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EVOLUTIONARY PROCESSES AND PATTERNS • Theory of Special Creation – Species unchanged through time & independent of one another EVOLUTIONARY PROCESSES AND PATTERNS • Theory of Spontaneous Generation – New organisms (species) suddenly appear EVOLUTIONARY PROCESSES AND PATTERNS • Prior to Darwin and Wallace Lamarck EVOLUTIONARY PROCESSES AND PATTERNS • Theories of Evolution • Darwin and Wallace – Species are related to one another, and they change over time, thus species existing today have descended, with modifications, from other preexisting species Evolution • What is evolution? • Microevolution: • Macroevolution: Population Characteristics • Species – A group of organisms capable of interbreeding Population Characteristics • Species – A group of organisms capable of interbreeding and producing fertile offspring. – Isolated gene pools • Isolation – – – – Temporal Spatial Mechanical Behavioral Genes go in but they don’t Come out! Evolution • Allopatric Speciation Evolution • Sympatric Speciation ? Evolution • Parapatric Speciation ? Darwinian Selection • All natural selection results in evolution, but not all evolution is the product of natural selection. • What is evolution? • What is natural selection? • What is an adaptation? Darwinian Selection • All natural selection results in evolution, but not all evolution is the product of natural selection. • What is evolution? Darwinian Selection • All natural selection results in evolution, but not all evolution is the product of natural selection. • What is evolution? – Evolution is the change in allele frequencies (or traits) over time. • What is natural selection? • What is an adaptation? Darwinian Selection • All natural selection results in evolution, but not all evolution is the product of natural selection. • What is evolution? – Evolution is the change in allele frequencies (or traits) over time. • What is natural selection? – Natural selection is the differential reproductive success resulting from an adaptation. • What is an adaptation? Seeds Ticks off of iguanas etc. Tools use to get insects Leaves and fruit Insects, spiders, nectar Darwinian Selection Is there variation about a trait? Darwinian Selection Is there an excess of individuals so that only some animals live to reproduce? Are resources limited? Darwinian Selection - Drought of 1977 eliminated seed set by most of the plants producing small soft seeds. - Large and hard seeds became dominant food item. - Only large birds with deep beaks could defend resources and access the resources Darwinian Selection Did evolution occur? - 1983 El Niño produced 1359 mm of rain and lavish seed set by the small soft seeded plants. - Birds with shallow beaks harvest these seeds more efficiently and thus reproduced better than birds with deep beaks, undoing the selection shown here. - Fluctuating environmental conditions maintained both phenotypes. Types of Selection • Directional Selection • Stabilizing Selection • Disruptive selection Directional Selection • Phenotype at one extreme of population distribution has selective advantage. • Leave more offspring Types of Selection • Directional Selection • Stabilizing Selection • Disruptive selection Stabilizing Selection • Intermediate phenotypes have selective advantage. Types of Selection • Directional Selection • Stabilizing Selection • Disruptive selection Disruptive Selection • Intermediate phenotypes selected against Darwinian Selection • The consequences of natural selection are expressed at the population level. Genetic drift • Genetic drift results in a gradual loss of genetic diversity • Over time an individual locus and gene frequency will drift until one allele becomes fixed Convergent Evolution ISOLATION AND CONVERGENT EVOLUTION Convergence – Myrmecophages anteaters, aardvark, aardwolf, numbat, pangolins ISOLATION AND CONVERGENT EVOLUTION Convergence – Cursorial herbivores pronghorn, capybara, guanaco, kangaroos digestive tract, dentition, elongated limbs Convergent Evolution • Batesian Mimcry – Benign species resembles a noxious or dangerous species Convergent Evolution • Mullerian Mimicry – Noxious species resemble each other Convergent Evolution • Mullerian Mimicry – Noxious species resemble each other – Pitohui birds in New Guinea Convergent Evolution • Aggressive Mimicry – Noxious or dangerous species resembles a benign one Coevolution Association Parasitism Effect on Species A Positive Effect on Species B Negative Commensalism Positive None Mutualism Positive Positive Predation Positive Negative Competition Negative Negative
