Transcript Segmented Worms

Segmented Worms
SWBAT describe the body covering, method of
support, and forms of movement used by the
earthworm; describe the nervous system of the
earthworm; identify the structures of an earthworm’s
digestive system and describe the functions of each
structure; explain the processes of circulation,
respiration, and excretion in the earthworm; define
closed circulatory system; evaluate the significance
of having earthworms in the soil.
Segmented Worms
 What phylum does the earthworm
belong in?
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Annelida
 Segmented
Body of an Earthworm
 Epidermis
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Its skin, through which gases are
exchanged
 Cuticle
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Thin outer coating that protects it from
harmful parasites and substances
Body of an Earthworm
 How do earthworms move?

An earthworm has two muscle groups that
contract and expand its body. It anchors
itself using the bristles on its body and then
contracts, anchors its other end and
releases the front to expand and move
forward.
Intestines of the Soil
 How do earthworms help the soil?

Earthworms digest plant and animal matter
so that it becomes usable for plants to
gather nutrients from the soil. They also
bring soil that is deep, up toward the
surface as they burrow, which can affect
crop growth.
Earthworm’s Nervous System
 Sensory receptor

A structure that can sense a stimulus and
then start an impulse traveling along a
nerve
 Describe the nervous system of an
earthworm.

They have sensory receptors that send
impulses through the nerve cord to the
ganglia that tell it how to respond.
Earthworm’s Digestive System
 Describe the process of digestion in an earthworm.
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Soil enters through the mouth and into the pharynx,
where glands secrete a liquid to lubricate it as it passes
through.
The esophagus is a tubular passageway that then
carries the food to the crop that stores it temporarily.
Food then passes into the gizzard which mechanically
digests food by contracting and relaxing.
The ground up food passes to the intestine where
digestive enzymes break the food into a soluble
substance that is absorbed into the bloodstream to be
distributed to the cells.
The indigestible parts leave through the anus, and are
called castings.
Earthworm’s Circulatory
System
 Closed circulatory system

Blood never leaves the vessels
 Aortic arches


Same function as a heart
Control blood pressure
 Capillaries

Tiniest blood vessels – pass blood to arteries
 Veins

Vessels that carry blood toward the heart
Earthworm’s Circulatory
System
 Explain the process of circulation in an
earthworm.

The circulatory system is a continues
network of blood vessels. The large dorsal
blood vessel of the earthworm works with
the aortic arches to pump blood and
control blood pressure. The bloodstream
is used to pass substances between an
earthworm’s tissues.
Earthworm’s Respiratory and
Excretory Systems
 Explain the processes of respiration and
excretion in and earthworm
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Earthworm’s exchange gases through its
epidermis (no lungs).
Most of the segments in a worm have a
coil of tubes that collects waste from the
blood and then passes it out through tiny
pores on the surface.