Earthworm Lubricus terrestris Phylum: Annelida
1. Similar body segments- bilateral symmetry
2. Epidermis - forms the skin, protection
3. Coelom- body cavity
4. Complex organ systems
5. Hermaphrodites- copulation: transfers sperm cells to pouch of other worm; young
worms develop inside a cocoon that is secreted by the clitellum
Segment 14- pores for eggs Segment 15- pores for sperm
6. Food- decaying vegetation, animal matter; eat way through soil
**Makes soil porous so air can reach plants
7. Tube within a tube
Alimentary canal – tube through which food passes
(peristalsis-rhythmic contractions)
Digestive glands
8. Circulation- blood, closed circulatory system like humans
Main vessels:
A. Dorsal (upper) blood vessel-carries blood forward
B. Ventral (lower) blood vessel – carries blood toward rear
C. 5 pairs aortic arches encircle esophagus – hearts, pump blood; push blood into the
dorsal artery from the ventral part of the body
D. Capillaries- exchange between blood and cells
Oxygen and carbon dioxide exchange at skin
Wastes- excretory system
Blood red but NO red blood cells, pigment distributed
9. Excretion – nephridia (pairs of tiny, coiled, white tubules found in all body segments
except the first 3 and the last) excretes nitrogenous wastes (ammonia, urea, mineral
salts)
Carbon dioxide diffuses from blood through skin
10.Regulation – central nervous system: simple dorsal brain (solid large ganglia) and a
pair of solid ventral nerve cords that enlarge into ganglia
ganglia- tiny nerve control centers; swellings visible in each segment that relay
and coordinate reflex movements
ventral nerve cord-motor function is to carry impulses for movement; sensory
function is to carry impulses to the brain from parts of the body
11. Locomotion – setae bristles, 4 pairs on each segment
Holes are made in the soil through which air and water can penetrate.
12. Respiration - diffusion-skin
Oxygen carried by blood to cells
Hemoglobin dissolved in blood (In red blood cells in humans)
Moist, external respiratory system
Anterior to posterior: Prostomium (anterior tip), brain, pharynx (sucks food), esophagus (carries food) and aortic arches (heart), seminal receptacle (receives sperm), seminal vesicle (also called sperm vesicle; produces and stores sperm), ovary, crop (stores food), gizzard (grinds food), intestine (absorbs digested foods; enzymes secreted for chemical digestion), clitellum (secretes a cocoon around fertilized eggs)
Dissection Review: Go to the following website.