Evolution natural selection and phenotypes
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Evolution: Natural Selection and Phenotypes. Big Idea 1: Process of evolution drives the diversity of life. Essential Knowledge. 1A1: Natural selection is a major mechanism of evolution. 1A2: Natural selection acts on phenotypic variations.

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Evolution natural selection and phenotypes

Evolution: Natural Selection and Phenotypes

Big Idea 1: Process of evolution drives the diversity of life


Essential knowledge
Essential Knowledge

  • 1A1: Natural selection is a major mechanism of evolution.

  • 1A2: Natural selection acts on phenotypic variations.

  • 1A3: Evolutionary change is also driven by random processes


Evolution
Evolution

  • Change in genetic makeup of a population over time.

  • Natural selection is its major driving mechanism.



Darwin said
Darwin said…

  • Competition for limited resources results in differential survival.

What’s wrong with this picture though???


Natural selection
Natural Selection

  • Individs w/ more favorable phentoypes (physical features) are more likely to survive and produce more offspring, passing down traits to subsequent generations!



Genetic Code: DNA/RNA

Physical features and Behaviors


Types of natural selection
Types of Natural Selection

1) Stabilizing Selection: Selective pressures select against the 2 extremes of a trait.

  • Ex: Better to be average!


Types of Natural Selection

2) Directional selection: 1extreme of the trait experiences selection against it.

  • Ex: giraffes w/ short necks


Types of Natural Selection

3) Disruptive selection: Selection pressures act against individuals in middle of 2 extremes of the trait.

  • Ex: Don’t be average


Evolutionary fitness
Evolutionary Fitness

  • To be fit, you must be able to reproduce!

  • Measured by reproductive success.



Genetic variation is good for you
Genetic Variation is Good For You!

  • A diverse gene pool is important for survival of a species in a changing environment.


Adaptation

  • A genetic variation that is favored by selection and provides an advantage to an org. in a environment.

  • Occurs naturally through environmental pressures.




Natural selection acts on phenotype
Natural Selection Acts on Phenotype Genetic Drift?

  • Environments may change and act as a selective mechanism on populations.


Peppered moth video clip
Peppered Moth Video Clip Genetic Drift?


If the environment changes different genetic variations can be selected in each generation
If the environment changes, different genetic variations can be selected in each generation.

Global warming and earlier flowering time


Phenotypic variations occur b/c of random changes be selected in each generation(mutations) and new gene combinations (fertilization and meiosis)


Some p henotypic variations i ncrease f itness
Some be selected in each generationPhenotypic Variations Increase Fitness

  • Ex: Sickle cell anemia (Ss) makes you far less likely to die from malaria. Heterozygote advantage.


Whose fitness will be decreased
Whose fitness will be decreased? be selected in each generation


Humans impact variation
Humans Impact Variation be selected in each generation

  • Often times decreasing it…food crops have been artificially selected to be genetically similar.


Wooly worm lab
Wooly Worm Lab be selected in each generation

  • Natural Selection and Chi Square Test!


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