An Overview of Animal Diversity Chapter 32 An Overview of Animal Diversity

Overview: Welcome to Your Kingdom Scientists have identified 1.3 million living species of animals How many more would you guess there are? © 2011 Pearson Education, Inc.

Video: Coral Reef © 2011 Pearson Education, Inc.

Which of these organisms are animals? Figure 32.1 Which of these organisms are animals? Figure 32.1 4

How do you define “animals”? © 2011 Pearson Education, Inc.

How do you define “animals”? Eukaryotic Multicellular Heterotrophic…via ingestion Have tissues, except for the basal taxon (sponges) Have nervous and muscle tissue…usually Motile…usually at least for a phase Cells do not have walls, but instead are held together by collagen (derived trait) Have blastula phase (usually) which undergoes gastrulation forming tissue layers (two or three) Most animals, and only animals, have Hox genes that regulate the development of body form © 2011 Pearson Education, Inc. 6

Video: Sea Urchin Embryonic Development © 2011 Pearson Education, Inc.

Early embryonic development in animals Figure 32.2-1 Early embryonic development in animals Zygote Cleavage Eight-cell stage Figure 32.2 Early embryonic development in animals. 8

Cross section of blastula Figure 32.2-2 Early embryonic development in animals Zygote Cleavage Blastocoel Cleavage Eight-cell stage Cross section of blastula Blastula Figure 32.2 Early embryonic development in animals. 9

Cross section of blastula Cross section of gastrula Figure 32.2-3 Early embryonic development in animals Zygote Cleavage Blastocoel Cleavage Eight-cell stage Cross section of blastula Gastrulation Blastula Figure 32.2 Early embryonic development in animals. Blastocoel Endoderm Ectoderm Archenteron Cross section of gastrula Blastopore 10

Many animals have at least one larval stage What are some examples? Do humans have a larval stage? A larva is sexually immature and morphologically distinct from the adult; it eventually undergoes metamorphosis © 2011 Pearson Education, Inc.

Concept 32.2: The history of animals spans more than half a billion years What % of animal species are extinct? © 2011 Pearson Education, Inc. 12

Concept 32.2: The history of animals spans more than half a billion years What % of animal species are extinct? 99% The common ancestor of living animals may have lived between 675 and 800 million years ago This ancestor may have resembled modern choanoflagellates, protists that are the closest living relatives of animals © 2011 Pearson Education, Inc.

Greatn Grandma Individual choanoflagellate Choanoflagellates Figure 32.3 Greatn Grandma Individual choanoflagellate Choanoflagellates OTHER EUKARYOTES Sponges Figure 32.3 Three lines of evidence that choanoflagellates are closely related to animals. Animals Collar cell (choanocyte) Other animals 14

Neoproterozoic Era (1 Billion–542 Million Years Ago) Early members of the animal fossil record include the Ediacaran biota, which dates from 565 to 550 million years ago © 2011 Pearson Education, Inc.

(a) Mawsonites spriggi (b) Spriggina floundersi Figure 32.4 1.5 cm 0.4 cm Figure 32.4 Ediacaran fossils. (a) Mawsonites spriggi (b) Spriggina floundersi 16

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 There are several hypotheses regarding the cause of the Cambrian explosion and decline of Ediacaran biota New predator-prey relationships A rise in atmospheric oxygen The evolution of the Hox gene complex © 2011 Pearson Education, Inc.

Figure 32.5 Figure 32.5 A Cambrian seascape. 18

Animals began to make an impact on land by 460 million years ago Animal diversity continued to increase through the Paleozoic, but was punctuated by mass extinctions Animals began to make an impact on land by 460 million years ago How can we tell this? Vertebrates made the transition to land around 360 million years ago © 2011 Pearson Education, Inc.

Mesozoic Era (251–65.5 Million Years Ago) Coral reefs emerged, becoming important marine ecological niches for other organisms The ancestors of plesiosaurs were reptiles that returned to the water During the Mesozoic era, dinosaurs were the dominant terrestrial vertebrates The first mammals emerged Flowering plants and insects diversified © 2011 Pearson Education, Inc.

Cenozoic Era (65.5 Million Years Ago to the Present) The beginning of the Cenozoic era followed mass extinctions of both terrestrial and marine animals These extinctions included the large, nonflying dinosaurs and the marine reptiles Mammals increased in size and exploited vacated ecological niches The global climate cooled © 2011 Pearson Education, Inc.

animals can have diverse body plans Radial symmetry: How would radial symmetry be advantageous? Figure 32.7 Body symmetry. (b) Bilateral symmetry: What behavior and morphological traits do bilateral animals have in common? 22

Two-sided symmetry is called bilateral symmetry 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 © 2011 Pearson Education, Inc.

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 Sponges and a few other groups lack true tissues During development, three germ layers give rise to the tissues and organs of the animal embryo © 2011 Pearson Education, Inc.

1. Ectoderm is the germ layer covering the embryo’s surface 2. Endoderm is the innermost germ layer and lines the developing digestive tube, called the archenteron Diploblastic animals have ectoderm and endoderm These include cnidarians and comb jellies Triploblastic animals also have an intervening mesoderm (#3) layer; these include all bilaterians These include flatworms, arthropods, vertebrates, and others © 2011 Pearson Education, Inc.

Body Cavities Most triploblastic animals possess a body cavity A true body cavity is called a coelom and is derived from mesoderm Coelomates are animals that possess a true coelom © 2011 Pearson Education, Inc.

Body covering (from ectoderm) Figure 32.8 (a) Coelomate Coelom Body covering (from ectoderm) Tissue layer lining coelom and suspending internal organs (from mesoderm) Digestive tract (from endoderm) (b) Pseudocoelomate Body covering (from ectoderm) Pseudocoelom Muscle layer (from mesoderm) Digestive tract (from endoderm) Figure 32.8 Body cavities of triploblastic animals. (c) Acoelomate Body covering (from ectoderm) Tissue- filled region (from mesoderm) Wall of digestive cavity (from endoderm) 27

Coelomates and pseudocoelomates belong to the same grade 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 © 2011 Pearson Education, Inc.

Protostome and Deuterostome Development Based on early development, many animals can be categorized as having protostome development or deuterostome development What are the roots of prototstome and deuterostome that give away their meanings? © 2011 Pearson Education, Inc.

Protostome development (examples: molluscs, annelids) Figure 32.9 Protostome development (examples: molluscs, annelids) Deuterostome development (examples: echinoderms, chordates) (a) Cleavage Eight-cell stage Eight-cell stage Spiral and determinate Radial and indeterminate (b) Coelom formation Coelom Archenteron Coelom Mesoderm Blastopore Blastopore Mesoderm Solid masses of mesoderm split and form coelom. Folds of archenteron form coelom. Figure 32.9 A comparison of protostome and deuterostome development. (c) Fate of the blastopore Anus Mouth Digestive tube Key Ectoderm Mouth Anus Mesoderm Mouth develops from blastopore. Anus develops from blastopore. Endoderm 30

Cleavage In protostome development, cleavage is spiral and determinate In deuterostome development, cleavage is radial and indeterminate With indeterminate cleavage, each cell in the early stages of cleavage retains the capacity to develop into a complete embryo Indeterminate cleavage makes possible identical twins, and embryonic stem cells © 2011 Pearson Education, Inc.

Animal phylogeny based on morphology Porifera Cnidaria ANCESTRAL COLONIAL FLAGELLATE Metazoa Ctenophora Eumetazoa Ectoprocta Brachiopoda Deuterostomia Echinodermata Chordata Bilateria Platyhelminthes Rotifera Figure 32.10 A view of animal phylogeny based mainly on morphological and developmental comparisons. Protostomia Mollusca Annelida Arthropoda Nematoda 32

Animal phylogeny based on molecular systematics Porifera ANCESTRAL COLONIAL FLAGELLATE Ctenophora Metazoa Cnidaria Eumetazoa Acoela Echinodermata Chordata Deuterostomia Bilateria Platyhelminthes Rotifera Ectoprocta Lophotrochozoa Figure 32.11 A view of animal phylogeny based mainly on molecular data. Brachiopoda Mollusca Annelida Nematoda Ecdysozoa Arthropoda 33

Points of Agreement All animals share a common ancestor Sponges are basal animals Eumetazoa is a clade of animals (eumetazoans) with true tissues Most animal phyla belong to the clade Bilateria, and are called bilaterians Chordates and some other phyla belong to the clade Deuterostomia © 2011 Pearson Education, Inc.

Progress in Resolving Bilaterian Relationships (we will cover in chapter 33) The morphology-based tree divides bilaterians into two clades: deuterostomes and protostomes In contrast, recent molecular studies indicate three bilaterian clades: Deuterostomia, Ecdysozoa, and Lophotrochozoa Ecdysozoans shed their exoskeletons through a process called ecdysis © 2011 Pearson Education, Inc.

Figure 32.12 Figure 32.12 Ecdysis. 36

Some lophotrochozoans have a feeding structure called a lophophore Others go through a distinct developmental stage called the trochophore larva © 2011 Pearson Education, Inc.

Lophophore feeding structures of an ectoproct (b) Figure 32.13 Apical tuft of cilia Lophophore Mouth Figure 32.13 Morphological characteristics of lophotrochozoans. Anus (a) Lophophore feeding structures of an ectoproct (b) Structure of a trochophore larva 38

Future Directions in Animal Systematics Phylogenetic studies based on larger databases will likely provide further insights into animal evolutionary history © 2011 Pearson Education, Inc.

535–525 mya: Cambrian explosion Figure 32.UN02 535–525 mya: Cambrian explosion Origin and diversification of dinosaurs 365 mya: Early land animals 565 mya: Ediacaran biota Diversification of mammals Era Ceno- zoic Neoproterozoic Paleozoic Mesozoic 1,000 542 Figure 32.UN02 Summary figure, Concept 32.2 251 65.5 Millions of years ago (mya) 40

Common ancestor of all animals Figure 32.UN03 Common ancestor of all animals Porifera (basal animals) Metazoa Ctenophora Eumetazoa Cnidaria True tissues Acoela (basal bilaterians) Figure 32.UN03 Summary figure, Concept 32.4 Deuterostomia Bilateria (most animals) Bilateral symmetry Lophotrochozoa Three germ layers Ecdysozoa 41

Homework: process ch 33 by completing the following table Phylum Key Characteristics Examples 1-2 pictures Porifera Cnidaria Ctenophores Platylhiminthes Rotifera Lophophorates Mollusca Annelida Nematoda Arthropoda Echinodermata Chordata