Evolution Primers

• Isn't Evolution Just a Theory???

• How Does Evolution Really Work?

• How Do We Know Evolution Happens?

Limits on Adaptation through Natural Selection

• A population’s ability to adapt to new A population’s ability to adapt to new environmental conditions through environmental conditions through natural selection is natural selection is limited by its limited by its gene poolgene pool and and how fast it can how fast it can reproducereproduce..– Humans have a relatively slow Humans have a relatively slow

generation time (decades) and output generation time (decades) and output (# of young) versus some other species.(# of young) versus some other species.

Common Myths about Evolution through Natural Selection

• Evolution through natural selection is Evolution through natural selection is about the most descendants.about the most descendants.

• Misconception 1: survival of the fittest Misconception 1: survival of the fittest does not mean survival of the strongest – does not mean survival of the strongest – it is referring to it is referring to REPRODUCTIVE SUCCESSREPRODUCTIVE SUCCESS

• Misconception 2: Evolution involves some Misconception 2: Evolution involves some grand plan of nature in which species grand plan of nature in which species become progressively more perfectbecome progressively more perfect– Organisms do not develop certain traits Organisms do not develop certain traits

because they need them.because they need them.– There is no such thing as genetic perfection.There is no such thing as genetic perfection.

Evolution and Adaptation

• Co-EvolutionCo-Evolution– Populations of two Populations of two differentdifferent species species interactinginteracting over a long period of time over a long period of time

– Changes in the gene pool of one Changes in the gene pool of one species can lead to changes the gene species can lead to changes the gene pool of another speciespool of another species

• Predator-Prey Relationships (salamander Predator-Prey Relationships (salamander and snake – the coffee pot incident)and snake – the coffee pot incident)

• Plant defense mechanisms (mistletoe plant)Plant defense mechanisms (mistletoe plant)

Ecological Niches and AdaptationEcological Niches and Adaptation

• Ecological nicheEcological niche– Total way of life or functional role Total way of life or functional role

of a species in an ecosystem.of a species in an ecosystem.

• HabitatHabitat– Physical location of a speciesPhysical location of a species

Occupation

Address

Ecological Niches and AdaptationEcological Niches and Adaptation• Fundamental nicheFundamental niche

– Full potential range of the physical, Full potential range of the physical, chemical, and biological factors a chemical, and biological factors a species can use if there were species can use if there were nono directdirect competitioncompetition from other species. from other species.

• Realized nicheRealized niche– Part of a species fundamental niche Part of a species fundamental niche

that are actually used.that are actually used.

Broad and Narrow Niches

• Generalist speciesGeneralist species– Species with a Species with a broadbroad ecological niche. ecological niche.

• Live in many different places.Live in many different places.• Eat a variety of food.Eat a variety of food.• Tolerate a wide range of environmental Tolerate a wide range of environmental

conditions.conditions.(flies, mice, deer, catfish, humans)(flies, mice, deer, catfish, humans)

• Specialist speciesSpecialist species– Species with a Species with a narrownarrow ecological niche. ecological niche.

• Live only in one type of habitatLive only in one type of habitat• Use only a few types of foodUse only a few types of food• Tolerate only a narrow range of climatic and Tolerate only a narrow range of climatic and

other environmental conditions.other environmental conditions.(tiger salamander, red-cockaded woodpecker, (tiger salamander, red-cockaded woodpecker, spotted owls, pandas)spotted owls, pandas)