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Natural selection
Natural selection
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Concept of natural selection is simple, but mechanism is subtile
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Deals with survival and reproduction
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Comprises the only known process that offers an explanation for the origin
of adaptations
11.1 Different forms of leaves on the aroid vine Monstera tenuis in tropical American forests
• Different forms of leaves on the vine Monstera tenuis in tropical
American forests
• Example of adaptive development in relation to environmental
parameters
11.2 Pseudocopulatory pollination
• Adaptive shapes of flowers for pseudocopulatory pollination in the
Australian orchid Chiloglottis formicifera
• Shape is combined with other traits such as odour
11.3(2) The kinetic skull of snakes
• Adaptive skeletal structure of poisonous snakes
11.3(1) The kinetic skull of snakes
• Adaptive skeletal structure of poisonous snakes
• Form complex mechanisms “redesigned” through modification of
existing skeletal structures in other reptiles
11.4 Weaver ants (Oecophylla) constructing a nest
• Level of complexity of cooperative behaviour reaches climax in social
insects
• Genetically inherited behaviour increases the reproductive success of
the queen
Process of natural selection
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Design and function
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Consistent difference in fitness among phenotypically different classes of
biological entities
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Fitness as a product of survival and reproductive success
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Individual versus genic selection
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Natural selection versus chance effects
11.5 A child’s toy that selects small balls
• Selection for small size results in selection of red balls
• By chance, natural selection can lead to selection for correlated traits
• Selection always acts for a particular phenotypic trait, but results in
selection of the genes that code for this trait
11.7 Allele frequency fluctuates due to hitchhiking in a laboratory population of Escherichia coli
• Example of hitchhiking through fluctuations in frequency of his- and
his+ alleles in E. Coli
• Illustrates selection for new advantagous mutations and selection of
neutral alleles at the linked his locus
11.9(1) A male long-tailed widowbird in flight
• Male body traits used for display are often strongly developed
• Relationships with fitness can be examined through correlative or
experimental studies
11.9(2) Effects of experimental alterations of tail length on males’ mating success
• Male body traits used for display are often strongly developed
• Relationships with fitness can be examined through correlative or
experimental studies
11.9(3) Effects of experimental alterations of tail length on males’ mating success
• Male body traits used for display are often strongly developed
• Relationships with fitness can be examined through correlative or
experimental studies
11.11(1) Effects of individual selection and group selection on population size in the flour beetle
• Study on effects of selection for different population sizes
11.11(2) Effects of individual selection and group selection on population size in the flour beetle
• Study on effects of selection for different population sizes
11.11(3) Effects of individual selection and group selection on population size in the flour beetle
• Study of effects of selection for different population sizes
• Treatment C shows characteristics of individual selection
• Treatments A and B show characteristics of group selection
• Selection can act both within and between populations
• Selfish genetic elements
11.12 The mythical self-sacrificial behavior of lemmings
• Mytical self-sacrificial behaviour of lemmings
• Altruists versus cheaters
• Lower average turn-over of populations than of individuals reduces
likelihood of strong group selection
11.13(1) Conflict between group and individual selection
• Conflict between group selection and individual selection
• Altruistic traits may evolve through group selection if the rate of
extinction of populations with selfish genotypes is very high
11.13(2) Conflict between group and individual selection
• Conflict between group selection and individual selection
• Altruistic traits may evolve through group selection if the rate of
extinction of populations with selfish genotypes is very high
11.13(2) Conflict between group and individual selection
• Because individual selection works faster than group selection, selfish
individuals rapidly increase within populations
• May spread towards neighbouring populations though gene flow
• Leads to fixation of selfish genotypes (even if causing population
extinction)
11.14(1) The evolution of altruism and selfishness by kin selection
• Evolution of altruisim and selfishness by kin selection
• Kin selection operates at the level of individual genes
• Both behavioural strategies potentially increase the inclusive fitness of
the actor
11.14(2) The evolution of altruism and selfishness by kin selection
• Evolution of altruisim and selfishness by kin selection
• Kin selection operates at the level of individual genes
• Both behavioural strategies potentially increase the inclusive fitness of
the actor
11.17 Exaptation and adaptation
• ‘Preadaptation’ versus ‘exaptation’
• Wings in alcids can be regarded as exaptations
• Wings in penguins can be regarded as adaptations
11.18 Cross section of a bird’s eye, showing the pecten
• Non-adaptive explanations: by-product of selection, correlated
selection (hitchhiking, pleiotropy), random genetic drift, ancestral
character state
• Indications for adaptation: complexity
11.19 Small surfaces shed the hot boundary layer of air more readily than large surfaces
• Non-adaptive explanations: by-product of selection, correlated
selection (hitchhiking, pleiotropy), random genetic drift, ancetsral
character state
• Indications for adaptation: design (functional, morphological,
fysiological)
11.9(3) Effects of experimental alterations of tail length on males’ mating success
• Non-adaptive explanations: by-product of selection, correlated
selection (hitchhiking, pleiotropy), random genetic drift, ancetsral
character state
• Indications for adaptation: experimental evidence
11.20 Testes versus body weight among polygamous and monogamous primate taxa
• Non-adaptive explanations: by-product of selection, correlated
selection (hitchhiking, pleiotropy), random genetic drift, ancestral
character state
• Indications for adaptation: comparative studies
• Convergent evolution as natural evolutionary experiments
• Hypothetico-deductive methods
11.21 The problem of phylogenetic correlation in employing the comparative method
• Hypothesis testing assumes statistically independent data
• Study of convergent evolution for hypothesis testing on adaptations
assumes independent convergent evolutionary events
Conclusive remarks
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Necessity of adaptation ?
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Perfection ?
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Progression ?
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Harmony and balance ?
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Morality and ethics ?