Arthropods and Echinoderms Chapter 7. Review What Invertebrates have we learned about so far? Porifera – sponges Cnidaria – jellyfishes, sea anemones,

Arthropods and Echinoderms

Chapter 7

Review• What Invertebrates have we learned about so

far?• Porifera

– sponges

• Cnidaria – jellyfishes, sea anemones, coral

• Ctenophora – comb jellies

• Molluscs – snails, bivalves, octopuses, squid, cuttlefish

Objectives

1. Explain the basic characteristics of arthropods

2. Differences between copepods, barnacles, krill, and decapods

3. Explain the body structure of echinoderms

There are a lot of them!

• Largest phylum on earth

• 1,000,000 + species and several million undiscovered

• 3 out of every 4 animals on earth are arthropods

• The largest group are the __________?

• Insects!

Arthropod Characteristics

• Exoskeleton:– Tough, non-living

external skeleton– Made of chitin– Protection, support,

flexibility

• Segmented, bilaterally symmetrical body

Marine Arthropods

• Majority of marine arthropods are crustaceans

• Barnacles, shrimps, lobsters, crabs, and a variety of others

Crustaceans: Copepods

• Use mouth parts to capture food

• zooplankton• Large antennae used to

swim

Crustaceans: Barnacles

• Filter feeders• Usually attached to

surfaces (whales and crabs and rocks)

• Bodies enclosed by heavy plates

• Use cirri to sweep the water and feed

Crustaceans: Krill

• Most numerous animals on earth

• Exceed total human weight on the planet

• Major piece of the marine food chain

Crustaceans: Decapods (10 legs)

• Largest group of crustaceans (10,000 species)

• Includes shrimp, lobsters, crabs

• Largest crustaceans in size

14 lb Alaskan King Crab

Echinoderms• Sea stars, sea urchins, sea cucumbers, and others• Radially symmetrical

– No head!• Have an endoskeleton

– Skeleton secreted within tissues (like ours)• Water vascular system

– Network of water filled canals

Tube Feet

• Tube feet are muscular extensions of water canals

• Used for attachment, locomotion, reception of chemical and mechanical stimuli, and eating.

Sea Urchins

• Round, rigid shell• Movable spines• Sucker-tipped tube feet

– Breathe through these via gas exchange—no gills or lungs

– Use to pass prey down back to mouth

• Mouth on bottom and anus on top

Sea Urchins• Aristotle’s lantern

– Jaws in the mouth– 5 teeth, self-sharpening– Able to dig holes in stones to

use as hideaway• Behavior can signal poor water

quality– Lack of movement and

drooping spines• High intensity grazers

– They love algae and kelp• Sea Otters help protect kelp

forests from destruction• Sea Urchin Sex

Sand Dollar• Adapted to live in sandy bottoms• Deposit feeders• Is this one dead or alive?

Sand Dollar• Have tube feet• Adapted to living in soft

bottoms by having flattened bodies and short spines

• Has a less developed Aristotle’s Lantern– Feed on small particles– 5 doves

• Chews food for up to 15 minutes before swallowing– Takes up to two days to

digest

Sunflower starfish

• 24 arms– Juveniles start with 5

• Fast! 40 inches per minute

• 15,000 tube feet• Up to 1m (39 in) across• Can swallow an entire

urchin, digest it, and expel its test (skeleton)

Video Footage of CA Coast