Mechanisms of evolution

• There is a fit between organisms and their environments, though not always a perfect fit.
• Evolution results from selection acting upon genetic variation within a population.
• New heritable traits can result from recombinations of existing genes or from genetic mutations in reproductive cells.
• Mutations are random, but selection is not; selection is dependent on many factors.
• Traits that are advantageous often persist in a population.
• The process by which advantageous traits are maintained and disadvantageous traits are weeded out of a population is known as natural selection.
• Inherited characteristics affect the likelihood of an organism's survival and reproduction.
• Depending on environmental conditions, inherited characteristics may be advantageous, neutral, or detrimental.
• Random factors affect the survival of individuals and of populations.
• Natural selection acts on individuals and populations in a nonrandom way.
• Evolution acts on what exists.
• Organisms cannot purposely produce adaptive mutations in response to environmental influences.
• Populations evolve.
• The proportion of individuals with advantageous characteristics may increase due to their increased likelihood of surviving and reproducing.
• Evolution may occur as a result of genetic drift.

• Genetic Variation
• Natural Selection