Ch. 33 Pt 1- Intro to invertebrates

Evidence for sponges being the most basal lineage

Lack true tissues, simple body plan is similar to ancestor of all animals, molecular dna shows, similar to choanocytes

Structure and feeding of porifera

Structure- Porous body with no symmetry. Composed of two cell layers with jelly-like mesohyl in between.

Feeding- Filter feeders—> water moves through ostia, moves into the spongocoel, and exits through osculum. Inside, choanocytes use flagellum to draw in water and trap food particles. Amoebocytes digest food and distribute nutrients

Draw cross-section of sponge

Osculum into spongocoel→choanocytes collect food particles→ spicules in mesohyl→amoebocytes take in nutrients and transport them→water leaves through ostium

Phylum cnidaria- traits shared in eumetazoa. Who is not in this clade?

True tissues- ectoderm and endoderm. Sponges are not in this clade

Characteristics shared in cnidaria

Radial symmetry, diploblastic (ectoderm and endoderm with mesoglea in between), gastrovascular cavity (opening for mouth and anus), specialized stinging cells called cnidocytes, two body forms (polyp, medusa- frees swimming)

Draw structure of cnidarian

Polyp- mouth/anus on top, medusa-mouth/anus on bottom. Gastrovascular cavity, endoderm, mesoglea, endoderm.

Cnidocyte

Specialized stinging cells found on tentacles

Nematocyst

Capsule within cnidocyte containing coiled, harpoon-like threat. When triggered, it rapidly injects pray, injecting toxins to immobilize it.

Generalized life cycle of cnidarian

Polyp stage- sessile (asexual reproduction-budding)

Medusa stage- free swimming (sexual reproduction- gametes)—> Fertilization—> Zygote—> Planula larva—> Settles into new polyp

Hydrozoa

Obelia, hydra

Scyphozoa

True jellyfish

Cubozoa

Box jellies

Anthozoa

Sea anemones, coral (antho- antler)

Draw life cycle of obelia

Medusa-> Meiosis-> Egg and sperm (haploid-2n)-> Fertilization-> developing blastula-> Planula(larva)-> developing polyp-> mature polyp-> polyp with feeding and reproductive polyps-> Medusa

Draw life cycle of typical jellyfish

Adult medusa→ Meiosis→Egg and sperm (haploid- 2n)→ Fertilization→ Planula (larva)→ Mitosis→ Scyphistoma→ Budding polyp→ Ephyra (juvenile medusa)