Biology:Chapter 28 Section 2:Groups of Arthropods

By: Adam GoetschPeriod 33/29/09

Crustaceans

• Crustaceans are in the subphylum Crustacea• They typically have two pairs of antennae, two or three

body sections, and chewing mouthparts called mandibles.

Body plan:- Cephalothorax - formed by fusion of the head with the

thorax- Thorax –lie behind the head and houses most of internal

organs- Abdomen – the posterior part of the body- Carapace – part of the exoskeleton that covers the

cephalothorax

Crustaceans (continued)

Body plan (continued):- Mandibles – a mouthpart adapted for biting and

grinding food.- Gills attached to the appendages associated

with the cephalothorax- Chelipeds – bear large claws that are modified

to catch, pick up, crush, and cut food (behind the claws are four pairs walking legs).

- Swimmerets- are flipper-like appendages used for swimming

Spiders and Their Relatives

• Horseshoe crabs, spiders, ticks, and scorpions are members of the subphylum Chelicerata.

• Chelicerates have mouthparts called chelicerae and two body sections, and nearly all have four pairs of walking legs.

• Body plan: Chelicerae- mouthpart that contains fangs and

are used to stab and paralyze prey Pedipalps- longer than the chelicerae and are

usually modified to grab prey

Horseshoe Crabs

• Are the oldest living arthropods

• First appeared 600 million years ago that haven’t evolved much

• Closest relatives are spiders, but heavily armored bodies like crabs

• Has long tail used for movement

• Get as big and shape of a large frying pan

Spiders

• Feeding: from small birds to other arthropods, some use webs and others stalk and pounce.

• Spiders can’t swallow unless food is liquefied and they inject their prey with paralyzing venom.

• When paralyzed the spider then injects digestive enzymes that break down tissues the prey’s tissues.

Mites and Ticks

• They are often parasites.• Chelicerae and Pedipalps are meant for digging

into the host’s tissues and sucking out their blood or plant fluids

• Pedipalps are often used to attach to the host.• Example of Mites: kill houseplants and major

agricultural crops like cotton• Example of Ticks: bring serious diseases such

as Rocky Mountain spotted fever or Lyme disease.

Scorpions

• Habitat: warm area such as deserts.

• Have long segmented abdomens that carries a venomous stinger that can kill or paralyze prey.

• Scorpions chew prey unlike spiders.

Insects and Their Relatives

• Belong to the subphylum Uniramia• Examples of Uniramia: centipedes, millipedes,

and insects• Uniramians have jaws, one pair of antennae and

unbranched appendages• Centipedes: worm- like bodies with 100 pairs of

legs, class of chilopoda• Millipedes: worm- like bodies with double the

pairs of legs and body segments then the centipedes