What is a gene pool?
The sume total fo all the genes in a population at any given time
What is allele frequency?
The relative frequency of an allele within a population
What are the features of allele frequency?
- Not linked to whether it codes for a dominant or recessive characteristic
- Not fixed
What is the equation for allele frequency, and what do the symbols represent?
p + q = 1
p = dominant allele, q = recessive allele
What does the Hardy-Weinberg principle do?
Models the relationship between the frequencies of alleles in a population that is stable and not evolving
What are the assumptions for the Hardy-Weinberg principle to work?
- Genes don’t mutate
- There is no migration
- Population is large
- No mating between generations
- No selection pressures
What is the equation for the Hardy-Weinberg Principle, and what do the symbols represent?
p^2 + 2pq + q^2 = 1
p^2 = frequency of homozygous dominant genotype
q^2 = frequency of homozygous recessive genotype
2pq = frequency of heterozygous genotype
What factors affect evolution?
- Mutations
- Sexual selection
- Gene flow
- Genetic drift
- Natural selection
What is genetic drift?
Change in allele frequency due to the random nature of mutations/chance events
What is gene flow?
The movement of alleles between populations
Why are small populations more likely to become extinct?
Because they have limited genetic diversity and cannot adapt to change as easily as a large, highly diverse population
What is the founder effect?
When few individuals colonise a new area, and their offspring experience an initial loss in genetic variation. Extreme genetic drift
What is a genetic bottleneck?
When large numbers of a population die prior to reproducing leading to reduced genetic biodiversity within the population, and reduced gene pool
What is a genetic bottleneck caused by?
Catastrophic events, e.g natural disasters
What are limiting factors?
Factors with limit or decrease the size of a population
What are the two types of limiting factors?
Density-dependent and density-independent factor
What are exampeles of density-dependent factors?
Competition, predation, parasitism, communicable disease
What are examples of density-independent factors?
Climate change, natural disasters, seasonal change, human activities
What is the positive aspect of genetic bottlenecks?
A beneficial mutation will have a much greater impact, and lead to the quicker development of a new species
What are the 3 types of selection?
Stabilising, directional and disruptive selection
Define stabilising selection
Natural selection that favours average phenotypes
Define directional selection
Natural selection that favours one extreme phenotype
Define disruptive selection
Natural selection that favours both extremes of a phenotype
What is the typical shape for distribution of variation of a phenotype?
Bell-shaped curve, normal distribution
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19.1 Mutations And Variation26
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19.2 Control Of Gene Expression23
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19.3 Body Plans17
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20.1 Variation And Inheritance25
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20.2 Monogenic Inheritance18
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20.3 Dihybrid Inheritance5
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20.4 Phenotypic Ratios20
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20.5 Evolution28
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21.1 DNA Profiling15
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21.2 DNA Sequencing And Analysis3
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21.3 Using DNA Sequencing15
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21.4 Genetic Engineering20
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21.5 Gene Technology And Ethics20
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22.1 Natural Cloning In Plants6
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22.2 Artificial Cloning In Plants7
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22.3 Cloning In Animals13
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22.4 Microorganisms And Biotechnology3
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22.5 Microorganisms, Medicines And Bioremediation10
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22.6 Culturing Microorganisms In The Laboratory22
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22.7 Culturing Microorganisms On An Industrial Level6
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22.8 Using Immobilised Enzymes11
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23.1 Ecosystems12
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23.2 Biomass Transfer Through An Ecosystem27
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23.3 Recycling Within Ecosystems30
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23.4 Succession25
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23.5 Measuring The Distribution & Abundance Of Organisms13
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24.1 Population Size16
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24.2 Competition11
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24.3 Predator-Prey Relationships7
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24.4 Conservation And Preservation9
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24.5 Sustainability14
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24.6-9 Environmentally Sensitive Ecosystems16
