1. Animals: Chapter 2: Mollusks, Arthropods, and Echinoderms

2. Mollusks The Octopus—Mollusk Without a Shell
Examples: clams, snails, slugs, octopus
Phylum Mollusca
2nd largest number of species found in phyla
Importance: Used for food, making things, others are parasites

3. The Octopus—Mollusk without a Shell
Eight arms/tentacles
Each with a suction disk to grasp
Able to regenerate tentacles
Hunts for food but otherwise timid
Moves by gliding along on arms
Rapid movement by forcing water through siphon (muscular tube)
May also release black inky substance for quick get away
Soft/Flexible body
Special skin pigments used for camouflage or may also reflect stimulation

4. The Clam—Mollusk with a Shell
Bivalves: two shells
Ex. Clams, muscles, scallops,
Univalve: one shell
Ex. Snail, cochs,
Mantle-think skin that covers soft body; manufactures material for shell
Adds layers as it gets older/grows
Foot- hatchet shaped muscle that moves the clam
Filter Feeders: food found in water
Process:
Sends two siphons into the water
One siphons water into the shell
Inside the shell the water is filtered for food
Second siphon sends water and waste out of the shell

5. siphons
Muscular foot

7. Arthropods
More species than any other animal phylla Insect class is the largest Importance: pollinators, decomposers, crop eaters, disease carriers, and parasites Exoskeleton-hard non-living outer covering Jointed appedages (legs, antennae)

8. A Typical Insect’s Body
3 parts: head, thorax, abdomen
3 pairs of legs—total 6
Most have 2 pairs of wings
Compound eyes

10. Arthropods Insect Life Cycles
Incomplete metamorphosis-several molts-looks the same-sheds old exoskeleton
Incomplete-egg-nymph-adult
Ex. Grasshopper, cockroaches, water-bug, stinkbugs
Metamorphosis-a ‘change in body form’

11. Complete metamorphosis-4 stages-egg-larva-pupa-adult
Larva-active stage (caterpillars, maggots, grubs)
Pupa-resting stage (cocoon, chrysalis, puparium)
Each stage looks different

12. Arthropods Other Interesting Arthropods
Barnacles, crabs, lobsters, shrimp, pill bugs, centipedes, millipedes, scorpions, spiders
Different number of segments and legs
Centipedes-flattened bodies with one pair of legs per segment; hunt for food
Millipedes- rounded bodies with two pair of legs per segment; eat decaying matter

15. Echinoderms Sea stars, sea cucumbers, sea urchins
Body supported by hard flat plates under skin
Plates may have sharp spines
Radial symmetry
Starfish can regenerate rays

16. Water-vascular system key to movement
Rows of tube feet at bottom of each ray
Movement: Attaches tube feet and then pulls body to that location
Eat:
Climbs on top of clam and uses tube feet to pull apart shell
When clam tires the shell opens
Starfish turns its stomach inside out and digestive juices dissolve clam
Starfish then withdraw its stomach from the shell

17. See Flow Charts for
Classes of Mollusks
Classes of Arthropods