Variations

There can be manyThere can be manydifferent variationsdifferent variationsFor a trait.For a trait.

Variations of a trait can increase Variations of a trait can increase or decrease an organisms chance or decrease an organisms chance of survival in an environmentof survival in an environment

Variations

Stabilizing Selection Stabilizing Selection is natural selection is natural selection that favors average that favors average individuals in a individuals in a population.population.

Variations

Consider a population of Consider a population of spiders in which an average spiders in which an average size is survival advantage. size is survival advantage.

Predators might see and Predators might see and capture spiders that are capture spiders that are larger than average, and larger than average, and smaller spiders might find it smaller spiders might find it hard to find foodhard to find food

Variations

Directional Selection Directional Selection occurs when natural occurs when natural selection favors one selection favors one of the extreme of the extreme variations of a trait.variations of a trait.

Variations

For example a population For example a population of of woodpeckers pecking holes woodpeckers pecking holes in in trees to eat insects living trees to eat insects living under the bark.under the bark.

Suppose the insects live Suppose the insects live deep in the wood of the deep in the wood of the tree. Only woodpeckers with tree. Only woodpeckers with long beaks could feed on that long beaks could feed on that insect.insect.

Variations

Disruptive selection Disruptive selection occurs when either occurs when either extreme of a trait is extreme of a trait is selected.selected.

Variations

Consider a population of marine Consider a population of marine organisms called “Limpets.” organisms called “Limpets.”

The sell color of limpets ranges The sell color of limpets ranges from white to tan to dark brown. from white to tan to dark brown.

On light-colored rocks white On light-colored rocks white shelled limpets have an advantageshelled limpets have an advantage

On Dark colored rocks, dark-On Dark colored rocks, dark-colored limpets have an advantagecolored limpets have an advantage

Variations• Species that were

once similar to an ancestral species becomes increasingly different

• Adaptive Radiation-Change to fit diverse habitats….

Wat UP Cousins!!!

Variations• Two “Distant”-ly related organisms

develop the same traits…Flying Squirrel

Flying Phalanger

Do I know You?

Are we related?