Miller and Levine Chapter 26 Biology

Terms in this set (28)

Structure and Movement
More than 100 segments (virtually identical)
Circular and longitudinal muscles
Worm anchors some middle segments by setae
Contraction of circular muscles elongates segments.
Anterior setae anchor and longitudinal muscles contracts
Feeding and Digestion
Ingest detritus as they burrow
Soil sucked into mouth by pharynx.
The food enters a tube called the esophagus and travels to a temporary storage area called the crop.
The food continues to a part of gut called the gizzard where grinding occurs. This releases and breaks up the organic material.
As the soil passes through the intestine, digested organic compounds and nutrients in the soil are absorbed by the blood.
Elimination of wastes through anus
Circulation
Closed circulatory system
Transportation of oxygen, Carbon dioxide, nutrients, and wastes.
Path of blood
Posterior end via ventral blood vessel
Anterior end via dorsal blood vessel
5 pairs of muscular tubes: Aortic Arches
Contractions of the dorsal blood vessel and the aortic arches force blood through system
Respiration and Excretion
Oxygen and carbon dioxide diffuse through skin and capillaries (small blood vessels)
Exchange of gasses only if skin is moist
Secretions of mucus and a thin cuticle help
Nephridia
Cellular waste excretion and excess water
Each segment (except 1st-3rd and last) have a pair
Neural Control
Chain of ganglia connected by a ventral nerve cord
Most segments have one ganglia and nerves branch from this point
In the most anterior segments, several ganglia are fused to from the "cerebral ganglia"
Processes light, touch, chemicals, moisture, temperature, and vibrations
Reproduction
Hermaphroditic (both sexes)
Cannot fertilize its own eggs.
Mating
Two earthworms press their ventral surfaces together with their anterior ends pointing in opposite directions.
Setae hold worms together
Film of mucus secreted by each worm's clitellum.
Sperm injected into mucus and moves to the seminal receptacle.
Sperm stored and worm separate
Several days later, a tube of mucus and a tough carbohydrate (chitin) is produced by clitellum
Tube slides forward, picks up eggs and sperm then fertilization occurs
Young develop inside the case for 2-3 weeks before hatching
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