Organizing Animal Phyla

Turn in the ocean acidification reading assignment, and locate your mollusk

notes outline

Mollusk quiz

• 15 minutes MAX!

TEST: TUESDAY 4.27

• TOPICS:– Annelids– Arthropods– Dichotomous keys– Mollusks– Echinodermata*– “Big 9” Phyla*

Simple Invertebrates• Some time ago, we studied the simple invertebrates:

• These animals all lack respiratory or circulatory organs, which is why we describe them as “simple.”

Porifora Cnidaria Platy-helminthes

Nematoda

Common Name

Sponges Jellyfish Flatworms Roundworms

Key Characteristic / Innovation

No tissues

Radial diploblasts

Triploblastic bilaterans

Through gut

Complex Invertebrates• Lately, we have studied invertebrate animals

that have circulatory systems, respiratory systems, or both:

Mollusca Annelida Arthropoda

Common Name Mollusks Segmented Worms Arthropods

Key Characteristic / innovation

Mantle and CaCO3 shell

Segmented, softbodied

exoskeleton

Circulatory System Open Closed Open

Respiratory System gills Diffusion / skin Gills or book lungs

Important Classes Cephalopods, Gastropods,

Bivalves

n/a (several) Crustacea, Insecta, Arachnida, Myriapoda

Two Phyla Left• Phylum Echinodermata includes the starfish, and is

our next topic.

• Phylum Cordata includes everything with a backbone, and will be a separate unit. It includes– Mammals, Birds, Reptiles, Fish, Amphibians

A quick introduction to the Echinodermata • Includes starfish, sea urchins,

sand dollars, and others.

• Name means “spiny skin”

• Important to marine ecosystems (only major phylum which includes NO species that live on land or in fresh water)

Some Key Characteristics

• Calcitic, mesodermal endoskeleton. (translation: Many tiny calcium-based bones in their skin)

• Pentaradial symmetry.

• Water-based vascular system

Organizing the Phyla

• Kingdom Animalia can be divided into several Subkingdoms or Superphyla – cladistic groups between a kingdom and a phylum

• Kingdom>Subkingdom>Superphylum>Phylum>Subphylum>Superclass>Class… etc. etc.

Subkingdoms Metazoa and Parazoa

• The subkingdom Metazoa (“upper animals”)includes all animals that have tissues that carry out different functions.

• The subkingdom Parazoa (“beside the animals”) includes Phylum Porifora and a few other minor phyla (remember – we’re only looking at the “big 9” animal phyla)

Superphyla Radiata and Bilatera

• The subkingdom metazoa is further divided into 2 superphyla: Radiata and Bilaterata, based on body symmetry.

• Echinoderms are in superphylum bilaterata even though they are pentaradial– Evolved from bilaterans– Have bilateral larval stage

Protostomes vs Deuterostomes• Protostomes and

deuterostomes are two groups of animals (superphyla to be specific) organized by the following:– Protostomes have

ventral nerve cords, Deuterostomes have dorsal nerve cords

– Embryological development is different:

Word Meanings

• Protostome: “first mouth”• Deuterostome: “second mouth”

The big ideas

• Phylum echinodermata includes starfish and other organisms that are very distinct from other invertebrates

• Subkingdoms Parazoa vs. Metazoa• Superphyla Radiata vs. Bilaterata• Superphyla Protostomata vs. Deuterostomata• Enchinoderms are more closely related to

chordates than any other invertebrates.