Division Ave. High School Ms. FogliaAP Biology
AP Biology 2007-2008
Evolutionby
Natural Selection
AP Biology
AP Biology
Life has changed & changed the Earth
Living creatures havechanged Earth’s environment,
making other life possible
AP Biology
In historical context Darwin did not originate the idea of evolution Geologic theories of Earth’s age & history cleared the
path for evolutionary biologists
…immeasurable time…
AP Biology
(5)(5) Over long periods of time, and given a steady input of Over long periods of time, and given a steady input ofnew variation into a population, these processes lead tonew variation into a population, these processes lead tothe the emergence of new speciesemergence of new species
Essence of Darwin’s ideas(1)(1) VariationVariation exists in natural populations exists in natural populations
(2)(2) Many Many more offspringmore offspring are born each season are born each seasonthan can possibly survive to maturitythan can possibly survive to maturity
(3)(3) As a result, there is a As a result, there is a struggle for existencestruggle for existence - - competitioncompetition
(4)(4) Characteristics beneficialCharacteristics beneficial in the struggle in the strugglefor existence will tend to become morefor existence will tend to become morecommon in the population, changing thecommon in the population, changing theaverage characteristics of the populationaverage characteristics of the population - - adaptationsadaptations
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Effects of Selection Driving changes in a population
Division Ave. High School Ms. FogliaAP Biology
AP Biology
Natural Selection Selection acts on any trait that affects
survival or reproduction predation selection physiological selection sexual selection
AP Biology
Predation Selection Acting on predator & prey
behaviors & habits camouflage (mimicry) speed defenses (physical & chemical)
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Physiological Selection Acting on body functions
fitness (food-gathering) physiology efficiency (oxygen, food, water) disease resistance protection from injury biochemical versatility
HOT STUFF!Some fish had the
variation of producinganti-freeze proteins
5.5 mya5.5 myaThe Antarctic OceanThe Antarctic Oceanfreezes overfreezes over
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Sexual Selection Acting on reproductive success
attractiveness to potential mate fertility of gametes successful rearing of offspring
Survival doesn’t matterif you don’t reproduce!
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Sexual selection
It’s FEMALE CHOICE, baby!
AP Biology
The lion’s mane…
Females are attracted tomales with larger, darkmanes
Correlation with highertestosterone levels better nutrition & health more muscle & aggression better sperm count / fertility longer life
But imposes a cost to male HOT! Worth it??
Division Ave. High School Ms. FogliaAP Biology
AP Biology
Sexual selection Sexual selection acts in all
sexually reproducingspecies the traits that get you mates it influences morphology &
behavior it acts on both
males and females
Jacanas