1. Module 9
Evolution

2. Abiogenesis
Life first arose from non-living material in a “primordial soup”
Experimentally tested by Miller and Urey
Also called SPONTANEOUS GENERATION
H2S
CO2 N2 CO
CH4
Amino acids

3. Heterotroph Hypothesis
Explains evolution of prokaryotic cells
Earliest cells had to take in nutrients (heterotrophic)
Earliest cells had to live in oxygen free conditions (anerobic) O2

4. Heterotroph Hypothesis
Photosynthetic prokaryotic cells evolved, allowing for release of free oxygen
Led to ozone layer O2 O2 O2

5. Heterotroph Hypothesis
Oxygen led to evolution of aerobic cells O2 O2 O2

6. Endosymbiont Hypothesis
Explains the evolution of eukaryotic cells
A symbiotic relationship formed between larger and smaller prokaryotic cells – smaller cells became mitochondria and chloroplasts
YouTube - The Evolution of Eukaryotic Organisms: Endosymbiotic Theory

7. Multicellular Life
Multicellular organisms are made of eukaryotic cells
The evolution of eukaryotic cells allowed multicellular life to evolve, and eventually colonize land

8. Biogenesis: Life comes from life
Although life may have arisen spontaneously, life continues through other life!
Spontaneous generation has been disproven by scientists

9. Biogenesis: Life comes from life
Disproven by: Francesco Redi

10. Biogenesis: Life comes from life
Disproven by: Louis Pasteur

11. Evolution = CHANGE over time
Occurs through the process of NATURAL SELECTION
Nature “selects” the best adapted organisms to survive and reproduce
Natural Selection Stated Clearly
(10 min)

12. What is an Adaptation? A “heritable” trait
Makes an organism better suited to its role in the ecosystem
May be structural, behavioral, or physiological
Structural:
defensive structures, camouflage, mimicry
Behavioral:
Herding, schooling, growling
Physiological:
enzymes, oxygen transport, sight

13. Theory of Natural Selection
Proposed by Charles Darwin
4 “Requirements”
Natural Selection
Nature “selects” the best adapted
Survival of the “fittest”
Best adapted individuals have greater reproductive success
Variation
Different phenotypes in the population
Overproduction
Leads to competition

14. Individuals DON’T EVOLVE!
Individuals don’t evolve – populations do! This requires a change in the “gene pool”
MUTATION:
The raw material for change
Can be selected FOR
Can be selected AGAINST

15. 3 Selection Mechanisms
Stabilizing
Directional
Disruptive

16. Reproductive Isolation
Speciation
Speciation:
The development of a new species
Geographic Isolation
Natural
Selection
Reproductive Isolation

17. Timeframe for Evolution
GRADUALISM:
Occurs over a long period of time with the accumulation of small changes
PUNCTUATED EQUILIBRIUM:
Occurs with speciation in rapid bursts with 1000’s of years of stability between changes
Gradualism
Punctuated Equilibrium

18. Evidence for Evolution
Fossil Record
May give exact age or relative age

19. Evidence for Evolution
Biochemical Evidence
Comparing amino acid sequences
REMEMBER…
If amino acids are similar, DNA is similar because DNA is a code for making proteins!

20. Evidence for Evolution
Homologous Structures
Similar bone arrangement, but different functions
REMEMBER…
Analogous structures do not give evidence of evolution from a common ancestor!

21. Evidence for Evolution
Vestigial Structures
Not functional, but may have been important in an ancestor
Vestigial Structures - SciShow

22. Evidence for Evolution
Comparative Embryology
Similar embryos give evidence of a common ancestor

23. Evolution Today
Evolution is still happening! However, it’s usually too slow to observe… EXCEPT: 1) Pesticide Resistance

24. Evolution Today Evolution is still happening!
However, it’s usually too slow to observe…
EXCEPT:
Antibiotic
Resistance