Ecdysozoa and Their Characteristics

Study Notes

Ecdysozoa

Ecdysozoans shed their exoskeletons (ecdysis)
Two phyla studied: Nematoda (roundworms) and Arthropoda (insects, spiders, crustaceans)

Nematoda vs. Annelida

Nematodes lack the segmented body and coelom of Annelida (segmented worms).

Arthropod Body

Composed of segments
Exoskeleton for support and protection

Arthropod Appendages

Modified for various functions (e.g., locomotion, feeding, sensory)

Open vs. Closed Circulatory Systems

Open: Blood not always contained in vessels
Closed: Blood always in vessels
Arthropods have open circulatory systems.

Millipedes vs. Centipedes

Millipedes have two pairs of legs per segment
Centipedes have one pair of legs per segment

Insect Success

Flight and complete metamorphosis are key factors enabling insects to thrive

Incomplete vs. Complete Metamorphosis

Incomplete: Gradual change in form
Complete: Distinct larval, pupal, and adult stages.

Crustaceans

Belong to the phylum Arthropoda
Examples: Crabs, lobsters, shrimps

Deuterostomia

Includes echinoderms (e.g., sea stars) and chordates (e.g., vertebrates)

Sea Star Body Plan

Radial symmetry
Water vascular system for locomotion, feeding, and respiration. Water vascular system is unique to echinoderms

Sea Star Tube Feet

Used for locomotion, capturing prey, and attachment.

Echinoderms

Examples: Sea stars, sea urchins, brittle stars, sea cucumbers.

Description

Explore the fascinating world of Ecdysozoa, focusing on the two main phyla: Nematoda and Arthropoda. Understand the differences between nematodes and annelids, as well as the various circulatory systems and body structures in arthropods. Test your knowledge on insect success and the stages of metamorphosis.