Chapter 26 Arthropods and Echinoderms

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Phylum Arthropoda

Latin for "Jointed Legs"

Arthropod features

segmented invertebrates with bilateral symmetry and coelomate body cavity.

head

mouth parts for feeding and various types of eyes

Thorax

middle body region to which legs and wings are attached.

abdomen

posterior body region: contains digestive structures and reproductive organs.

Arthropod exoskeleton

hard thick outer covering made of chitin.
protects and supports internal organs and tissues.

disadvantages of arthropod exoskeleton

relatively heavy so keeps size small in order to grow must molt.

molting

shedding and replacing exoskeleton

Appendage

any structure like a leg or antenna that grows out of body of animal.

advantages of appendages

allow flexibility and variety of functions and movements.

Feeding and digestion: arthropod

complete one way digestive system from mouth to anus.

gills

feathery structures used by aquatic arthropods for oxygen and carbon dioxide exchange found in crustaceans.

tracheal tubes

system of branching tubules carrying oxygen through body found in most insects.

book lungs

air filled chambers hat look like pages in a book: spiders.

Malpighian tubules

remove cellular wastes from blood.

Circulation in arthropods

open circulatory system

reproduction of arthropods

sexual with separate sexes.

compound eye

multiple lenses that detect movement and color.

simple eye

1 lens that detects light.

antennae

stalklike structure that detect changes in environment (movement and sound)

tympanum

hearing membrane

Class Crustracea

crayfish,lobsters. 2 pairs of antennae. first pair of legs are chelipds. large claws. swimmerets.

chelipeds

Claws. adapted to crush and catch food.

swimmerets

appendages used for reproduction and swimming.

Class Arachnida

spiders,scorpians, mites,ticks. 2 body regions (cephalothorax and abdomen) 4 pairs of walking legs. no antennae. chelicerae.

Chelicerae

modified pinches/ fangs for holding food or injecting venem.

spiders

capable of constructing specific kinds of webs with spinnerets

spinnerets

allow spiders to spin silk from silk glands.

class Merostomata

horseshoe crab..living fossils have remained unchanged for 20 million years.

class insecta

largest, most diverse group of arthropods. successful b/c of adaptions. can live many places. flies,butterfly.

Metamorphosis

change in body shape and form in development.

complete metamorphosis

4 stages: Egg, Larva, Pupa, Adult. most insects. butterflies.

Larva

wormlike, eats grows and molts.

Pupa

resting stage surrounded by cocoon.

incomplete metamorphosis

hatch from eggs as nymphs: grasshoppers. cockroaches.

nymphs

look like miniature adults but lack wings and mature sex organs.

Class Chilopoda

carnivores with flattened wormlike bodies
Centipedes

centipedes

have long, segmented bodies, each segment has one pair of jointed legs.

Class Diplopoda

scavengers with cylindrical bodies. Millipedes.

Millipeda

have two pairs of appendages per body segment.

Phylum Echinodermata

Greek: "Spiny Skinned", all are marine, radial symmetry as adults. larvae have bilateral.

Echinoderm endoskeleton

consists of calcium carbonate spiny plates covered by a thin layer of skin.

Pedicellariae

pincer like appendages on spines of sea starts and sea urchins. catch food, protect. clean body.

Water Vascular system def:

system of fluid filled, closed tubes that work together enabling echinoderms to move and get food.

Madreporite plate

sieve-like, disk shaped opening on upper surface of body. water enters and leaves through this.

Ampullae

contract and squeeze water into tube feet

tube feet

hollow, thin walled tubes ending in suction cups. movement by pushing out and pulling in tube feet.

Sea star

5 arm arranged around a central disk, if rays are lost can be replaced through regeneration.

Brittle Stars

Most brittle stars have five arms. Arms are thin and very flexible.

Water vascular system path

madreporite plate--stone canal--ring canal--radial canal--ampullae--tube feet.

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