Chapter 23 Flashcards
1
Q
Population
A
- Groups of individuals inbreeding and producing fertile offspring.
- Populations evolve, individuals don’t
2
Q
Genetic Variation
A
- Evolution acts on heritable traits that vary between organisms (genetic variation)
- Mendel discovered that genes are the basis for heritability
- Alternative versions of genes (alleles) account for variation in inherited characters:
- organisms inherit 2 copies of each gene (1 per parent)
- if alleles differ, dominant determines appearance and recessive has no noticeable effect
- alleles separate during gamete formation, and end up in different gametes (Law of Segregation)
3
Q
Sources of Genetic Variation
A
- Sexual reproduction = recombination = novel genotypes (Law of Independent Assortment)
- No change in allele frequencies, but novel combinations can be acted upon by natural selection.
4
Q
Mutations
A
Variations in Alleles:
- rare
- mostly in somatic cells (not passed on to next generation)
- While variation within a population is essential for evolution to occur, it does not guarantee that a population will evolve.
5
Q
Allele Frequencies
A
- Every allele has a frequency (proportion) in the population
- Number of alleles = individuals x2 (diploid)
- The frequency of alleles adds up to 1: p = dom and q = rec.
- see review lecture for calculations*
6
Q
Hardy-Weinberg Principle
A
- Hardy-Weinberg equation calculates the expected frequency of genotypes from allele frequency
- Frequencies of alleles and genotypes in a population remain constant from generation to generation
- H-W may be used to test whether or not evolution is occurring at a specific locus in a population
- Describes a population that is not evolving. If the theory does not hold then the population is not evolving.
- p^2 = 2qp + q^2 = 1
- p^2: frequency of homo dominant
- 2pq: frequency of hetero
- q^2: frequency of homo recessive
- SEE REVIEW LECTURE*
7
Q
Hardy-Wienberg Equilibrium
A
-When a population is not in H-W equilibrium the observed outcome does not match the expected
8
Q
5 Conditions for Non-Evolving Populations Rarely Met in Nature
A
- No mutations
- Random mating
- Large population size
- No gene flow
- No natural selection
9
Q
3 Evolution Factors
A
- Natural Selection
- Genetic Drift
- Gene Flow
10
Q
Natural Selection
A
- Acts on phenotype
- Adaptive evolution
- 3 Forms of Selection:
- Directional
- Disruptive
- Stabilizing
11
Q
Directional Selection
A
Extreme phenotype favoured
12
Q
Destructive Selection
A
Phenotypes extremes favoured
13
Q
Stabilizing Selection
A
Intermediate phenotypes favoured
14
Q
Genetic Drift
A
- Chance changes in allele frequencies
- reduces genetic variation through loss of alleles
- important in small populations
15
Q
What do small populations result from?
A
- The Founder Effect
2. The Bottleneck Effect
