Module 9 Evolution

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

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

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

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

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

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

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

Biogenesis: Life comes from life Disproven by: Francesco Redi

Biogenesis: Life comes from life Disproven by: Louis Pasteur

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)

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

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

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

3 Selection Mechanisms Stabilizing Directional Disruptive

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

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

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

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!

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

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

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

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

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