1. Invertebrates I: Jellyfish and Worms
Chapter 15

2. An invertebrate is an animal without a backbone.
Still has a skeleton

3. The Jellyfish: A Cnidarian
Phylum that contains many animals that have tentacles with stinging cells!
The Jellyfish: A Cnidarian
Hydrostatic skeleton
Support system like a balloon filled with water
The two layers of tissue found in jellyfish are called the ectoderm and endoderm

4. Endoderm and Ectoderm
Layers are one cell thick
Inside the endoderm is the gastrovascular cavity which is where the jellyfish digests his food
The mouth is the only opening
No brain

5. Nematocysts Jellyfish Activities
Nematocysts shoot out a tube that penetrates skin, scales etc. and forces out poison that paralyzes or kills small animals. Digestive enzymes from the endoderm break down the food in the gastrovascular cavity.
Jellyfish Activities
Nematocysts

6. Jellyfish “Swim” Jellyfish don’t use their tentacles to swim
A set of muscle fibers around the rim of the mouth contract which forces water out of the gastrovascular cavity thus propelling the jellyfish in jerky movements
Play Video

7. The Planarian: A Flatworm
Bilateral Symmetry = 2 equal sides
Free-living flatworm that lives in freshwater streams and soil

8. Nerves
Neurons are long thin nerve cells found throughout the body of an animal or human
A collection of neurons wrapped in protective coverings is called a nerve

9. Planarian’s Nervous System
Ganglion (simple brain)
Stimulus- is something an organism can sense.
Planarians sense touch and respond to light

10. Planarian’s Digestive System

11. Roundworms
Phylum Nematoda

12. Ascaris (common roundworm)
Release eggs into intestinesexit through feceseggs eaten by grazing animaleggs hatchlarvae burrow through intestines to the bloodstream and make their way to the lungs then the throatreswallowedlarvae grows to adulthood

13. Segmented Worms
Phylum Annelida

14. Earthworm Body
Earthworms have an epidermis which exchanges gases with the environment
Must be moist
Outer coating, called cuticle, protects the earthworm
Must be thin

15. Earthworm Movement Uses two sets of muscles for support and movement
Circular
Length

16. Earthworm’s Nervous System
All over the earthworm there are tiny sensory receptors.
sense a stimulus and start an impulse that travels the neuron
Chemicals, light, temp etc.
There are two large ganglia in the 3rd segment
There is one small ganglion in each segment connected together to form the nerve cord.

17. Earthworm’s Digestive System
Follow the soil through the worm’s body!!!
Upper lip pulls in moistened food
Passes pharynx
Glands secrete liquids to lube
Esophagus funnels food to the crop
Crop is a swelling the stores food
Food goes to the gizzard
Gizzard is a bulge- mechanical digestion
They eat soil which contain leaves, fungi, and small creatures.
Ground up food passes into the intestine
Digestive enzymes break down the food into soluble substances
Indigestible parts pass through the anus
Please Establish Clean Gobbling In Digestion Ahead

19. Earthworm’s Circulatory System
Closed Circulatory System- the blood in a worm never leaves the continuous network of blood vessels.

20. Earthworm’s Circulatory System
Follow the blood through the earthworm’s body!!!
Blood is in the main dorsal blood vessel (acts as the heart)
It is pushed forward to the five aortic arches (control blood pressure)
Down the ventral blood vessel on the underside of the worm
Smaller and smaller arteries to capillaries where exchange happens
Moves through veins back to the dorsal blood vessel (heart)
Earthworm’s Circulatory System
Daily Artificial Venting After Cleaning Vigorously

22. Earthworm’s Respiratory System
The earthworm breathes through it’s moist skin! The oxygen seeps through the skin into the capillaries and carbon dioxide seeps out of the capillaries into the air.
In emergencies, earthworms can go for hours without oxygen

23. The Earthworm’s Excretory System
All but the first and last segments have looped excretory vessels that channel waste out of the skin through small pores.