Earthworm%20dissection

1
Earthworm dissection

• Lumbricus terrestris
• Phylum -AnnelidaClass - Oligochaeta Family
  -LumbricidaeGenus -LumbricusSpecies -
  terrestris

2
http//www.ncsu.edu/scivis/lessons/earthworm/Overv
iew.html

• http//www.usd267.com/TL20Student20Pages/8th20S
  cience20Teacher20Resources.html

http//yucky.discovery.com/flash/worm/
3
Background 

• Among the most familiar invertebrate animals are
  the earthworms, members of the phylum Annelida.
  The word annelida means "ringed" and refers to a
  series of rings or segments that make up the
  bodies of the members of this phylum.

4
(No Transcript)
5
(No Transcript)
6
Internally, septa, or dividing walls, are located
between the segments. There may be more than 100
segments in an adult worm.
7

• The clitellum is a swelling of the body found in
  sexually mature worms and is active in the
  formation of an egg capsule, or cocoon.

clitellum
8
Reproductive system

• Eggs are produced in the ovaries and pass out of
  the body through female genital pores. Sperm are
  produced in the testes and pass out through tiny
  male genital pores. During mating, sperm from one
  worm travel along the sperm grooves to the
  seminal receptacles of another worm.
  Fertilization of the eggs takes place outside the
  body as the cocoon moves forward over the body,
  picking up the eggs of one worm and the sperm of
  its mate.

9
(No Transcript)
10
Seminal Receptacles
11
Seminal Vesicles
12
Circulatory system

• The pumping organs of the circulatory system are
  five aortic arches.

13

• Circulatory fluids travel from the arches through
  the ventral blood vessel to capillary beds in the
  body. The fluids then collect in the dorsal blood
  vessel and reenter the aortic arches.

14
Dorsal Blood Vessel
15
Digestive system

• The earthworm takes in a mixture of soil and
  organic matter through its mouth, which is the
  beginning of the digestive tract. The mixture
  enters the pharynx, which is located in segments
  16.

16
pharynx
17

• The esophagus, in segments 613, acts as a
  passageway between the pharynx and the crop. The
  crop stores food temporarily.

18
Crop
19

• The mixture that the earthworm ingests is ground
  up in the gizzard. In the intestine, which
  extends over two-thirds of the body length,
  digestion and absorption take place. Soil
  particles and undigested organic matter pass out
  of the worm through the rectum and anus.

20
Gizzard
21
(No Transcript)
22
Nervous System
The nervous system consists of the ventral nerve
cord, which travels the length of the worm on the
ventral side, and a series of ganglia, which are
masses of tissue containing many nerve cells.
23
Ventral Nerve Cord
24

• The nerve collar surrounds the pharynx and
  consists of ganglia above and below the pharynx.
  Nervous impulses are responsible for movement and
  responses to stimuli. Each segment contains an
  enlargement, or ganglion, along the ventral nerve
  cord. Excretory functions are carried on by
  nephridia, which are found in pairs in each body
  segment. They appear as tiny white fibers on the
  dorsal body wall.

25
Respiration

• The earthworm has no gills or lungs. Gases are
  exchanged between the circulatory system and the
  environment through the moist skin.

26
(No Transcript)
27

• Color the digestive structures blue
• Color the circulatory structures red
• Color the reproductive structures purple
• Possible quiz questions
• 1. Describe the external body of the earthworm.
• 2. How can you tell ventral from dorsal?
• 3. Where are the setae and how many are there?
• 4 What do you need to avoid cutting when making
  the first cut?
• 5. What is the body cavity called?
• 6. List the order that thing pass as going
  through the digestive system of the worm?
• 7. Label a diagram of the ventral side of the
  worm and label the mouth, prostomium, setae,
  sperm groove, openings of seminal receptacles,
  male genital pore and clitellum
• 8. Briefly describe the systems of the earthworm
• Digestive, Circulatory, respiratory, reproductive
• 9. Be able to label the parts of the internal
  and external structures.

28

• 1. Describe the external body of the earthworm.
• 2. How can you tell ventral from dorsal?
• 3. Where are the setae and how many are there?
• 4. Draw a diagram of the ventral side of the
  worm and label the mouth, setae and clitellum.
• 5. What do you need to avoid cutting when making
  the first cut?
• 6. What is the body cavity called?
• 7. What are the compartments called?
• 8. List the order that thing pass as going
  through the digestive system of the worm?
• 9. Briefly describe the systems of the earthworm
• Circulatory, respiratory, reproductive
• 10. Be able to label the parts of the internal
  and external structures. Label a diagram
• color code the systems