Invertebrates I: Jellyfish and Worms Chapter 15

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

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

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

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

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

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

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

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

Planarian’s Digestive System

Roundworms Phylum Nematoda

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

Segmented Worms Phylum Annelida

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

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

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.

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

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

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

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

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.