bio 4

Arthropod Structure

Division of tissues (endoderm, mesoderm, ectoderm), bilateral symmetry, a coelom, and segmentation.

Metamerism

Repetition of body segments.

Tagmata

Functional groups formed by the fusion of individual segments during embryological development.

Coelom

A body cavity; in arthropods, it is an open circulatory system.

Exoskeleton

The outer protective layer of arthropods composed of two layers (epicuticle and chitin).

Ocellus

A simple eye that detects light intensity and motion.

Compound Eye

An eye that detects movement and can form primitive images.

Cephalothorax

A fused structure of the head and thorax in some arthropods.

Chelipeds

The first pair of legs in crayfish, used for defense and capturing prey.

Swimmerets

Appendages found on the abdomen of crayfish that help in respiration and brood eggs.

Asteroidea

A class of echinoderms that are usually pentamerous, have spiny skin, and tube feet confined to ambulacral grooves.

Ophiuroidea

A class of echinoderms characterized by thin, mobile arms, typically pentamerous.

Echinoidea

A class of echinoderms that includes sea urchins and sand dollars, lacking arms.

Aristotle's Lantern

A feeding device found in all forms of Echinoidea.

Sea Cucumbers

Echinoderms with bilateral symmetry, no arms, and a whorl of tentacles around the mouth.

Sand Dollar Oral Side

Contains mouth for food, food grooves for capturing particles, and anus for gas exchange.

Sand Dollar Aboral Side

Contains gonopores for gamete release, petaloid respiratory surfaces, and madreporite for water entry.