Bio 2 lab: excerise 22 Annelids

Define metamerism

Segmentation
body is divided into repeating segments called metameres or somites

List 5 advancements seen in annelids

— true body cavity
— 2 muscle layers: circular and longitudinal
— nervous system with a solid nerve cord
— Closed circulatory system; blood stays inside the vessels
— Complete digestive tract— food from mount to anus

what are the 3 class of annelids

polycheata
oligochaeta
hirudinea

polychata

mainly marine worms
clam worms

Oligochaeta

worms living in freshwater and moist soil, including earthworms

hirudinea

Leeches; inhabits fresh and marine waters

4. State the phylum, class, genus, and species of the earthworm.

• Phylum: Annelida

• Class: Oligochaeta

• Genus: Lumbricus

• Species: Lumbricus terrestris — the specific epithet is terrestris.

State the type of circulatory system of the earthworm.

Earthworms have a closed circulatory system, meaning blood circulates within vessels.

• Dorsal blood vessel: carries blood anteriorly, toward the front.

• Ventral blood vessel: carries blood posteriorly, toward the back.

• Aortic arches (“hearts”): connect the two main vessels and pump blood.

7. State the organ of excretion of the earthworm.

The excretory organs are nephridia—small, coiled tubes. According to your reading, a pair occurs in each segment except the first three and the last.

Describe the earthworm's structure.

Each nephridium has:

• Nephrostome: a ciliated, funnel-shaped opening into the body cavity.

• Tubule: carries and processes the fluid.

• Nephridiopore: an external opening through which waste exits.

Identify the earthworm as monoecious (hermaphrodite) and describe its reproduction.

Earthworms are monoecious, or hermaphrodites, meaning each individual has both male and female reproductive organs. They reproduce through cross-fertilization with another earthworm

describe earthworm reproduction.

• Two earthworms align and exchange sperm.

• Each stores its partner’s sperm in its seminal receptacles.

• The clitellum secretes a mucous tube that slides toward the anterior end, collecting eggs and the stored sperm.

• Fertilization occurs within this tube, which forms a cocoon.

• The young develop inside the cocoon and eventually hatch.