross section of blastula Blastula Blastocoel Cross section of blastula Gastrulation Cross section of gastrula 9 © 2014 Pearson Education, Inc. 10 © 2014 Pearson Education, Inc. Blastopore © 2014 Pearson Education, Inc. Blastocoel Endoderm Ectoderm Archenteron 11 Concept 32.2: The history of animals spans more than half a billion years ! Most animals have at least one larval stage ! A larva is sexually immature and morphologically distinct from the adult; it eventually undergoes metamorphosis to become a juvenile ! A juvenile resembles an adult, but is not yet sexually mature ! Most animals, and only animals, have Hox genes that regulate the development of body form ! More than 1.3 million animal species have been named to date; far more are estimated to exist ! Although the Hox family of genes has been highly conserved, it can produce a wide diversity of animal morphology ! The common ancestor of all living animals likely lived between 700 and 770 million years ago 13 © 2014 Pearson Education, Inc. 14 © 2014 Pearson Education, Inc. 12 © 2014 Pearson Education, Inc. Steps in the Origin of Multicellular Animals ! Morphological and molecular evidence points to a group of protists called choanoflagellates as the closest living relatives to animals ! The common ancestor may have resembled modern choanoflagellates 15 © 2014 Pearson Education, Inc. 16 © 2014 Pearson Education, Inc. Figure 32.3 Figure 32.4 Neoproterozoic Era (1 Billion–542 Million Years Ago) ! The origin of multicellularity requires the evolution of new ways for cells to adhere (attach) and signal (communicate) to each other Individual choanoflagellate Choanoflagellates OTHER EUKARYOTES ! Molecular analysis has revealed similarities between genes coding for proteins involved in adherence and attachment in choanoflagellates and animals Sponges Animals 17 © 2014 Pearson Education, Inc. “CCD” domain (only found in animals) Fruit fly Mouse 18 © 2014 Pearson Education, Inc. Figure 32.5 19 © 2014 Pearson Education, Inc. Figure 32.5a 1.5 cm ! Early animal embryos and evidence of predation have also been found in Neoproterozoic rocks Hydra Collar cell (choanocyte) Other animals ! Early members of the animal fossil record include the Ediacaran biota, which dates back to about 560 million years ago Choanoflagellate Figure 32.5b 1.5 cm 0.4 cm 20 © 2014 Pearson Education, Inc. Figure 32.6 0.4 cm Bore hole 0.1 mm (a) Mawsonites spriggi (b) Spriggina floundersi (a) Mawsonites spriggi 21 © 2014 Pearson Education, Inc. (b) Spriggina floundersi 22 © 2014 Pearson Education, Inc. 23 © 2014 Pearson Education, Inc. Figure 32.7 24 © 2014 Pearson Education, Inc. Figure 32.7a Figure 32.7b Paleozoic Era (542–251 Million Years Ago) ! The Cambrian explosion (535 to 525 million years ago) marks the earliest fossil appearance of many major groups of living animals ! Most of the fossils from the Cambrian explosion are of bilaterians, organisms that have the following traits: 1 cm Hallucigenia fossil (530 mya) ! Bilaterally symmetric form 1 cm ! Complete digestive tract Hallucigenia fossil (530 mya) ! One-way digestive system 25 © 2014 Pearson Education, Inc. 26 © 2014 Pearson Education, Inc. ! There are several hypotheses regarding the cause of the Cambrian explosion and decline of Ediacaran biota ! New predator-prey relationships ! Animal diversity continued to increase through the Paleozoic, but was punctuated by mass extinctions ! Animals began to make an impact on land by 450 million years ago ! A rise in atmospheric oxygen ! Vertebrates made the transition to land around 365 million years ago ! The evolution of the Hox gene complex 27 28 © 2014 Pearson Education, Inc. © 2014 Pearson Education, Inc. Mesozoic Era (251–65.5 Million Years Ago) Cenozoic Era (65.5 Million Years Ago to the Present) ! Coral reefs emerged, becoming important marine ecological niches for other organisms ! The beginning of the Cenozoic era followed mass extinctions of both terrestrial and marine animals ! The ancestors of plesiosaurs were reptiles that returned to the water ! These extinctions included the large, nonflying dinosaurs and the marine reptiles ! During the Mesozoic era, dinosaurs were the dominant terrestrial vertebrates ! Mammals increased in size and exploited vacated ecological niches ! The first mammals emerged ! The global climate cooled ! Flowering plants and insects diversified 29 © 2014 Pearson Education, Inc. 30 © 2014 Pearson Education, Inc. 31 © 2014 Pearson Education, Inc. 32 © 2014 Pearson Education, Inc. Figure 32.8 Concept 32.3: Animals can be characterized by “body plans” ! Zoologists sometimes categorize animals according to a body plan, a set of morphological and developmental traits Symmetry ! Animals can be categorized according to the symmetry of their bodies, or lack of it ! Two-sided symmetry is called bilateral symmetry ! Bilaterally symmetrical animals have ! Some animals have radial symmetry, with no front and back, or left and right ! Some body plans have been conserved, while others have changed multiple times over the course of evolution ! A dorsal (top) side and a ventral (bottom) side (a) Radial symmetry ! A right and left side ! Anterior (front) and posterior (back) ends ! Many also have sensory equipment, such as a brain, concentrated in their anterior end (b) Bilateral symmetry 33 © 2014 Pearson Education, Inc. 34 © 2014 Pearson Education, Inc. 35 © 2014 Pearson Education, Inc. 36 © 2014 Pearson Education, Inc. Tissues ! Radial animals are often sessile or planktonic (drifting or weakly swimming) ! Animal body plans also vary according to the organization of the animal’s tissues ! Ectoderm is the germ layer covering the embryo’s surface ! Bilateral animals often move actively and have a central nervous system ! Tissues are collections of specialized cells isolated from other tissues by membranous layers ! Endoderm is the innermost germ layer and lines the developing digestive tube, called the archenteron ! During development, three germ layers give rise to the tissues and organs of the animal embryo ! Sponges and a few other groups lack true tissues ! Diploblastic animals have ectoderm and endoderm ! These include cnidarians and a few other groups ! Triploblastic animals also have an intervening mesoderm layer; these include all bilaterians ! These include flatworms, arthropods, vertebrates, and others 37 © 2014 Pearson Education, Inc. 38 © 2014 Pearson Education, Inc. 39 © 2014 Pearson Education, Inc. Figure 32.9 40 © 2014 Pearson Education, Inc. Figure 32.9a Figure 32.9b Body Cavities (b) Psuedocoelomate (a) Coelomate ! Most triploblastic animals possess a body cavity Coelom ! A true body cavity is called a coelom and is derived from mesoderm Digestive tract (from endoderm) ! Coelomates are animals that possess a true coelom Body covering (from ectoderm) Body covering (from ectoderm) Tissue layer lining coelom and suspending internal organs (from mesoderm) Pseudocoelom (a) Coelomate (b) Pseudocoelomate Coelom Muscle layer (from mesoderm) Digestive tract (from endoderm) (c) Acoelomate Key Ectoderm Body covering (from ectoderm) Wall of digestive cavity (from endoderm) Tissuefilled region (from mesoderm) Pseudocoelom Tissue layer lining coelom and suspending internal organs (from mesoderm) Ectoderm Mesoderm Digestive tract (from endoderm) Ectoderm Endoderm 42 © 2014 Pearson Education, Inc. Muscle layer (from mesoderm) Key Key Endoderm 41 © 2014 Pearson Education, Inc. Digestive tract (from endoderm) Mesoderm Body covering (from ectoderm) Body covering (from ectoderm) Mesoderm Endoderm 43 © 2014 Pearson Education, Inc. 44 © 2014 Pearson Education, Inc. Figure 32.9c ! A pseudocoelom is a body cavity derived from the mesoderm and endoderm (c) Acoelomate Body covering (from ectoderm) Tissuefilled region (from mesoderm) ! Terms such as coelomates and pseudocoelomates refer to organisms that have a similar body plan and belong to the same grade ! Triploblastic animals that possess a pseudocoelom are called pseudocoelomates ! A grade is a group whose members share key biological features ! A grade is not necessarily a clade, an ancestor and all of its descendants Wall of digestive cavity (from endoderm) Key Ectoderm Mesoderm Endoderm 45 © 2014 Pearson Education, Inc. ! Triploblastic animals that lack a body cavity are called acoelomates 46 © 2014 Pearson Education, Inc. 47 © 2014 Pearson Education, Inc. 48 © 2014 Pearson Education, Inc. Figure 32.10 Protostome and Deuterostome Development Figure 32.10a Cleavage (a) Cleavage ! Based on early development, many animals can be categorized as having protostome development or deuterostome development Protostome development (examples: molluscs, annelids) Eight-cell stage Deuterostome development (examples: echinoderms, chordates) Eight-cell stage ! In protostome development, cleavage is spiral and determinate Radial and indeterminate Spiral and determinate ! In deuterostome development, cleavage is radial and indeterminate ! Indeterminate cleavage makes possible identical twins, and embryonic stem cells 49 50 Protostome development (examples: molluscs, annelids) Eight-cell stage Deuterostome development (examples: echinoderms, chordates) Eight-cell stage Spiral and determinate Radial and indeterminate Coelom Mesoderm Blastopore Blastopore Solid masses of mesoderm split and form coelom. (c) Fate of the blastopore Mesoderm Folds of archenteron form coelom. Mouth Anus Digestive tube Key © 2014 Pearson Education, Inc. Figure 32.10b (a) Cleavage Archenteron ! With indeterminate cleavage, each cell in the early stages of cleavage retains the capacity to develop into a complete embryo © 2014 Pearson Education, Inc. Coelom (b) Coelom formation Ectoderm Mesoderm Endoderm Mouth Mouth develops from blastopore. Anus 51 Anus develops from blastopore. 52 © 2014 Pearson Education, Inc. © 2014 Pearson Education, Inc. Coelom Formation Fate of the Blastopore Figure 32.10c Protostome development (examples: molluscs, annelids) (b) Coelom formation Deuterostome development (examples: echinoderms, chordates) Coelom (c) Fate of the blastopore Protostome development (examples: molluscs, annelids) Anus Archenteron Digestive tube Coelom Key Mesoderm Ectoderm Mesoderm Endoderm Blastopore Solid masses of mesoderm split and form coelom. Deuterostome development (examples: echinoderms, chordates) Mouth Blastopore Mesoderm Folds of archenteron form coelom. ! In protostome development, the splitting of solid masses of mesoderm forms the coelom ! In deuterostome development, the mesoderm buds from the wall of the archenteron to form the coelom Key Ectoderm Mesoderm Endoderm Mouth Mouth develops from blastopore. 54 © 2014 Pearson Education, Inc. Concept 32.4: Views of animal phylogeny continue to be shaped by new molecular and morphological data The Diversification of Animals ! In protostome development, the blastopore becomes the mouth ! In deuterostome development, the blastopore becomes the anus Anus Anus develops from blastopore. 53 © 2014 Pearson Education, Inc. ! The blastopore forms during gastrulation and connects the archenteron to the exterior of the gastrula 55 © 2014 Pearson Education, Inc. 56 © 2014 Pearson Education, Inc. Figure 32.11 Porifera Hemichordata Echinodermata Chordata Platyhelminthes Lophotrochozoa Rotifera Ectoprocta Brachiopoda Mollusca Annelida Ecdysozoa 59 © 2014 Pearson Education, Inc. Deuterostomia Figure 32.11a Bilateria 58 Acoela 670 million years ago 5. There are three 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 © 2014 Pearson Education, Inc. Eumetazoa 2. Sponges are basal animals 4. Most animal phyla belong to the clade Bilateria 57 Cnidaria 680 million years ago 3. Eumetazoa (“true animals”) is a clade of animals with true tissues © 2014 Pearson Education, Inc. Ctenophora 770 million years ago 1. All animals share a common ancestor ! Phylogenies now combine morphological, molecular, and fossil data Metazoa ! Five important points about the relationships among living animals are reflected in their phylogeny ! Zoologists recognize about three dozen animal phyla ! By 500 million years ago, most animal phyla with members alive today were established ANCESTRAL PROTIST Nematoda Arthropoda 60 © 2014 Pearson Education, Inc. Figure 32.11b Deuterostomia Porifera Metazoa Ctenophora Cnidaria Acoela Bilateria 680 million years ago ! Ecdysozoa is a clade of invertebrates that shed their exoskeletons through a process called ecdysis ! Deuterostomia includes hemichordates (acorn worms), echinoderms (sea stars and relatives), and chordates Rotifera Ectoprocta Brachiopoda ! This clade includes both vertebrates and invertebrates Mollusca Annelida Ecdysozoa 670 million years ago 61 © 2014 Pearson Education, Inc. ! The bilaterians are divided into three clades: Deuterostomia, Ecdysozoa, and Lophotrochozoa Chordata Platyhelminthes Lophotrochozoa 770 million years ago Eumetazoa ANCESTRAL PROTIST Hemichordata Echinodermata © 2014 Pearson Education, Inc. Nematoda Arthropoda 62 63 © 2014 Pearson Education, Inc. 64 © 2014 Pearson Education, Inc. Figure 32.12 Figure 32.12a Future Directions in Animal Systematics ! Lophotrochozoa is another clade of bilaterian invertebrates Lophophore ! Systematics, like all fields of scientific research, is an ongoing, dynamic process of inquiry Lophophore Apical tuft of cilia ! Some lophotrochozoans have a feeding structure called a lophophore ! Three outstanding questions are the focus of current research ! Others go through a distinct developmental stage called the trochophore larva 1. Are sponges monophyletic? Mouth 2. Are ctenophores basal metazoans? Anus (a) Lophophore feeding structures of an ectoproct (b) Structure of a trochophore larva 65 © 2014 Pearson Education, Inc. 66 © 2014 Pearson Education, Inc. Figure 32.UN01 3. Are acoelomate flatworms basal bilaterians? (a) Lophophore feeding structures of an ectoproct 67 © 2014 Pearson Education, Inc. Figure 32.UN02 Figure 32.UN03 Figure 32.UN04 1 2 3 4 5 6 7 8 9 10 11 5.8 35 2.5 26 38.6 33 59.1 25 50.8 58 147.5 25 30 34 38 45 68 73 77 83 94 172.5 560 mya: Ediacaran animals Era Neoproterozoic 1,000 Σ Σ Sx 535−525 mya: Cambrian explosion Σ 542 365 mya: Early land animals Origin and diversification of dinosaurs Paleozoic 251 Millions of years ago (mya) Ctenophora Diversification of mammals Mesozoic Cenozoic 65.5 Cnidaria True tissues Acoela (basal bilaterians) Deuterostomia 0 Bilateral symmetry Sy Three germ layers 69 © 2014 Pearson Education, Inc. Figure 32.UN05 73 © 2014 Pearson Education, Inc. 70 © 2014 Pearson Education, Inc. Lophotrochozoa Ecdysozoa Bilateria (most animals) i Eumetazoa Animal Phylum Porifera Platyhelminthes Cnidaria Nematoda Echinodermata Cephalochordata Arthropoda Urochordata Mollusca Annelida Vertebrata No. of Cell Types (yi) Metazoa Porifera (basal animals) No. of miRNAs (xi) 68 © 2014 Pearson Education, Inc. Blastopore Fate Phyla Protostomy (P) Platyhelminthes, Rotifera, Nematoda; most Mollusca, most Annelida; few Arthropoda Deuterostomy (D) Echinodermata, Chordata; most Arthropoda; few Mollusca, few Annelida Neither (N) Acoela Source: A. Hejnol and M. Martindale, The mouth, the anus, and the blastopore open questions about questionable openings. In Animal Evolution: Genomes, Fossils and Trees, eds. D. T. J. Littlewood and M. J. Telford, Oxford University Press, pp. 33–40 (2009). 71 © 2014 Pearson Education, Inc. 72 © 2014 Pearson Education, Inc.