Chapter 32: Introduction to Animal EvolutionChapter 33: Invertebrates

Overview of Animal Phylogeny

part 1: invertebrates

Invertebrates: orientation to topics

Figure 33.1 Review of animal phylogeny

Table 25-1a

The Situation in the Late Precambrian

Precambrian origin of integrated organisms and basic body plans

Parazoa (Porifera) spongesRadiata (Cnidaria) sea anemones

and sea pensBilateralia

Protostomesprimitive

molluscs unidentified

worms

Charnia masoni - a sea pen Dickinsonia costata - annelid?

Fossils from the End of the Precambrian…

Figure 32.8 Animal phylogeny based on sequencing of SSU-rRNA

colonial choanoflagellate

Figure 33.2 Sponges

Figure 33.3 Anatomy of a sponge

Sponges have specialized cells,But they lack true tissues, groups of similar cells that act as a functional unit and are Isolated from other tissues byMembranous layers.

Figure 32.8 Animal phylogeny based on sequencing of SSU-rRNA

Figure 33.6 Cnidarians: Hydrozoans (top left), jelly (top right), sea anemone (bottom left), coral polyps (bottom right)

Figure 33.5 A cnidocyte of a hydra

Figure 33.4bx Jelly medusa

Figure 33.4 Polyp and medusa forms of cnidarians

A cnidarian life cycle

Figure 26.8 The Cambrian radiation of animals

(Ediacaran)

525BurgessShale

PLPL PL

PE

DD

RP

Figure 32.13x Burgess Shale fossils

Figure 32.13 A sample of some of the animals that evolved during the Cambrian explosion

Porifera and Cnidaria are prominent in the Burgess Shale

Annelid worms in the Burgess shale

Anomalocaris hunts

so are arthropods!!

Fossils of recognizable phyla in the Burgess shale

Mystery animals in the Burgess shale

Wiwaxia corrugata

Dinomischus

Figure 26.8 The Cambrian radiation of animals

Causes of the radiation:

1. Predator-prey relationships originate.

2. Atmospheric oxygen reaches sufficient levels.

3. Homeobox genes evolve.

(Ediacaran)

525BurgessShale

PLPL PL

PE

DD

RP

Figure 32.8 Animal phylogeny based on sequencing of SSU-rRNA

Figure 33.1 Review of animal phylogeny

Figure 32.8 Animal phylogeny based on sequencing of SSU-rRNA

trochophore

lophophore

Prominent Phyla of Lophotrochozoans

Figure 33.14 Lophophorates: Bryozoan (left), brachiopod (right)

LOPHOPHORE

The fate of the brachiopods

BrachiopodsBivalves

millions of years ago

Figure 32.8 Animal phylogeny based on sequencing of SSU-rRNA

trochophore

lophophore

Figure 32.6 Body plans of the bilateria

Figure 33.22 Cephalopods: Squid (top left and bottom left), nautilus (top right), octopus (bottom right)

Figure 33.17 A chiton

Figure 33.21 Anatomy of a clam

Molluscs are coelomate, lophotrochozoan protostomes with a foot and a mantle

Ammonites - extinct since the Cretaceous, along with dinosaurs

Lophotrochozoans, a clade identified by molecular data, have the widest range of body forms.

Figure 32.8 Animal phylogeny based on sequencing of SSU-rRNA

lophophore

Nematodes – ecdysozoans with priminent medical significance

hookworms

Trichinella – the nematode that causes trichinosis

CRUSTACEANS as examples of ARTHROPODA

Figure 33.28 Horseshoe crabs, Limulus polyphemus

Figure 33.27 A trilobite fossil

Figure 33.x1 Insecta: beetle

Figure 32.8 Animal phylogeny based on sequencing of SSU-rRNA

Figure 32.7 A comparison of early development in protostomes and deuterostomes

Figure 33.37 Echinoderms: Sea star (top left), brittle star (top right), sea urchin (bottom left), sea lily (bottom right),

fossil crinoids