Evolution Natural Selection Flashcards
What is natural selection?
The slight genetic variation among individuals which has an impact on their individual survival and consequently the number of offspring it will produce.
Acts on the phenotypical aspect of the individuals within a population
What is artificial selection?
These are human-made genetic modifications.
What is a phenotype?
Physical expression of genes
ex. B=brown eyes b= blue eyes
BB and Bb=brown eyes bb=blue eyes
What is a genotype?
The genetic constitution that governs a trait (not related to physical appearance)
What is evolution?
Any change in the frequency of a genotype
What is a gene pool?
The sum of the different alleles (variation) that produce different phenotypes
What is a population?
A locally interbreeding group within a geographic population
How to calculate an allele frequency
2 x the number of copies of the said allele + the number of heterozygous copies/ 2 x total of the population
What is the genotype frequency?
individuals with the genotype/ total# of individuals in the population
What is genetic structure?
The frequencies of different alleles at each locus and the frequencies of different genotypes
What is Hardy Weinberg equilibrium?
A population in which the frequencies of alleles and genotypes do not change from generation to generation (no evolution).
What are the requirements for a population to be considered to be in Hardy-Weinberg equilibrium?
- Mating random
- Population size is very large or infinite
- There is no migration between populations
- There is no mutation
- Natural selection does not affect the alleles under consideration
If after one generation all of these requirements are met then it is considered to be in Hardy-Weinberg equilibrium
What is the Hardy-Weinberg equation?
p^2+2pq+q^2=1
What are the known evolutionary agents?
- mutation
- Gene flow
- Genetic drift
- Nonrandom mating
- Natural selection
What are mutations?
Origin of genetic variation. A mutation is any change in an organism’s DNA
What are the types of mutations?
Harmful: Disadvantage to the individual (disease, death, etc.)
Neutral: Doesn’t have any effect in the individual’s life
Advantageous: Can help survive in certain environments and take over the population, replacing the useless traits
What is gene flow?
When individuals migrate to another population and breed in their new location.
Immigrants may add new alleles or may change their frequencies if they come from a population with different allele frequencies
What is genetic drift?
Random loss of individuals and the alleles they possess
More powerful than mutation and gene flow
What is a population bottleneck?
A small number of individuals, in a population, survive
1st type of genetic drift
What is the founder effect?
A few pioneering individuals leave the original population and colonize a new region creating a new population
2nd type of genetic drift
What is non-random mating?
When individuals make either more often with individuals of the same genotype OR more often with individuals of a different genotype
Ex. :If a genotype reproduces more with the same genotype= homozygous genotype overrepresented
What is natural selection?
Adapting to an environment. Advantages may be produced.
What is fitness?
The ability of an organism to survive and pass on its genes to the next generation
What are the characters that affect natural selection?
- Stabilizing selection
- Directional selection
- Disruptive selection
What is stabilizing selection?
Preservation of the characteristics of a population by favoring average individuals (heterozygous)
What is directional selection?
Changes the characteristics of a population by favoring individuals that vary in one direction from the mean of the population
What is disruptive selection?
Changes characteristics of a population by favoring characteristics of a population in both directions from the mean of the population
