Evolution of populations Flashcards
What is population genetics?
The study of how populations change genetically over time
What is micro evolution?
A change in allele frequencies in a population over generations
What is a population
A localized group of individuals capable of interbreeding and producing fertile offspring
how do you count alleles?
Assume 2 alleles
frequency of dominant alleles (B)=p
frequency of recessive alleles (b)= q
frequency of all alleles must equal 100% p+q=1
How do you count individuals?
Frequency of homozygous dominant pXp=p2 Frequency of homozygous recessive q X q= q2 frequncy of heterozygotes 2pq frequency of all alleles must equal 100% p2+2pq+q2=1
how can you determine if a population is evolving?
If the predicted and observed frequencies are not a match, then the population is evolving
What are the five conditions of non-evolving populations?
No mutations Random Mating No natural selection Extremely large pop size No gene flow ( no alleles coming or going)
What are five major factors that can alter allele frequencies and bring evolutionary change?
Mutations Natural Selection Genetic drift Gene flow Non Random mating
What are mutations?
Changes in the nucleotide sequence of DNA that can cause new genes and alleles to arise
What is a point mutation?
A change in one base in a gene
insertion: addition of single base pair
deletion: removal of single base pair
What are the different modes of point mutation
Silent: mutation in non coding region (harmless)
Nonsense: mutation in a gene coding region, does not allow protein to be produced
Missense: either conservative or non conservative
What are the three modes of natural selection?
Directional selection, Disruptive selection
stabalizing selection
What is directional selection?
Favours individuals at one end of the phenotypic range
ex. peppered moths, antibiotic resistance, giraffe neck size
What is disruptive selection?
favours individuals at both extremes of the phenotypic range (rarest mode)
ex. Black bellied seed crackers (african bird)
What is stabilizing selection?
favours intermediate variants and acts against extreme phenotypes
ex. human birth weight, medium height plants, Siberian husky, clutch size in birds
What is Genetic drift?
Allele frequencies fluctuate unpredictably from one generation to the next
tends to reduce genetic variation ( loss of alleles)
significant in small populations
What is gene flow?
Non-random movement of genes into or out of a population by migration
members of one population may breed with occasional immigrants from an adjacent population of the same species
-introduces new genes or alters existing gene frequencies
What effects can gene flow have?
Reduce differences between populations over time
Decrease the fitness of a population
Can increase the fitness of a population
What is fitness?
Measure of reproductive success
how many offspring an individual contributes to the next generation
What is sexual selection?
Non random mating- individuals are choosy in their selection of mates
What is intrasexual selection?
Competition among individuals of one sex (often males) for mates of the opposite sex
Intersexual selection
Mate choice by individuals of one sex (usually females) are are choosy in selecting their mates
