Invertebrates I: Jellyfish and Worms

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Invertebrates I Jellyfish and Worms

• Chapter 15

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An invertebrate is an animal without a backbone.
Still has a skeleton
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The Jellyfish A Cnidarian
Phylum that contains many animals that have
tentacles with stinging cells!

• Hydrostatic skeleton
• Support system like a balloon filled with water
• The two layers of tissue found in jellyfish are
  called the ectoderm and endoderm

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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

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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.

• Nematocysts

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Jellyfish Swim

• Jellyfish dont 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
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The Planarian A Flatworm

• Bilateral Symmetry 2 equal sides
• Free-living flatworm that lives in freshwater
  streams and soil

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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

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Planarians Nervous System

• Ganglion (simple brain)

Stimulus- is something an organism can
sense. Planarians sense touch and respond to
light
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Planarians Digestive System
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Roundworms

• Phylum Nematoda

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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

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Segmented Worms

• Phylum Annelida

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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

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Earthworm Movement

• Uses two sets of muscles for support and movement
• Circular
• Length

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Earthworms 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.

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Earthworms Digestive System
Follow the soil through the worms 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
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Earthworms Circulatory System

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

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Earthworms Circulatory System
Follow the blood through the earthworms 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)

• Daily Artificial Venting After Cleaning Vigorously

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Earthworms Respiratory System

• The earthworm breathes through its 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
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The Earthworms Excretory System

• All but the first and last segments have looped
  excretory vessels that channel waste out of the
  skin through small pores.