The Simplest Animals

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The Simplest Animals

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The Simplest Animals. Phylum Porifera. Invertebrates Animals without tissues (Sponges) All are aquatic and sessile (stay in one place) The body plan is asymmetrical Made of a loose arrangement of cells with no defined cell layer. Sponges!. Sponges. - PowerPoint PPT Presentation

Transcript of The Simplest Animals

Page 1: The Simplest Animals

The Simplest Animals

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Phylum Porifera Invertebrates Animals without tissues (Sponges) All are aquatic and sessile (stay in

one place) The body plan is asymmetrical Made of a loose arrangement of cells

with no defined cell layer

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Sponges Have two germ layers, ectoderm and

endoderm They do have some specialized cells

• Collar cells line the inside of the body cavity and have flagella that move water and food into the sponge through pores

• Water exits via the osculum (the open end of the sponge

• Digestion occurs in collar cells, or special cells called amoebocytes

• Amoeobocytes wander around in a gelatinous mixture called mesenchyme

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Sponge Reproduction Sponges are hermaphrodites (produce

both male and female gametes) They only produce one gamete at a time

(they can’t fertilize themselves) Fertilized eggs turn into free-swimming

larva The larva undergoes metamorphosis and

develops into a full grown sponge They can also reproduce asexually, by

budding or branching

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Role of Sponges Important food

source for snails, sea stars and fish

Provide shelter for smaller invertebrates inside their body cavity

Some clean up the ocean floor by releasing chemicals

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Phylum Cnidaria Include Hyrda, Jellyfish, Sea Anemones,

and Corals Aquatic, have tentacles and possess true

tissues Radially symmetrical Have endoderm and ectoderm, separated

by jelly-like mesoglea Have nerve, muscle and digestive tissues Nerve nets encircle the body, so if

touched, they can flatten out and pull tentacles inward

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Cnidarians!

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Cnidarian Body Structure Either polyp or

medusa form

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Cnidarian Feeding Capture food using

stinging cells containing nematocysts (stinging capsules)

Captured food is digested in the gastrovascular cavity (gut) which has only one opening

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Cnidarian Reproduction Hydra may reproduce asexually by

budding Hydra and all medusae reproduce

sexually by releasing eggs or sperm into the surrounding water

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Role of Cnidarian Food for fish, turtles and small

animals Sea anemones and coral reefs form

protective structures Coral reefs protect land along coastal

areas from rough water