Different traits arise from genetic mutations, recombination, and migration, enabling adaptation to changing environments
Niche specialization
Individuals with varied adaptations can exploit different resources, reducing competition and maximizing survival
Disease resistance
Genetic diversity provides some individuals with resistance or immunity to diseases, increasing survival during outbreaks
Environmental adaptability
Diverse traits allow for adaptation to various environmental conditions, facilitating colonization and reducing the risk of population decline
Factors contributing to genetic variation
Random genetic mutations
Genetic recombination during meiosis
Migration (gene flow)
Mutations are the primary source of new alleles and genetic diversity, providing the raw material for natural selection to act upon
Directional selection
Increases the expression of an extreme version of a trait in a population
Disruptive selection
A process that splits a population into two groups; removes individuals with average traits and favors the 2 extremes
Stabilizing selection
Eliminates extreme expressions of a trait when the average expression leads to higher fitness
Mechanisms of microevolution
Mutations
Natural selection
Genetic drift
Gene flow
Sexual selection
What was believed before?
Creationism
Catastrophism (Cuvier)
Gradualism (Hutton)
Struggle for Existence (Malthus)
Uniformitarianism (Lyell)
Inheritance of Acquired Traits (Lamark)
Intelligent Design
Conditions for evolution to not occur
Population is very large
Random mating
No mutation
No natural selection
Charles Darwin
Went on a voyage to the Galapagos islands, saw differences in species on different islands, and developed the theory of natural selection
Microevolution
Evolution can occur on a small scale, affecting a single population
Macroevolution
Evolution on a large scale, affecting changes in species across populations
Natural selection
Organisms with the "best" traits (adaptations) will live longer and reproduce more than others, causing changes in the population over time by acting on traits that are heritable
Fitness
A measure of how well you can survive in your environment
Adaptation
A feature that allows an organism to survive in its environment. Beneficial traits (adaptations) will become more common over time because organisms should live longer and thus be able to reproduce more.
Gene pool
The combined alleles of all individuals in a given population
Genetic drift
Random change in the frequency of alleles in a population over time
Gene flow
Movement of genes into and out of a population, occurring during migration and resulting in an increase in genetic variation
Sexual selection
The selection of traits that aren't necessarily good for survival fitness, but without them, you can't pass on your genes at all because you can't reproduce
Genetic equilibrium
When there are no changes in the allele frequencies in a population over time