Variation and Evolution
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What are the types of variation?
• Continuous • Discontinuous • Heritable • Non heritable
Define Variation
Variation is the differences between individuals of the same species.
What is an organisms phenotype?
The total appearance of the organism
What is discontinuous variation?
Variation that shows a limited number of phenotypes allowing them to be categories. -Normally controlled by one gene (monogenic) -Bar graphs, Pie Charts -Not effected by environment
What is continuous variation?
Variation that cannot be categories due to the number of phenotypes. -Normally controlled by many genes (polygenic) -Normal distribution curve -Effected by the environment
Define Heritable Variation
Refers to the difference in phenotype due to genetics.
Define Non-heritable Variation
Refers to the differences in phentype due to the environment.
Define Interspecific Competition
Competition for resources between members of different species.
Define Intraspecific Competition
Competition for resources between members of the same species.
Define Biotic Factors
The living factor of an ecosystem
Name four biotic factors affecting population size
• Predation • Parasitism • Disease • Competition
Define Abiotic Factors
The non-living factor of an ecosystem
Define Gene Pool
All of the different alleles in the individuals that make up a population.
What is the difference between contest competition and scramble competition?
Contest competition has a clear winner who gains all the resource whereas in scramble competition the resource is split to many individuals.
What is evolution?
The change in allele frequencies in the gene pool of a population over time due to natural selection.
How does natural selection cause a change in allele frequency in a population?
The frequency of unfavourable/disadvantageous alleles decrease.
Define Selection Pressure
The effect of the selective agencies acting on the population, driving evolution by natural selection.
What are selective agencies?
Environmental factors that can alter the frequency of alleles in a population such food supply, climate, breeding site and human impact.
What is genetic drift?
The change in the frequency of an allele by chance in small populations.
What is the founder effect?
When a small founder population with a limited gene pool become isolated from the larger parental population. Allele frequencies are no longer reflective of the original population
What is the Hardy-Weinberg principle?
The Hardy-Weinberg principle states that the frequency of alleles and genotypes within a population will remain constant from one generation to the next requiring certain conditions. It allows us to estimate the frequencies of dominant and recessive alleles within a population.
What conditions are required for the Hardy-Weinberg principle to be fulfilled?
• Large population • No mutations • No migration/isolated population • No selection • Random mating
What is the Hardy-Weinberg equation for genotype frequency?
p² + 2pq + q² = 1 p² = frequency of AA (homozygous dominant) 2pq = frequency of Aa (heterozygous) q² = frequency of aa (homozygous recessive)
What is the Hardy-Weinberg equation for allele frequency?
p + q=1 p = frequency of the dominant allele (A) q = frequency of the recessive allele (a)