Chapter 31: Arthropods

Examples: insects, crustaceans, arachnids, centipedes, millipedes

Most diverse phylum

Features of Arthropods

“Jointed” appendagesSegmented body: head, thorax, abdomen, cephalothoraxes – fused head and thorax – (arachnids)

Eyes of Arthropods

Compound eyes – eye with many units

Simple eyes – Single lens, see light and dark only, not image

Exoskeleton

Made of chitinPurpose:

Molting – shedding exoskeleton

Respiration

Varies from group to group.Examples: trachea with spiraclesGills (aquatic)Book lungs (arachnids)

Open Circulatory System

Excretory System

Malpighian tubules – sort of like our kidneys. Structures that filter blood.

I. Arachnids-unique characteristics

Examples: spiders, scorpions, ticks, daddy long legsEight legs2 body segments: cephalothorax, abdomenChelicerae – fangsBreath by using book lungs or tracheal tubes

Unique Feeding of Spiders

Spiders can biteAll have venom Spin web for capture

Brown Recluse

Brown Recluse

Wolf Spider

Tarantula

Camel spider

Scorpions

Poisonous Stinger, Nocturnal

Household Dust mite

II. Insects

Largest group on earth

3 Body sections:– Head – mouthparts,

antennae

– Thorax- 3 pairs of legs

– abdomen – spiracles- organs for breathing, open to tracheal tubes

Insect life cycle

Metamorphosis – physical changeTwo types – complete and incompleteComplete –– 1. Larva– 2. Chrysalis- cocoon– 3. Pupa – inside cocoons– 4. Adult

Pupa stage with chrysalis

Adult stage

Incomplete Metamorphosis

Less of a change 1. Egg2. Nymph – a smaller

version of the adult with no wings

3. Adult

Success of Insects

Found everywhereShort life span, adapt to change quicklyFlight – Elaborate social systems

Head Lice

III. Crustaceans

Examples: crayfish, lobsters, pill bugs, crabs, barnaclesUse gills

IV: Millipedes and centipedes

-1 Pair of legs per segment

-Painful bite

-2 pair of legs per segment

-Herbivores

Ch. 32 Echinoderms

Features of Echinoderms

Spiny, marine invertebratesEndoskeleton – purpose is for protection, muscle attachment– Ossicles with spines

Begin as bilateral, free-swimming larvae

Features of Echinoderms

Radial symmetry as an adult

Water Vascular System

System of canalsUsed for locomotion, feeding and gas exchangeWater flow through canals: – Madreporite– Ring canal– Radial canals– Tube feet – used for

locomotion

Ventral surface of sea star

Additional Characteristics

Nervous system: ring of nerves, eyespotsAbility to regenerate

Diet – hetertrophs: corals, worms, mollusksSome are herbivores

Wrap up

Echinoderms

Seastars Brittle stars Sea urchins Feather Stars

Group 1: Sea Stars

Brittle Stars

Highly flexible arms, no anus, also feet on detritus – bottom dweller, regeneration

Feather Stars

Not sessile, but like to be, sticky arms, nocturnal

Sea Cucumbers

Regeneration of organs, tube feet

Sea Urchins

Scrape algae off of rocks, sponges, tube feet