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Evolution: the change in allele frequency in a population over time
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Evolution: the change in allele frequency in a population over time
- Descent with modification
- Traits vary among individuals
- Individuals with certain traits reproduce and have more offspring
NOT forward thinking
(organisms are not adapted to future conditions)
4 criteria for natural selection:
- Gene variation: individuals vary in the trait
- Heritability: the trait is heritable
3. Fitness variation: some individuals have higher fitness & are more successful than others at surviving & reproducing
4. Not all individuals survive: the individuals that survive are NOT a random sample of the population
(a) They have traits that make it more likely that they will survive
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If there is heritable variation in a trait, then successful variants will become more common over time
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Non-Random Mating
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In nature, mating IS NOT RANDOM with respect to sexual traits
Females/males choose a mate based on that trait
Evolving Resistance
Mutation
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Some new alleles are beneficial, others aren't
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Hardy and Weinberg
- Frequency of A = p
- Frequency of a = q
- Frequency of AA genotype is pp or p^2
- Frequency of Aa or aA genotype is 2pq
- Frequency of aa genotype is qq or *q^2
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If q allele = x, what is frequency?
(Chart on Slide 27)
x = 0.1
frequency = 0.1*0.1 = 0.01 = 1%
x = 0.2
frequency = 0.2*0.2 = 0.04 = 4%
x = 0.3
frequency = 0.3*0.3 = 0.09 = 9%
x = 0.4
frequency = 0.4*0.4 = 0.16 = 16%
x = 0.5
frequency = 0.5*0.5 = 0.25 = 25%
x = 0.6
frequency = 0.6*0.6 = 0.36 = 36%
x = 0.7
frequency = 0.7*0.7 = 0.49 = 49%
x = 0.8
frequency = 0.8*0.8 = 0.64 = 64%
x = 0.9
frequency = 0.9*0.9 = 0.81 = 81%
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Adaptive Radiation
The rapid diversification of a lineage that results in many closely related species with a wide range of adaptations
3 Features of Adaptive Radiation:
- Monophyletic group
- Rapid Speciation
- Diversified Ecologically
Ecological Opportunity:
New resource is colonized by a species, and the descendants survive in a variety of habitats. Through selection, drift, and mutation, new species arise
Key Innovations:
Trait that allows descendants to live in new areas, exploit new resources & move in new ways
Examples:
- Flowers as reproductive structures
- Feathers & wings for flight
- Lungs to breathe air