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Questo esame si sostiene in inglese: le lezioni e le domande sono in inglese. L'interfaccia resta in italiano.
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Part 1 of 1
Evolution is the change in the genetic composition and heritable characteristics of biological populations over successive generations. Charles Darwin formulated the core scientific mechanism of adaptive evolution: natural selection.
Darwin's theory of evolution by natural selection rests on four verifiable biological observations: 1. Heritable Variation: Individuals within any natural population exhibit phenotypic variations that arise through genetic mutations and sexual recombination. 2. Overproduction of Offspring: Organisms produce more offspring than their environment's finite resources can support, resulting in a struggle for survival. 3. Differential Reproductive Success: Individuals possessing heritable traits best suited to local environmental conditions are more likely to survive, reproduce, and pass their advantageous alleles to offspring. Differential reproductive success is the central driving engine of natural selection. 4. Gradual Adaptation: Over generations, advantageous alleles increase in frequency within the population gene pool, leading to adaptive evolutionary change.
Natural selection contrasts sharply with Lamarck's earlier hypothesis of the inheritance of acquired characteristics, which incorrectly asserted that traits acquired during an organism's lifetime (such as stretched muscles) could be directly transmitted to offspring.
Worked example
Step 1: Analyze how industrial melanism in the peppered moth (Biston betularia) exemplifies natural selection. Step 2: Initial state: In unpolluted forests, light-colored moths were camouflaged against lichen-covered tree trunks, whereas dark (melanic) mutants were easily spotted and predated by birds. Step 3: Environmental change: Industrial soot darkened tree trunks and killed lichens. Dark moths gained a camouflage advantage, while light moths suffered intense predation. Step 4: Outcome: Dark moths achieved higher survival and differential reproductive success, causing the frequency of the melanic allele to rise dramatically over generations.
For the exam
1.Differential reproductive success is the central concept in Darwin's theory of evolution by natural selection.
2.Natural selection operates by transmitting traits acquired during an individual's adult lifetime to offspring.
3.Genetic mutations and sexual recombination generate the raw heritable variation needed for natural selection.
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