Module 9 Evolution Abiogenesis Life first arose from

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 H 2 S CO 2 N 2 CO CH 4 cids no a i m A

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) O 2

Heterotroph Hypothesis • Photosynthetic prokaryotic cells evolved, allowing for release of free oxygen • Led to ozone layer O 2 O 2

Heterotroph Hypothesis • Oxygen led to evolution of aerobic cells O 2 O 2

Endosymbiont Hypothesis • Explains the evolution of eukaryotic cells • A symbiotic relationship formed between larger and smaller prokaryotic cells – smaller cells became mitochondria and chloroplasts • You. Tube - 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

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” Variation Different phenotypes in the population Overproduction Leads to competition Natural Selection Nature “selects” the best adapted Survival of the “fittest” Best adapted individuals have greater reproductive success

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

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

Timeframe for Evolution Gradualism 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 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!