arthropods and echinoderms chapter 7. review what invertebrates have we learned about so far?...
TRANSCRIPT
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: 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• 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)