BIOL 112 Lecture 4

« previous | Monday, September 3, 2012 | next »

Evidence for Natural Selection

Natural selection in action: viruses and bacteria become resistant to treatment
Fossils: Whales and dolphins evoled from a terrestrial ancestor
- Intermediate forms of a species (progression of species evolution)
- Vestigial characteristics (hind limbs– or lack thereof) due to misuse
Homology: Shared characteristics between taxonomically-related organisms because of common ancestor that had trait
- Anatomical: Similar forelimb structure in humans, cats, whales, and bats.
- Molecular: Similar proteins and nucleotides found across phyla; all organisms use same genetic code
Analogy: Common characteristics ("analogous") due to convergent evolution (last common ancestor lacks trait)
- Different taxa independently come up with similar solutions to adapt to similar conditions
- Sugar glider (marsupial) and Flying squirrel (eutherian)
Biogeography: Distribution of species due to adaptation and geography (isolation, continental drift)
- Why are certain species found only in certain geographic areas?

Darwin didn't know about genes

The smallest unit of evolution is a population (not individual)

Mendel's laws of inheritance for diploids (See BIOL 111 Chapter 14→)

Variants of a characteristic are encoded by different alleles
- Dominant – show phenotype
- Recessive – don't show
Diploids inherit 2 alleles (1 per chromosome)
Laws of segregation: alleles segregate randomly into gametes (egg/sperm) and are randomly recombined