BIOLOGY

Unit 7:Earthworm Notes

(1) External Parts• Setae:

– 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

(2) Internal Parts*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.

(3) Digestive Organs• Pharynx:

– 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.

Digestive Organs (Cont’d)• Intestine:

– Long skinny tube leaving gizzard.– Goes rest of length of worm.

(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.

---Dissection Notes---

1. Lie worm on its belly (rounded/darker side pointed up).

2. Identify clitellum.

3. Carefully cut from MOUTH CLITELLUM

4. Carefully peel back skin.

5. Identify organs.

External Dorsal:

Clitellum

Mouth

Dorsal Blood Vessel(Dark Line) Anus

External Ventral:

Mouth

Clitellum Genital

Setae

Sperm Ducts Female

Genital Pores

Internal:

Intestine Gizzard

Crop

Seminal Vessicles

Seminal Recepticles

Aortic Arches

Esophagus

Ph

arynx

Ganglia

(Brain)

Internal w/o Digestive…

Nerve Cord

(Like our Spinal Cord)

Seminal Receptacles