Unit 4 Flashcards
Evolution
Change in gene and allele frequencies within a population or species
Genetic drift
When populations are small chance can change allele frequencies, can lead to a fixation of alleles. Change in a population resulting in chance
Bottleneck effect
When a severe event results in a drastic reduction in numbers. Very small sample alleles survives to establish a new population
Founder effect
When a few individuals from a large population leave to establish a new population, the allele frequency of the new population will not be the same as the original population
Gene flow
When organisms migrate leaving one population and joining another, they alter the gene frequency of both. Tens to reduce differences. Genetic information is shared
Key factors in a change to a gene pool
1) Small population: Chance
2) Nonrandom mating: Preferred individuals pass on some alleles in greater numbers then others
3) Genetic mutations: New alleles are created or alleles are changed
4) Migration: Removes allied from the population
5) Natural selection: Individuals within certain alleles have greater reproductive success than others increasing the relative frequency of their alleles. Can be results of diseases, climate, food, availability, predators, mating preferences
Mutations
Point: Changes in a single base pair of DNA
Small insertion and deletions: Produce non functioning harmful genes
Large scale inversions: Often neutral, a tool for biologists
Gene duplications: Unequal crossing over during meiosis results in an additional copy of one or more genes being inserted into a chromosome
Pseudogenes: Duplicated- loose their ability to transcribe
Polypoid
Mutation that results in 3 or more sets of chromosomes when diploid gametes join to form a cell containing one or more entire sets of chromosomes
Cuvier
Theory- catastrophism. Stated that local catastrophes could cause extinction, extinct forms are then replaced by different migrating species. Determined relative age of fossils
Radiometric dating
Calculation of the age through the measurement of the decay of radio isotopes (atoms with unstable nuclear nuclear arrangement that undergoes radioactive decay) in the sample
Directional selection
Environments favours individual with more extreme variables of a trait
Stabilization selection
Environment favours most common phone type
Disruptive selection
Favours individuals with opposite extreme traits
Sexual selection
Favours the selection of any trait that influences the mating success of an individual (usually male)
Cumulative selection
Evolution of a complex structure in a process
