An Introduction to Animal Diversity

What Is an Animal?An Overview of Animal Phylogeny and DiversityThe Origins of Animal Diversity

What Is an Animal?

Multicellular, eukaryotic, heterotrophic, ingestion feeder, stores glycogen, nervous system, no cell walls, muscle system, sexual, flagellated sperm, dominant diploid

Zygotecleavageblastulagastrula larva with metamorphosis

Figure 32.1 Early embryonic development (Layer 1)

Overview of Animal Diversity and Phylogeny

Diversified during Precambrian and Cambrian periods

Monophyletic Parazoans-first branch, lack true tissues Radiata and bilateria two major branches of

Eumetazoa Evolution of body cavities Protostomes and deuterostomes

Parazoa

Sponges “beside the animals” Simple aquatic and marine forms

Eumetazoa

Two major branches: 1. Radiata-radial symmetry, top and

bottom, no front, back, or sides,

diploblastic larva 2. Bilateria-bilateral symmetry,

triploblastic,

cephalization

Importance of Coelom

Acoelomates-no body cavity, Platyhelminthes Pseudocoelomates-fluid filled body cavity,

partially lined with mesoderm, Nematoda Coelomates-fluid filled, completely lined with

mesoderm, Annelida Coelom-body cavity that protects internal organs

Protostomes and Deuterostomes

Protostomes: Mollusks, Annelids,

Arthropods Spiral cleavage Determinate cleavage Blastopore forms the

mouth schizocoelous

Deuterostomes: Echinoderms and

Chordates Radial cleavage Indeterminate

cleavage Blastopore forms the

anus Enterocoelous

The Origins of Animal Diversity

Colonial protist origin during Cambrian Explosion Evidence from fossil beds: Burgess Shale,

Yunnan region, Greenland Why such rapid diversification?

1. Adaptive radiation

2. Predator-prey relationships

3. Higher concentration of oxygen

Videos and Websites

• http://animaldiversity.ummz.umich.edu/site/index.html