1. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Chapter 32 An Introduction to Animal Diversity “Abridged” version!

2. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Overview: Welcome to Your Kingdom Animal are multicellular Heterotrophic; must ingest their food Eukaryotes, with cells lacking cell walls Tissues that develop from embryonic layers – their bodies are held together by structural proteins such as collagen – Nervous tissue and muscle tissue are unique to animals

3. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The common ancestor of living animals – May have lived 1.2 billion–800 million years ago – May have resembled modern choanoflagellates, protists that are the closest living relatives of animals Single cell Stalk (a) (b)

4. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Several characteristics of animals sufficiently define their grouping and levels of complexity – Body plan Symmetry Tissues (types, layers) Body cavities (acoelomate, pseudocoelomate, eucoelomate) – Reproduction and development

5. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 32.3: Animals can be characterized by “body plans” One way in which zoologists categorize the diversity of animals – Is according to general features of morphology and development A group of animal species – That share the same level of organizational complexity is known as a grade

6. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 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

7. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Animal embryos – Form germ layers, embryonic tissues, including ectoderm, endoderm, and mesoderm Diploblastic animals – Have two germ layers Triploblastic animals – Have three germ layers

8. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Some animals have radial symmetry – Like in a flower pot Figure 32.7a Radial symmetry. The parts of a radial animal, such as a sea anemone (phylum Cnidaria), radiate from the center. Any imaginary slice through the central axis divides the animal into mirror images. (a)

9. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Some animals exhibit bilateral symmetry – Or two-sided symmetry Figure 32.7b Bilateral symmetry. A bilateral animal, such as a lobster (phylum Arthropoda), has a left side and a right side. Only one imaginary cut divides the animal into mirror-image halves. (b)

10. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Bilaterally symmetrical animals have – A dorsal (top) side and a ventral (bottom) side – A right and left side (lateral) – Anterior (head) and posterior (tail) ends – Cephalization, the development of a head with senses concentrated in one area, is considered an evolutionary step forward

11. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Body Cavities In triploblastic animals – A body cavity may be present or absent

12. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A true body cavity – Is called a coelom and is derived from mesoderm Figure 32.8a Coelom Body covering (from ectoderm) Digestive tract (from endoderm) Tissue layer lining coelom and suspending internal organs (from mesoderm) Coelomate. Coelomates such as annelids have a true coelom, a body cavity completely lined by tissue derived from mesoderm. (a)

13. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A pseudocoelom – Is a body cavity derived from the blastocoel, rather than from mesoderm Figure 32.8b Pseudocoelom Muscle layer (from mesoderm) Body covering (from ectoderm) Digestive tract (from ectoderm) Pseudocoelomate. Pseudocoelomates such as nematodes have a body cavity only partially lined by tissue derived from mesoderm. (b)

14. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Organisms without body cavities – Are considered acoelomates Figure 32.8c Body covering (from ectoderm) Tissue- filled region (from mesoderm) Digestive tract (from endoderm) Acoelomate. Acoelomates such as flatworms lack a body cavity between the digestive tract and outer body wall. (c)

15. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Reproduction and Development Most animals reproduce sexually – With the diploid stage usually dominating the life cycle After a sperm fertilizes an egg – The zygote undergoes cleavage, leading to the formation of a blastula The blastula undergoes gastrulation – Resulting in the formation of embryonic tissue layers and a gastrula

16. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Zygote Cleavage Eight-cell stage Cleavage Blastula Cross section of blastula Blastocoel Gastrula Gastrulation Endoderm Ectoderm Blastopore Early embryonic development in animals Figure 32.2 In most animals, cleavage results in the formation of a multicellular stage called a blastula. The blastula of many animals is a hollow ball of cells. 3 The endoderm of the archenteron de- velops into the tissue lining the animal’s digestive tract. 6 The blind pouch formed by gastru- lation, called the archenteron, opens to the outside via the blastopore. 5 Most animals also undergo gastrulation, a rearrangement of the embryo in which one end of the embryo folds inward, expands, and eventually fills the blastocoel, producing layers of embryonic tissues: the ectoderm (outer layer) and the endoderm (inner layer). 4 Only one cleavage stage–the eight-cell embryo–is shown here. 2 The zygote of an animal undergoes a succession of mitotic cell divisions called cleavage. 1

17. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Colonial protist, an aggregate of identical cells Hollow sphere of unspecialized cells (shown in cross section) Beginning of cell specialization Infolding Gastrula-like “protoanimal” Somatic cells Digestive cavity Reproductive cells

18. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Protostome and Deuterostome Development Based on certain features seen in early development – Many animals can be categorized as having one of two developmental modes: protostome development or deuterostome development

19. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cleavage In protostome development – Cleavage is spiral and determinate In deuterostome development – Cleavage is radial and indeterminate Figure 32.9a Protostome development (examples: molluscs, annelids, arthropods) Deuterostome development (examples: echinoderms, chordates) Eight-cell stage Spiral and determinate Radial and indeterminate (a) Cleavage. In general, protostome development begins with spiral, determinate cleavage. Deuterostome development is characterized by radial, indeterminate cleavage.

20. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Coelom Formation In protostome development – The splitting of the initially 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 Figure 32.9b Archenteron Blastopore Mesoderm Coelom Blastopore Mesoderm Schizocoelous: solid masses of mesoderm split and form coelom Enterocoelous: folds of archenteron form coelom Coelom (b) Coelom formation. Coelom formation begins in the gastrula stage. In protostome development, the coelom forms from splits in the mesoderm (schizocoelous development). In deuterostome development, the coelom forms from mesodermal outpocketings of the archenteron (enterocoelous development).

21. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fate of the Blastopore In protostome development – The blastopore becomes the mouth In deuterostome development – The blastopore becomes the anus Figure 32.9c Anus Mouth Mouth develops from blastopore Anus develops from blastopore Digestive tube

22. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 32.4: Leading hypotheses agree on major features of the animal phylogenetic tree Zoologists currently recognize about 35 animal phyla The current debate in animal systematics – Has led to the development of two phylogenetic hypotheses, but others exist as well

23. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings One hypothesis of animal phylogeny based mainly on molecular data Figure 32.11 Calcarea Silicarea Ctenophora Cnidaria Echinodermata Chordata Brachiopoda Phoronida Ectoprocta Platyhelminthes Nemertea Mollusca Annelida Rotifera Nematoda Arthropoda “Radiata” “Porifera” Deuterostomia Lophotrochozoa Ecdysozoa Bilateria Eumetazoa Metazoa Ancestral colonial flagellate

24. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings One hypothesis of animal phylogeny based mainly on morphological and developmental comparisons Figure 32.10 Porifera Cnidaria Ctenophora Phoronida Ectoprocta Brachiopoda Echinodermata Chordata Platyhelminthes Mollusca Annelida Arthropoda Rotifera Nemertea Nematoda “ Radiata ” Deuterostomia Protostomia Bilateria Eumetazoa Metazoa Ancestral colonial flagellate