Download Earthworms

JOURNAL #1
• KWL: What do you KNOW about
segmented worms? What do you WANT to
know about segmented worms? What have
you LEARNED about segmented worms?
PHYLUM
ANNELIDA
I. General Information
1. “annelid” means tiny rings
2. Coelomates- true body cavity w/space for
true internal organs.
3. Body is cylindrical & metameric- segmented
4. Bilateral symmetry
5. Closed circulatory system
6. Most have paired setae for movement
II. Class Oligochaeta
1. Earthworms w/ few setae
2. Terrestrial or aquatic
A. Body Structure
1. Prostomium- 1st body segment, overlaps mouth
2. Pygidium- last body segment, overlaps anus
3. Cuticle- tough outer covering for protection
4. Muscles- 2 sets create wave-like motion; longitudinal &
circular
5. Clitellum- band-like structure at anterior end
6. Setae- short bristles on ventral surface that help them
cling to burrows, movement/anchoring
B. Digestion/Feeding
1. Nocturnal- feed at night on leaf litter & soil
(scavengers/decomposers)
2. Mouth- opening to digestive tract
3. Pharynx- acts like pump, pulling food into mouth.
4. Esophagus- tube that leads to crop
5. Crop- storage chamber for food.
6. Gizzard- grinds food before it enters intestine.
7. Intestine- absorbs nutrients from food- has folds called
typhlosole that increase surface area to absorb more
food.
8. Anus- solid wastes excreted here
9. Castings- squiggles of mud on soil surface “worm feces”
Crop
Pharynx
Esophagus
Ventral Nerve Cord
Gizzard
Intestine
C. Excretory System
1. Nephridia- kidney-like organ that consists of
tubes for conducting liquid waste
One per segment
2. Nephridiopores- pores in skin that excrete
liquid waste.
D. Nervous System
1. Cerebral ganglion- bi-lobed simple brain over
pharynx
2. Ventral Nerve Cord- runs length of body on
ventral surface
** Sensitive to touch, light, temp., moisture
E. Respiratory system
• Gas exchange occurs thru diffusion
thru moist skin
F. Circulatory System
1. Closed Circulatory System- blood is
enclosed in blood vessels
2. 5 Pairs of Aortic Arches- enlarged blood
vessels that pump blood thru body
3. Dorsal blood vessel- carries blood to
anterior end
4. Ventral blood vessel- carries blood to
posterior end
G. Reproductive System
1. Monoecious- hermaphrodites
2. Do not self-fertilize
3. Worms line up w/anterior ends away
from each other.
4. Sperm released from seminal vesicles &
is passed along a body groove to the
seminal receptacles
(receivers)
5. Eggs are kept in oviducts until “ripe”
6. After 2-3 hours of copulation,
clitellum forms sticky cocoon.
7. Cocoon passes down body, picking up
egg & sperm
8. Fertilization occurs in the cocoon.
9. Cocoon is deposited in moist soil where
it hatches after about 3 weeks.
Being a hermaphrodite is beneficial to simple
animals because
1. Do not have to search out a specific
mate… can mate with any worm that
comes along.
2. Twice as many offspring can be produced
because both can carry eggs.
Seminal Vesiclesstore worms own
sperm
Seminal Receptacles- receive
sperm from mate
5 Aortic Arches
Nephridia- 2
per segment
for excretion
Dorsal
Blood
Vessel
Cerebral ganglion
III. Class Hirudinea
1.Leeches with no setae
2. Most freshwater, some marine & terrestrial
3.Ectoparasites that feed on body fluid of
host
4.Flattened, segmented
5. 34 segments
A. Digestion/Feeding
1.Anterior & posterior sucker for
attachment to host
2.Jaws slice skin & begin sucking blood.
3. Secrete anesthetic- so you don’t feel bite.
4. Secrete anticoagulant- Hirudin- keeps blood
from clotting while feeding.
5. Engorge until 10x normal size then drop
off
6. Only need to eat every few months.
B. Respiratory/Circulatory/Nervous/Excretory
Same as earthworms
C. Reproductive System
1. Monoecious- hermaphrodites
2. Clitellum is only present during spring
when leeches usually breed
IV. Class Polychaeta
1.Marine worms with many setae
2. Largest class of annelids
3. Live in coral reefs, ocean floor, crevices,
etc
4. Have parapodia which look like paddles along
body
5. Have sensory tentacles called cirri around
mouth.
6. Reproductively- dioecious
V.Economic/Environmental Importance
1. recycle nutrients to soil.
2. burrows aerate & provide space for growing
plant roots.
3. Leeches used for removing excess blood
after surgery for reattachment of
amputated limbs. Body heals faster.
4. Part of food chain
DAILY QUIZ #2
1. The structure used for grinding food in the earthworm is
the
a. Crop
b. Nephridia
c. gizzard
2. Annelida means
a. Soft skin
b. Tiny rings
c. Flat body
3. This phylum of worms is put into different classes based
on
a.
Method of reproduction
b. Type/presence of setae
c. Shape of body
4. The bristle-like structures that help earthworms move are
called
a. Setae
b. Clitellums
5. Earthworms are
a.
Monoecious
b. Dioecious
c. crops
Journal #5
• How are earthworms important to humans
and the environment?
JOURNAL #4
• Explain two ways being a hermaphrodite is
beneficial to the earthworm.
1. Before dissecting, it is necessary for you to
a.
b.
c.
Put on a safety apron
Soak your specimen in preservative
Wash your specimen to remove preservative
DAILY
QUIZ
2. The body covering of the earthworm is best described as
a. Moist cuticle
b. Hard exoskeleton c. Dry & bumpy
3. Leeches
a. Secrete Hirudin b. Secrete anesthetic c. Both A and B
4. The paddle-like setae that are found on the sides of
polychaetes like the clamworm is referred to as
a. Polychaeta
b. Parapodia
c. oars
5. The band-like structure used for reproduction in the
earthworm is the
a. Cuticle
b. Clitellum
c. nephridia
DAILY
QUIZ
#4
1
2
4
3
5
a. Gizzard
b. Crop
c. Nephridia
d. Aortic arches
e. Seminal vesicles
f. Seminal receptacles
Journal #8
• Compare and contrast the digestive systems
of the leech and earthworm.