means "little rings"
have cylindrical bodies which are divided into seguments
thin skin called epidermis
Gases are exchanged
through the thin epidermis and carried to the animal's tissues by tiny blood
The epidermis is
covered with a thin, protective cuticle which must be kept moist to
permit its passage of oxygen through it.
by body covering - cuticle
movement: 2 muscle layers work together for forward movement:
- contract and make worm longer and thinner
contract and draws posterior end forward.
are tiny bristles that anchor the worm
mouth - where food enters
anus - where nondigested food leaves
digestion: the process of breaking food
(2) Chemical digestion:
the breaking down of food into substances usuable by cells
crop- temp. stored
gizzard- grinds the food
by mechanical digestion
digestion and absorbtion
The mouth of the earthworm secretes fluids that moisten the soil
as it enters the earthworm
food-laden soil is drawn into the mouth through the muscular pharynx
and passed down the esophagus to the crop, where it is temporarily
food is passed into the gizzard where muscular contractions grind
the food against the soil and break the food into small pieces
food is then digested in the intestine, where digestive enzymes
break it down (this is chemical digestion)
the intestinal tract is straight and tubular; food is absorbed by blood
circulating through its walls and indigestible materials are expelled through
the anus. These solid wastes
are called casts (or castings). This enriches and improves the soil.
The burrows dug by earthworms permit the passage of
The feeding process of a single earthworm will produce approximately 1/2
pound of rich, fertile humus in one year.
An estimated 18 tons of earth per acre per year is brought up from below
and deposited on the surface by earthworms.
earthworms, found in tropical regions, may be 12 ft. long and have 500 segments.
They are located by the gurgling sounds they make as they move underground.
The earthworm has no
special respiratory organs.
Gas exchange is made through
the moist skin by diffusion.
outer surface must remain moist
if an earthworm is dried by the sun, it will die of suffocation
if they remain in water-soaked earth, they will drown
the movement of substances throughout the body of an organism.
red blood (contains
major blood vessels (dorsal and ventral)
major pairs of aortic arches
Closed circulatory system:
a type of circulation in which the blood remains in vessels
Dorsal blood vessel:
it is the pumping organ (acts as the heart)
pumps blood forward to the
5 pairs of aortic arches
chief function - maintain a steady pressure of blood into the ventral
Blood passes through
the aortic arches down to the
Ventral Blood Vessel:
(serves as the aorta) receives blood
the removal of wastes from an organism's body.
The organs of excretion are the nephridia, a pair which are
tiny looped tubes that collect wastes from the
Wastes are collected in the nephridia and are passed out of
Most animals control their bodies through neurons.
bundle of neurons wrapped in protective coverings
cluster of nerve cells (acts as a relay station)
a mass of nerve tissue;
sometimes called a simple
organ that coordinates the bodily functions
anything that causes a response in an organism
EARTHWORM'S NERVOUS SYSTEM
receptors are distributed over the animal's entire body.
a structure that can sense a stimulus
They are sensitive to light, touch, and
travels from sensory receptor (in front) to two large ganglions in the
receptors in other areas carry impulse to the nerve cord along nerve cord
there is one small ganglion in each segment;
inside the ganglions the impulses are transferred to the proper neurons;
neurons carry impulses to muscles, bristles, etc.
ganglia in 3rd segment (a mass of nervous tissue)
double ventrical nerve cord with smaller ganglia- 1 for each segment
nerves leading to muscles and sensory structures
(light, touch, certain, chemicals, and
normal mode is sexual (some species can regenerate)
male organs are
testes (2 pairs) in 10th and 11th segments
are ovaries (1 pair) in the 13th segments
reproduction, the 2 worms must exchange sperm.
earthworms, found in tropical areas, may be 12 ft. long and have 500 segments. They are located by the gurgling sounds they make as they move underground.