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PHYLUM PORIFERA

Sponges are

- simplest invertebrate animal

- more than 5,000 species

- mostly marine, some fresh

Their bodies contain pores - thus the name “Porifera”.

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They are multicellular but organized at the cellular level only - without tissues or organs.

Beating flagella pump water through the pores bringing food and oxygen. Sponges can pump volumes of water up to 20,000 times their own volume.

This cleans the oceans as the sponges feed on bacteria and plankton.

Reproduction may be sexual or asexual.

Asexual is by external buds or internal gemmules. Sexual is by broadcasting gametes into the water.

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Three kinds of sponges have supporting structures called spicules composed of:

1. calcium carbonate spines

2. silica spines

3. elastic fibers called spongin - only this type is used for commercial sponges

The meroplanktonic larvae settle into sessile adults.

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PHYLUM CNIDARIA

ex: (jellyfish, anemones, corals)

- two tissue layers - an outer epidermis and inner gastroderm

- nerve net with stinging capsules called nematocysts

- radial symmetry with 2 body types:

1. polyp

2. medusa

Portuguese man-of-wara colonial Cnidarian

Sea Anemone

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The Man-of-War has a gas filled float and individuals that function like specialized organs. Some are carnivores with digestion in food vacuoles.

The coral animal may live as a free-floating polyp or build colonies into reefs, but not all corals build reefs.

1. stony coral - hermatypic or reef builders. The polyp grows in 6 parts to form a body of calcium carbonate

ex: brain, staghorn, golf ball

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2. soft coral - polyps with 8 tentacles

While part of the reef, they do not build reefs because their bodies are a soft keratin.

ex. sea fans, gorgonians

3. hydrocoral - false corals resemble the anemone and contain powerful neumatocysts that cause skin irritation

ex: fire coral

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CORAL BLEACHING

• Coral bleaching, occurs when heat drives out algae living within coral tissues

• indicator of stress that could eventually kill coral populations

• Upper temperature limits 30-35 C

• If temperature returns to normal quickly, coral recovers, otherwise coral dies