Population genetics Flashcards
Members of a species can ___ &
produce ___ offspring
interbreed; fertile
Species have a __ gene pool
shared
all of the alleles of all individuals in a population
gene pool
different species do not ____ by interbreeding
exchange genes
•Different species that interbreed often produce ___ offspring e.g. Mule
sterile or less viable
•A group of the same species living in an area
population
•No two individuals are exactly alike (variations)
population
•More ___ individuals survive & pass on their traits
Fit
Formation of new species
speciation
One species may split into 2 or more species
speciation
A species may evolve into a new species
speciations
•Combines Darwinian selection and Mendelian inheritance
Modern Synthesis Theory
study of genetic variation within a population
Population genetics
Population genetics emohasize on ___
quantitative characters
comprehensive theory of evolution (Modern Synthesis Theory) was ntroduced by
Fisher & Wright
Modern synthesis theory recognizes that ___ are responsible for the inheritance of characteristics
GENES
Modern synthesis theory recognizes that ___, not individuals, evolve due to ___ & ___
POPULATIONS; natural selection,genetic drift
Modern synthesis theory recognizes that ___ usually is due to the gradual accumulation of small genetic changes
SPECIATION
•The_________ describes the evolution in terms of genetic variations in a population that leads to the formation of a new species.
modern synthetic theory of evolution
Changes occur in gene pools due to mutation, natural selection, genetic drift, etc.
Microevolution
Gene pool changes cause more VARIATION in individuals in the population
microevolution
States that by itself, the process of heredity in a random mating population does not change either allelic
frequencies or genotypic frequencies at a given locus
Hardy-Weinberg Principle
•Used to describe a non-evolving population.
Hardy- Weinberg principle
Shuffling of alleles by meiosis and random fertilization have no effect on the overall gene pool.
Hardy-Weinberg Principle
____ are NOT expected to actually be in HardyWeinberg equilibrium
Natural populations
•Deviation from Hardy-Weinberg equilibrium usually results in ____
evolution
5 Assumptions of the H-W Principle
- Large population size
- No migration
- No net mutations
- Random mating
- No natural selection
H-W principle:
The gene pool of a ____ population remains ___ over multiple generations (_____ doesn’t change)
NON-EVOLVING; CONSTANT; allele frequency
Causes of Microevolution (5)
• Genetic Drift
• Natural Selection
• Gene Flow
• Mutation
• Non-random mating
the change in the gene pool of a small population due to chance
• Genetic Drift
success in reproduction based on heritable traits results in selected alleles being passed to relatively more offspring (Darwinian inheritance)
• Natural Selection
Cause ADAPTATION of Populations
• Natural Selection
-is genetic exchange due to the migration of fertile individuals or gametes between populations
• Gene Flow
- a change in an organism’s DNA
• Mutation
- Mates are chosen on the basis of the best traits
• Non-random mating
Factors that Cause Genetic Drift (2)
•Bottleneck Effect
• Founder Effect
- a drastic reduction in population (volcanoes, earthquakes, landslides …)
- Reduced genetic variation
- Smaller population may not be able to adapt to new selection pressures
•Bottleneck Effect
- occurs when a new colony is started by a few members of the original population
- Reduced genetic variation
- May lead to speciation
Founder Effect
Modes of Natural Selection (3)
• Directional Selection
• Disruptive selection
• Stabilizing Selection
- Favors individuals at one end of the phenotypic range
• Directional Selection
- Most common during times of environmental change or when moving to new habitats
• Directional Selection
- Favors extreme over intermediate phenotypes
• Disruptive selection
- Occurs when environmental change favors an extreme phenotype
Disruptive selection
- Favors intermediate over extreme phenotypes
• Stabilizing Selection
- Reduces variation and maintains the current average
• Stabilizing Selection
•Variation in a species due to climate or another geographical condition
Geographic Variations
•Populations live in different locations
Geographic Variations
Other Sources of Variation (3)
• Mutations
• Genetic Recombination
• Co-evolution
- source of most genetic differences between individuals in a population
• Genetic Recombination
-Often occurs between parasite & host and flowers & their pollinators
• Co-evolution
