19-processes Of Evolution Flashcards
Evolution
Change in the genetic makeup of a population over time.
European mindset in 18th century: (regarding species)
- species are unchanging
- uniquely designed for their environment
- earth only 6,000 yrs old
- strong religious (Christian) influence
Jean Baptist Lamarck (Lamarck’s Folly, 1809)
- use and disuse
- inheritance of acquired characteristics
-refuted By Weismann in 1890 (mouse tails)
Charles Darwin
- made observations in South America that organisms changed over time
- Galapagos islands
Adaptations
Inherited characteristics of organisms that enhance survival and reproduction in a given environment
Natural Selection
Individuals with certain inherited traits tend to survive and reproduce better, due to these traits
Origin of species
- Darwin and Wallaces publishing on evolutionary theory
- diversity of life
- unity of life
- match between organisms ad their environment - Used artificial selection as compelling evidence
- Common ancestor
!!!!
- population =smallest unit that can evolve
- evolution requires genetic variation in the gene pool of a population
- Mendel’s work in genetics strengthened Darwin’s argument
- “tree of life” (phylogenies trees, cladistics)
- change in allele frequency over time
Genetic Variation
Differences among individuals in the composition of their genes
Sources of Genetic variation
- Mutation*
- Gene-duplication
- Sexual reproduction
Mutation
- Random change in DNA nucleotide sequence
- Driving force for all other variation
gene-duplication
-Chromosomal sections may be copied twice during replication
(4 possible outcomes) (notes)
sexual reproduction
- independent assortment
- crossing over
- Random fertilization
Micro evolution
Evolutionary change at the smallest level (population)
- mutation
- Natural Selection
- Genetic drift
- gene flow
- sexual selection
Natural selection
- *mutation is still the driving force
- those with beneficial traits produce more offspring
- traits become more common
Genetic drift
- Random events that cause allele frequencies to fluctuate unpredictably
- founder events
- bottlenecks
Gene flow
- movement of fertile individuals (or their gametes) into or out of a population
- immigration (in)
- emigration (exit)
Sexual selection
- individuals with certain characteristics are more likely to obtain mates
- Intrasexual selection (competition between same sex individuals)
- Intersexual selection (mating choice)
- Drawbacks…
- best trait for mating is not always good for survival
Hardy-Weinberg Equilibrium
- p + q = 1
- p^2 + 2pq + q^2 = 1
- p = frequency of dominant allele
- q = frequency of recessive allele
- p^2 = DD
- q^2 = dd
- 2pq = Dd
Conditions for H.W Equilibrium
- no mutation
- no natural selection
- infinite population
- no gene flow
- random mating
- very rare
Types of Natural selection
Directional selection -favors 1 extreme Stabilizing selection -favors intermediate Disruptive selection -favors both extremes
Limitations of Natural Selection
- selection can only act on existing conditions
- limited by historical constraint
- adaptations have drawbacks
- things change at random in nature
