2. Kingdom Animalia eukaryotic, multicellular, heterotrophic
feed by ingestion

3. Animal Evolution

4. Non-molting vs. Molting
Embryonic Mouth Formation
Body Symmetry
Organs vs. non-organs or
Tissues vs. non-tissues

6. Kingdom Animalia Most animals have: Sense organs Nervous system
Muscles
Digestive tract
Sex organs

7. Brief History of the World
Hadean Eon—4.63.8 BYA
-Earth & Moon formed as solid bodies
2) Archean Eon—3.82.6 BYA
-Origin of Life
-Origin of Prokaryotes
-Fermentation
-Photosynthesis

8. Brief History of the World
3) Proterozoic Eon—2.60.57 BYA
-Continental Drift begins
-O2 Revolution
-Krebs Cycle
-Origin of Eukaryotes
-Ediacaran Period—first multicellular animals
-Cryogenian period –snowball earth 720—635 MYA

9. Precambrian (Ediacaran) Fossils 635-541 MYA
All soft bodied—poor fossil record

10. Brief History of the World
4) Phanerozoic Eon—0.54Today
Cambrian Explosion
-First skeletal remains
-Origin of most major multicellular phyla

11. THE CAMBRIAN EXPLOSION (490-543 MYA)
~ 35 animal phyla originated in
~ 50 million yrs

12. Early Cambrian Fossils

13. New Cambrian fossil – Nature Feb.24, 2011

14. Two Major Questions Why and when did multicellularity arise?
What caused the Cambrian Explosion?

15. Multicellularity (>700 MYA)
Advantages of
Large size
Cell specialization (Division of labor)

16. Humans
Birds
Dinosaurs
Amphibians
Fish
Cephalopods
Echinoderms
Arthropods
Jellyfish
Science Nov. 6, 2015
Sponges

17. Multicellularity (>700 MYA)
Multicellularity originated
When unicellular organisms stayed together after cell division
Originated many times

18. What Caused the Cambrian Explosion?

19. What Caused the Cambrian Explosion?
1)There was a real “explosion.”
(i.e. In a few million years
all major phyla evolved from protozoans)
Why?

20. What Caused the Cambrian Explosion?
Major forms were already
present. They were small
and without skeletons. Did not fossilize well.
Then at the Cambrian they increased in size and developed skeletons.
--DNA evidence supports this view

21. What Caused the Cambrian Explosion?
What could have prompted increase in animal diversity, increased size and skeletal development?
Three explanations:
Environmental
Developmental
Ecological

22. What Caused the Cambrian Explosion?
Environment:
1) Sea chemistry change. Shift towards high calcium carbonate and high pH would encourage
biomineralization calcium based skeletons.
Nature 6/4/2017
2) Oxygen revolution
(Large size and active metabolism requires large amounts of oxygen to generate large amounts of ATP via the mitochondria.)

23. Oxygen Revolution

24. What Caused the Cambrian Explosion?
Development: Genetic modifications might have caused major change in development into embryo thus to adults.
Horizontal gene transfer of genes coding for biomineralization occurred from bacteria to sponges occurred allowed skeletal development.

25. What Caused the Cambrian Explosion?
Ecological: Arms race between predator and prey led to diversity of attack (e.g. “teeth” and rapid swimming ) and defense strategies like burrowing and exoskeletons = co-evolution

26. Let’s Look at the Burgess Shale Great Cambrian Fossils

27. The Burgess Shale Great Cambrian Fossils
Anomalocaris