Patterns of Natural Selection

Speciation

• When a group within a species separates from other members and develops its own unique characteristics.

• The process by which organisms adapt to their environment over time.

• A method of classifying organisms based on their physical traits.

• The extinction of a species due to environmental changes.

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Types of natural selection

• Directional, Stabilizing, Disruptive

• Linear, Random, Cyclical

• Adaptive, Maladaptive, Neutral

• Convergent, Divergent, Parallel

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Directional selection example

• An example of directional selection is the increase in size of the beaks of finches (birds) during droughts.

• An example of directional selection is the decrease in size of the beaks of finches (birds) during droughts.

• An example of directional selection is the increase in the number of feathers on birds during cold weather.

• An example of directional selection is the change in color of butterflies to blend in with flowers.

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Natural selection

• The process by which organisms better adapted to their environment tend to survive and produce more offspring.

• A method of breeding plants and animals for desired traits.

• The theory that all species evolve from a common ancestor.

• A random process that affects the survival of organisms.

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Disruptive selection

• Favors average traits/phenotypes in a population.

• Selects against extreme traits/phenotypes.

• Favors extreme traits/phenotypes at both ends of the spectrum, selecting against the average.

• Promotes uniformity in traits across a population.

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Effect of Stabilizing Selection

• Leads to a decrease in genetic diversity by favoring average traits.

• Increases genetic diversity by favoring extreme traits.

• Has no effect on genetic diversity.

• Leads to an increase in genetic diversity by favoring all traits equally.

Disruptive selection example

• An example of disruptive selection is the color variation in peppered moths during industrialization.

• An example of disruptive selection is the increase in size of a species due to environmental changes.

• An example of disruptive selection is the uniform color of flowers in a garden.

• An example of disruptive selection is the decrease in population size due to overhunting.

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Normal Variation

• Refers to the range of traits present before selection occurs.

• A process that eliminates all variations in a population.

• The introduction of new traits through mutation.

• The selection of traits based on environmental pressures.

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Stabilizing Selection

• This type of selection favors the average traits, reducing the presence of extreme variations.

• This type of selection favors extreme traits, increasing the presence of average variations.

• This type of selection has no effect on trait variations.

• This type of selection eliminates all variations in traits.

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Example of Disruptive Selection

• Selection for light and dark limpets, with normal variation being less favored.

• Selection for average-sized individuals in a population.

• Selection against both extremes in a population.

• Selection for individuals with the most extreme traits.

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