Bio Exam 2 PHYLUM: Annelida

Phylum annelida

• “Segmented worms” (metamerism)

• Paired Setae (bristles)

• Cephalization

• Hydrostatic skeleton

Metamerism

Segmented internally and externally

Annelid movement

• Inching, digging, swimming

• Hydrostatic skeleton (no muscles)

• Peristalsis

• Setae prevent backsliding

Peristalsis

The wave-like contraction of a worm

Class Oligochaeta

• Earthworms and freshwater worms

• Clitellum forms egg sac

• Mostly spread by humans

• Alter soil properties and nutrient availability in forests

Class Polychaeta

• Marine worms

• Parapodia and setae function in locomotion and respiration

• Symbiotic feeding

Class Hirudinea

• Leeches

• All carnivorous , some parasites

• Suckers used for feeding and movement

• mostly aquatic, some terrestrial

• can be used for medicinal purposes

Clitellum (Oligochaeta and Hirudinea)

Glandular section of the body wall that secretes a viscid sac in which the eggs are deposited.

Setae (Oligochaeta and Polychaeta)

Bristles that help in locomotion and feeding

Parapodia

Fleshy appendages for breathing and moving

How are earthworms important to soil

• Increased nutrient content in soil

• Remove metals from soils

How are invasive earthworms destructive to some ecosystems

The change in soil concentration and decomposition speed can disrupt natural process of environments not apt to deal with it.