Origins of Life and Darwin’s Theory of Evolution

How did life begin? Miller & Urey’s Experiment - produced amino acids by passing hydrogen, methane, ammonia, and water through electric sparks. - demonstrates how simple compounds could form organic compounds.

Miller & Urey’s Experiment

(*endosymbiotic theory*) Progression of Life 1. Anaerobic prokaryotes (no oxygen) 2. Photosynthetic bacteria (produce oxygen) 3. Aerobic prokaryotes 4. Prokaryotes join together to form eukaryotes* (*endosymbiotic theory*) 5. Protists, plants, fungi, & animals - occurred due to sexual reproduction

- Idea that eukaryotes formed from groups of prokaryotes Endosymbiotic Theory - Idea that eukaryotes formed from groups of prokaryotes

Charles Darwin Charles Darwin(1809-1882) - the father of evolution - believed environment determined traits Darwin traveled around the world for 5 years on the HMS Beagle collecting data on many unique organisms.

Darwin’s Journey

Giant Tortoises of the Galápagos Islands Pinta Tower Marchena Pinta Island Intermediate shell James Fernandina Santa Cruz Isabela Santa Fe Hood Island Saddle-backed shell Floreana Hood Isabela Island Dome-shaped shell

Evidence for Evolution 1) Fossil Record Shows species that once existed. Comparing fossils and rock layers one can find relationships showing change.

Evidence: Fossils

Evidence: 2) Geographic Distribution Different continents have different species. Species may evolve similar traits if environments are the similar.

Geographic Distribution Beaver Beaver Muskrat Beaver and Muskrat Coypu Capybara Coypu and Capybara NORTH AMERICA Muskrat Are these the same two animals? SOUTH AMERICA Capybara Coypu

Evidence 3) Homologous structures Structures in different species that share similar design/function. Shows species have common ancestors.

Homologous Body Structures Turtle Alligator Bird Mammal Ancient lobe-finned fish

Homologous Structures

Cladogram Shows evolutionary relationships

Evidence: 4) Vestigial structure structure with no function in present-day organisms, but was useful to an ancestor. Natural selection does not get rid of the organ.

Evidence: Embryology 5) Embryology- comparing early growth stages of organisms. Fish chicken rabbit human

Embryology

6) Biochemical Evidence - Comparing DNA of organisms - shows how closely organisms are related - can link organisms to common ancestors

A Summary of Darwin’s Theory 1. Differences are inherited. 2. Organisms produce more offspring than can survive. 3. Increase in organisms causes competition. 4. Best adapted organisms survive & reproduce. 5. Today’s species are descended with modifications from their ancestors.

Genetics and Evolution Gene pool = all the alleles in a population. Ex- Pea plants: - Height alleles: T = tall t = short Relative frequency = % of each allele - Height alleles: T = 70% t = 30% Evolution = change in relative frequency.

Relative Frequencies of Alleles Section 16-1  Relative Frequencies of Alleles Sample Population Frequency of Alleles allele for brown fur allele for black fur 48% heterozygous black 16% homozygous black 36% homozygous brown

Sources of Evolution 1. Mutations 2. Genetic variation due to sexual reproduction 3. Environmental changes

Phenotypes for Single-Gene Trait 100 80 60 40 20 Frequency of Phenotype (%) Widow’s peak No widow’s peak Phenotype

Single trait mutation Observe this population of delicious spiny puffs in pond water. Imagine there’s a predator that loves to eat delicious blue spiny puffs instead of green spiny puffs. What would happen to the color of spiny puffs over time?

Year # 1

Year # 2

Year #3

Bell Curve for Polygenic Trait Phenotypes Frequency (%) of Phenotype Phenotype (height) 5 ft 5 ft 8 in 6 ft 6 in

Natural Selection of Polygenic traits Changes create 3 types of selection 1. Directional selection 2. Stabilizing selection 3. Disruptive selection

Directional Selection One trait is favored. Shifts the population’s average toward that trait. Key Low mortality, high fitness High mortality, low fitness Food becomes scarce.

Stabilizing Selection Average traits are favored. Stabilizing Selection Selection against both extremes keep curve narrow and in same place. Key Low mortality, high fitness High mortality, low fitness Percentage of Population Birth Weight

Disruptive Selection Only organisms with extreme traits survive. Creates two different extreme phenotypes. Largest and smallest seeds become more common. Key Beak Size Beak Size Low mortality, high fitness Population splits into two subgroups specializing in different seeds. Number of Birds in Population High mortality, low fitness Number of Birds in Population

Genetic Drift (Founder’s Effect) Sample of Original Population

Genetic Drift (Founder’s Effect) Sample of Original Population Founding Population A Founding Population B

Genetic Drift(Founder’s Effect) Sample of Original Population Descendants Founding Population A Founding Population B

Speciation Evolution of new species - Large allele changes can create new species - Isolation can cause allele changes: Types 1. Behavioral Isolation 2. Geographic Isolation

Behavioral Isolation A change of behavior within a population that creates 2 new gene pools. Example : Birds with different mating songs.

Geographic Isolation If a geographic barrier splits a population, then two new genetic pools may form.