Evolution vs. Natural Selection

• Evolution is CHANGE = Change in allele frequency

• Natural Selection = nature is choosing organisms that are more likely to survive & reproduce MORE

  • Variation is required

    • Sexual reproduction

    • Mutation

    • Horizontal gene transfer (bacteria)

Genetic Drift

• Random changes in allele frequency (by chance)

• Needs a small population

• Founder effect

  • BY CHANCE, a tiny subset of a large population gets cut out then finds a new population (natural disaster)

  • BIG change in allele frequency

• Bottleneck effect

  • A tiny subset of a large populations survives while the rest die (natural disaster)

  • Change in allele frequency

  • Think about how a bottle slowly pours (lets say) tiny paper stars out, the massive amount of paper stars that stay in the bottle represent the organisms that died

• Gene Flow

  • When a gene flows from one population to another

  • Change in allele frequency (no way!)

Hardy-Weinberg Equilibrium

• Allele frequency (how frequent a trait is)

• P = The number of a certain allele / total number of alleles in the entire population

  • P=200+100/600

  • Finding the dominant trait → HH has 100×2, Hh has 100, and 100 hh has 0

    • 100 HH

    • 100 Hh

    • 100 hh

• P² + 2pq + q² = 1

  • Big numbers

  • No mutation

  • No natural selection

  • No gene flow

  • No random mating

Phylogeny

• Macroevolution - long periods of time

• Common ancestors

• Speciation

  • Species = Members can interbreed and have viable offspring

  • Horse + donkey = sterile mule

• Allopatric

  • Geographically split apart and speciate

    • New food sources

    • Adaptations

    • Ex: Island vs. mainland

• Sympatric

  • Still in the same location, but speciate

  • Different habitats, food source, etc.

  • Polyploid

    • Error in meiosis, extra chromosomes

• Reproductive isolation

  • Stop reproducing

  • Non-viable offspring

  • Prezygotic

    • Habitat (different locations)

    • Temporal (mate at different times)

    • Mechanical (physically cannot)

    • Gametic (won’t fuse)

    • Behavior (courtship)

  • Postzygotic

    • Reduced hybrid viability (cannot live past a certain age, dies off)

    • Reduced hybrid fertility (sterile)

    • Hybrid breakdown (dies out eventually)

Common Ancestry

• Structures:

  • Homologous features = same ancestry, different function

  • Vestigial structures = have due to common ancestry, but we don’t use it (tailbone)

  • Analogous structures = different ancestry, similar function

• Evidence:

  • Molecular biology = less differences, closer relatedness (less time to diverge)

  • Biogeography

  • Fossils

• Phylogenetic trees

  

• Mass extinction

  • Permian Triassic (before dinosaurs)

  • Cretaceous Tertiary (dinosaurs died, debris, no sunlight by a meteoroid)

  • Right now

Origin of Earth

~4.5 billion years ago, Earth was found

~3.9 billion years, oceans form

~3.5 billion years ago, life formed (stromatolite fossils)

• RNA world hypothesis (first life form)

• Building blocks (monomers) created polymers, and so on…

Miller-Urey Experiment

• Inorganic to organic

  • Organic could come from inorganic to produce life (not accurate to Earth’s initial atmosphere, but debatable and possible)