1. BIOLOGY Unit 7: Earthworm Notes

2. (1) External Parts Setae: Clitellum: Mouth vs. Anus: Rings / Segments
Contain tiny hairs to help with movement + sex.
Clitellum:
Knob near center-length of worm.
Secretes fluid to enclose fertilized eggs.
Mouth vs. Anus:
Mouth = Closer to Clitellum
Anus = Further away from Clitellum

3. *MOST INTERNAL PARTS ARE BETWEEN THE MOUTH + CLITELLUM.*
Ganglia:
Fleshy bit right behind the mouth.
“Brain” of worm.
Aortic Arches:
Tiny black, finger-nail looking bits.
Circulate blood / nutrients.

4. (3) Digestive Organs Pharynx: Esophagus: Crop: Gizzard:
Round Bump behind mouth + ganglia.
Starts to break down food.
Esophagus:
Wrinkly tube leaving the mouth + pharynx.
Carries food to next organs.
Crop:
Round lump after esophagus.
Stores food before digestion.
Gizzard:
Round lump after crop.
Contains stones to break apart food.

5. Digestive Organs (Cont’d)
Intestine:
Long skinny tube leaving gizzard.
Goes rest of length of worm.

6. (4) Reproductive Organs
Seminal Receptacles:
Fleshy colored lumps/bits, behind the hearts.
Receive sperm for egg fertilization.
Seminal Vesicles:
Small fleshy lumps/bits, behind hearts.
Release + store sperm.

10. ---Dissection Notes---
Lie worm on its belly (rounded/darker side pointed up).
Identify clitellum.
Carefully cut from MOUTH  CLITELLUM
Carefully peel back skin.
Identify organs.

11. Dorsal Blood Vessel (Dark Line)
External Dorsal:
Mouth
Clitellum
Dorsal = top (like dorsal fin) more commonly called posterior today.
Blood Vessel = carries blood….
Dorsal Blood Vessel (Dark Line)
Anus

12. External Ventral: Mouth Sperm Ducts Clitellum Genital Setae
Clitellum: Produces mucus for reproduction
Mouth is always closest to clitellum, anus is at the other end.
Genital Setae: used to hold the worms together during mating.
Sperm Ducts: Produce sperm.
Female Genital Pores: contain egg.
Worms are hermaphrodites, but only reproduce through sexual reproduction. This allows all worms to reproduce, increasing chance of successful offspring.
Sperm Ducts
Clitellum
Genital
Setae
Female Genital Pores

13. Internal: Pharynx Esophagus Ganglia (Brain) Crop Aortic Arches
Right Side = Mouth
Cut open dorsal side (top)
Ganglia = Brain
Pharynx = food tube  esophagus
Esophagus  food tube  crop (goes underneath the heart and repr. Organs)
Crop = storage unit
Gizzard = stones + muscle contraction breaks down instestine
Intestine = useful nutrients absorbed, waste  out anus
Earthworms have 5 aortic arches (5 hearts)
Oxygen diffuses directly from air  skin  blood stream
Esophagus
Ganglia
(Brain)
Crop
Aortic Arches
Intestine
Gizzard
Seminal Vessicles
Seminal Recepticles

14. Internal w/o Digestive…
Nerve Cord (Like our Spinal Cord)
Seminal Receptacles