1. Time Line of Animal Evolution
1st Fossil evidence of animals 570 mya = Proterozoic Eon
Adaptive radiation in early Cambrian Period of the Phanerozoic Eon
Cambrian Explosion due to
increased oxygen in atmosphere
more energy
predators become more mobile

2. Evolution of Animals
Some type of Protist mutated to become multicellular
Multicellular organisms start as a single cell (zygote) and grow into organisms with groups of specialized cells performing different functions
All animals are multicellular

3. multicellular

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

5. Proterospongia: Colonial, Unicellular Protists

6. Sponge collar cells

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

9. 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)

10. Other Porifera Traits Asymmetrical = no symmetry
Respiration by diffusion
Excretion by diffusion

11. All other Animals have True Tissues
Multi cellular

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

13. Nerve net

15. Cnidocytes

16. Digestion & Circulation
Have gastrovascular cavity for
digestion & circulation
1st extra cellular digestion
– cells lining GVC secrete digestive enzymes
Evolutionary advantage = can eat larger food
Cillia push digested food around the GVC
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 water

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