Bio 94 Midterm 2

have an enclosed body cavity completely lined with mesoderm

have no enclosed body cavity

have an enclosed body cavity partially lined with mesoderm

• ex. Sponges
• No plane of symmetry
• Lack nerves, muscles
• Several cell types
• Suspension feeders
• Sexual and asexual reproduction

• ex. jellyfish and coral
• radial symmetry
• 2 germ layers
• First true Hox genes
• Nerves and muscle-like tissue

• ex. Flatworms
• lost coelom
• Free living and parasites
• no structures for gas exchange or circulation
• Head ganglion, longitudinal nerve cord

• Coelom
• Segmented worms (repeated body structures)
• Bristles (chaetae)

• Coelem reduced
• Common traits:
• -- foot
• -- mantle
• -- visceral mass
• -- radula

• Bivalvia (clams, oysters)- Two shells
• Gastropoda (snails, slugs)- Means “belly foot” aka Its “belly” is the foot
• Cephalopoda (octopus, squids)- Means “head foot” aka foot is on its head

(clams, oysters)- Two shells

(snails, slugs)- Means “belly foot” aka Its “belly” is the foot

(octopus, squids)- Means “head foot” aka foot is on its head

parasitic species

• Crustaceans
• Chelicerates
• Insects

• 2 pairs of antenna & 2 body regions (cephalothorax & abdomen)
• ex) crabs

• NO Antennae, 4 pairs of legs, 1 pair of chelicerae (fangs), 1 pair of pedipalps, ONLY a cephalothorax
• ex) spiders, ticks, scorpions

1 pair of antenna, 3 body regions, 1 pair of compound eyes, 1 or 2 pairs of wings, 3 pairs of legs

• star fish
• radial symmetry

• notochord
• ex. fish, humans, cats

looking harmful when its harmless

no holes on side of skull

one hole on side of skull

two holes on side of skull