1. Invertebrate Evolution

2. From Protist to Animials & Fungi

3. Opisthokonta = common ancestor of Animals and
Choanoflagellates and fungi
Choanoflagellates – most closely related to animals

4. How it Happened
Some relative of Choanofalgellate(Protist?) mutated to become multicellular instead of colonial
Colonial cells live together but can survive if separated from the colony
Cells of multicellular organisms CAN NOT live on their own
All Animals are multicellular,
Heterotrophs that
reproduce with egg & sperm

5. Proterospongia = Protist & common ancestor to all animals?

6. Proterospongia: Colonial, Unicellular Protists

7. Sponge choanocytes (collar cells)

9. Phylum Porifera Sponges 3 types of cells No tissues
Collar cells (choanocytes)
Amoebocytes
Epidermis cells (protective outer layer of cells)
No tissues
Cells held together by ‘jelly’
Skeleton of spicules & spongin protein

11. Intracelluar digestion
Collar cells take in food by endocytosis
Food digested in food vacuoles
Some food passed to amoebocytes
Amoebocytes carry food around sponge body. (circulaton)

12. Other Porifera Traits Asymmetrical = no symmetry
Respiration by diffusion
Excretion by diffusion
Reproduction = male gametes released into water, filtered out of water by another sponge.
Female gametes stay inside until fertilized.
Zygote grows into a swimming larva.
Larva settles to ground & becomes sessile adult

13. Eumetazoa = Animals with True Tissues

14. Phylum Cnidaria Have stinging cells = cnidocytes Have tentacles
Have myocytes =
muscle like cells that contract
1st predatory animals
Have Radial symmetry = sit and wait predator
1st nervous system =
nerve net & eye spots

16. Digestion & Circulation
Have gastrovascular cavity for digestion & circulation
1st extra cellular digestion – cells lining GVC secrete digestive enzymes into GVC to digest food
Evolutionary advantage = can eat larger food
Cillia lining GVC push digested food particles around the body
GVC branches into all tentacles: comes near all cells

18. Respiration & Excretion
Respiration by diffusion
Excretion by diffusion
Both are possible since entire body is only a few cell layers away from external water

19. Reproduction = complex life cycle
Medusa = swimming
Polyp = sessile
Medusa =sexual
Egg & sperm
External fertilizaion
Polyp = asexual
Budding