Chapter 33. The Ancestors Protists: Choanoflagellates

Chapter 33

The AncestorsProtists: Choanoflagellates

The AncestorsColonies of choanoflagellates

The AncestorsColonies of choanoflagellates

Porifera – The Sponges

Porifera – The Sponges

Sessile filter feederGrouped based on

“skeleton” type.Can form

gemmules for protection.

Porifera – The Sponges

AsymmetricalNo tissue layers.

Porifera – The SpongesSexual

reproduction - hermaphrodites

Can grow whole new sponges if cut in pieces

CnidariaExamples: jellyfish, anemones, hydra and

coral

CnidariaNamed for cnidocytes

CnidariaDiploblasticTwo body forms: polyp & medusaGrouped based on amount of life spent as

polyp or medusa

Cnidaria

Reproduces asexually by budding.

Cnidaria

Platyhelminthes - FlatwormsExamples: planaria, liver flukes, tapeworms

Platyhelminthes - Flatworms

Most are parasitic

Platyhelminthes - Flatworms

Bilateral symmetry

Simplest phylum with a head

Simple organ systems

Reproduce sexually and asexually

Platyhelminthes - FlatwormsAcoelomatesTriploblastic

RotiferaNamed for feeding rotorsPseudocoelomatesHave an anus!

Images from http://www.microscopy-uk.org.uk

RotiferaUsually reproduces by parthenogenesis

Nematoda – RoundwormsFound in most aquatic habitats, soil, and in

plant and animal tissues

Nematoda – RoundwormsMany are parasitic – hookworms,

roundworms, pin worms, heartworms, etc.

Nematoda – RoundwormsPseudocoelomates

Simple organs

Annelida – Segmented WormsExamples: earthworms, fireworms, leeches

Annelida – Segmented Worms“Little rings” –repeating segments, some

specializedCoelomates

SetaeParapodia

Annelida – Segmented WormsFairly complex anatomy

MolluscaLargest classes:

GastropodsBivalvesCephalopods

MolluscaMuscular foot

MolluscaHead

MolluscaVisceral mass

Arthropoda“Jointed foot”

ArthropodaMost successful animal phyla – 67% of all

species!

ArthropodaFour main groups:

CheliceriformsMyriapodsHexapodsCrustaceans

ArthropodaExoskeleton - ecdysis

ArthropodaOpen circulatory system

ArthropodaTracheal tubesSpiracles vs. book lungs

ArthropodaMalpighian tubules

Echinodermata“Spiny skin”

EchinodermataRadial symmetry

EchinodermataWater vascular systemTube feet

EchinodermataNo head or brainSimple anatomyDeuterostomesEndoskeleton