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Unformatted text preview: Beak of the Finch essays-adaptation-natural variation-theme of studies-Natural selection-Darwinism and its ideas • Two major points o Evolution “ descent with modification ” explains both the unity and diversity of life All organisms are related by an ancestor Represented by a branching tree o Crucial mechanism of the evolutionary process, adaptation by natural selection 5 observations • 1. Populations have the capacity to grow in size (exponential growth) • 2. Populations tend to be stable in size (logistic growth and carrying capacity) • 3. Resources are limited • 4. Individuals in a population vary extensively in their traits (different colored ladybugs) • 5. Relatives resemble each other- some variation is heritable. 3 inferences • 1. More individuals are produced than the environment can support which leads to a “struggle for existence” and only few offspring survive. • 2. Survival and reproduction are NOT RANDOM, variation of traits effects fitness. • 3. Unequal ability of individuals to survive and reproduce leads to changes in a population with, favorable characteristics becoming more common over generations. 1 conclusion • population adapt to their environment because individuals vary, variation influences survival and reproduction, and the variation is heritable. • The best variants will be selected for, and their traits will become more common, shifting the average trait in the population toward a better form. -adaptations • Shifting the average traits in the population toward a better form-mechanism • Nature selects directly on individuals phenotype • Natural selection acts on individuals: (not evolution) o Some individuals have traits that are selected for o Others have traits that are selected against • Natural selection leads to evolution only when it chooses among heritable traits • Evolution occurs at the scale of the population-definition of fitness • fitness depends, in part, on inherited traits • variation of traits affects fitness-morphological convergence...
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