Ch. 8 Evolution Flashcards
Microevolution
a generation to generation change in the frequencies of alleles within a population
Allele
alternative forms of the same gene
Gene pool
all the alleles, in all individuals, that make up a population
Sources of Variation: Mutations
→ change in DNA sequence that may have no effects, harm or help fitness
Sources of Variation: Sexual reproduction
→ meiosis scrambles existing alleles
Non random mechanisms of microevolution (3 types of selective pressures)
Natural selection
Directional
→ individuals at one end on the phenotype range have higher fitness
Stabilizing
→ individuals near the center of the phenotype range have a higher fitness (ie. lots of babies)
Disruptive
→ individuals at the upper and lower ends of the [phenotypic range have higher fitness;
may lead to 2 distinct phenotypes
\
Pesticide Resistance
→ first time spraying kills 99%, but subsequential sprayings are less effective
→ directional selection (towards resistant pests)
Antibiotic resistance
→ directional selection
Sexual selection
→ individuals with certain inherited traits are more likely to obtain mates than others
Artificial selection
→ humans intentionally breeding plants/animals to produce certain traits (not random)
Random mechanics of microevolution: Genetic Drift
→ change in gene pool due to chance
→ impacts smaller populations
Bottleneck effect
→ population size is reduced therefore gene pool is reduced
→ by chance some alleles will be more frequent than others
→ decreases genetic variation in population (ie. natural disasters)
The founder effect
→ The loss of genetic variation when a new population is established by a very small number of individuals from a larger population
→ The smaller the colony, the less genetic variability
Gene flow
→ involves the random exchanges of genes with another population
→ reduces genetic differences between populations
What is a species
→ biological species concept
