16 B SPONGES AND CNIDARIANS How are sponges

16 B- SPONGES AND CNIDARIANS How are sponges and cnidarians animals?

Classifying Animals ■ Largest category- invertebrates – In every phylum except chordate! ■ Divided due to number of germ layers – Sponges- 0 – Cnidarian- 2 – Worms- 2 or 3 – Mollusks & Echinoderms- 3

16. 6 - CLASSIFYING SPONGES

Classifying Sponges ■ Phylum Porifera – Invertebrates – No germ layers!!! ■ No digestive system ■ No nervous system ■ No circulatory system – Sessile – Asymmetrical

16. 7 - STRUCTURE AND REPRODUCTION IN SPONGES

Sponge Structure ■ Basically tubes – 1 open end ■ Supported by spicules – Spikey, stiff, needlelike things ■ Collar Cells – Have flagella – Create current

Sponge Structure ■ Intracellular Digestion – Collar cell engulfs food (phagocytosis) – Digest a little – Send to other cells to finish

Sponge Reproduction ■ Asexual– Budding ■ Sexual – Hermaphroditic ■ male & female

16. 8 - CLASSIFYING CNIDARIANS

Classifying Cnidarians ■ Phylum Cnidaria – Soft – Radially symmetric – 2 germ layers – Examples: ■ Jellyfish ■ Corals ■ Sea anemone

16. 9 - STRUCTURE AND REPRODUCTION IN CNIDARIANS

Cnidarian Structure ■ LOTS of variety!! ■ Nerve net – Nervous system made of network of nerves ■ Each cell performs own respiration & excretion ■ Have stinging cells: cnidocytes – THOUSANDS on tentacles

Cnidarian Structure 2 forms: Polyp & Medusa Polyp Medusa ■ Cup shaped – Mouth & tentacles top – Sticky basal disk bottom – Like plant w/ suction cup ■ Umbrella shaped – Swim freely – Tentacles on bottom ■ Tentacles pull food into gastrovascular cavity ■ Moves by opening & closing like umbrella ■ Some only have medusa stage (jellyfish), others only polyp (coral)

Cnidarian Reproduction Sexual & Asexual Reproduction ■ Budding ■ Splitting in Half Sexual Reproduction ■ Most reproduce this way – Male releases sperm in ocean – Female releases ova – Fertilization! – Becomes larva then polyp