39 Anthropoda

Arthropods

Most successful animal phylum; 2–10 million species; found in marine, freshwater, and terrestrial environments

Reason for Arthropod Success

Exoskeleton, wings (in insects), and mutualisms with flowering plants

Arthropod Appendages

Jointed appendages used for movement, feeding, defense, and protection

Exoskeleton

Rigid outer covering made of chitin that supports and protects the body

Chitin

Nitrogen

Modified Appendages

Include mouthparts, antennae, and specialized legs

Subphylum Chelicerata

Arthropods with feeding appendages called chelicerae

Class Merostomata

Includes horseshoe crabs (Limulus)

Horseshoe Crab Blood

Contains Limulus Amebocyte Lysate (LAL), used to detect bacterial toxins

Class Arachnida

Includes spiders, mites, and scorpions

Arachnid Body Structure

Cephalothorax and abdomen

Chelicerae

Feeding appendages in arachnids

Pedipalps

Used for sensing and capturing prey

Arachnids Antennae

Absent

Class Crustacea

Aquatic arthropods like crabs, lobsters, shrimp, and crayfish

Crustacean Appendages

Biramous (double

Crustacean Antennae

Two pairs

Crustacean Eyes

Usually compound eyes

Crustacean Mouthparts

Mandibles, maxillae, and maxillipeds

Class Myriapoda

Includes centipedes and millipedes

Myriapod Antennae

One pair

Centipedes

Fast, flattened, carnivorous; live in soil and under logs

Millipedes

Slow, feed on decaying plant material

Class Hexapoda

Six

Insect Body Plan

Head, thorax, abdomen

Insect Legs

Three pairs (6 total)

Insect Wings

Usually two pairs (may vary)

Insect Antennae

One pair

Insect Eyes

Compound eyes and sometimes simple eyes (ocelli)

Insect Success

Due to wings, mutualisms, and diverse mouthparts

Aquatic Arthropod Respiration

Gills

Terrestrial Arthropod Respiration

Tracheal system (air tubes)

Spiracles

Openings that allow air into tracheae

Malpighian Tubules

Excretory organs that conserve water

Why Insects Are Small

Gas exchange relies on diffusion through tracheae