Directional, Disruptive, and Stabilizing Selection

My AP Biology Thoughts

My AP Biology Thoughts

Episode #10

Welcome to My AP Biology Thoughts podcast, my name is Morgan and I am your host for episode # 10 called Unit 7 Evolution: Types of Selection. Today we will be discussing Directional Selection, Disruptive Selection, and Stabilizing Selection.

Segment 1: Introduction to types of selection: directional, disruptive and stabilizing selection

• All three are subsets of natural selection (response to environmental changes)
• All three cause a change in genetic variance of a population- alleles in the gene pool
• Directional selection- SHIFT in gene pool, favors one phenotype
• Disruptive selection- INCREASE in variance, selects extreme phenotypes and disregards ‘middle ground’
• Stabilizing selection- opposite, DECREASES variation in gene pool, gets rid of extremes and takes average

Segment 2: Example of types of selection

• Directional selection is shown through peppered moths (graph of curve moves to the right on spectrum light to dark) single phenotype favored. Result of a drastic environmental change
• Disruptive selection- mice on light sand, mice in dark grass, no middle ground (graph moves from one curve to two curves, little to no middle population) drives speciation since two populations separate
• Stabilizing selection- population of mice, this time on forest floor which is medium brown, both light and dark will stand out and not be as fit (graph goes from wide curve to narrower with more in the middle and less at sides)
• Examples shown on graphs used from the website Bio.LibreTexts.Org

Segment 3: Digging Deeper : connection between types of selection and overall evolution

• Overall, all three contribute to changes in populations and shifting of traits. Leads to speciation, especially disruptive. Under the umbrella of natural selection.
• Def. of evolution- process of organisms changing, developing and diversifying over time.
• Relates to central dogma since mutations in the gene sequences are what causes any changes in phenotypes. Difference in the DNA leads to a difference in the code sent to the RNA and therefore a difference in the protein it makes

Thank you for listening to this episode of My AP Biology Thoughts. For more student-ran podcasts, make sure that you visit www.hvspn.com. Thanks for listening!

Music Credits:

• "Ice Flow" Kevin MacLeod (incompetech.com)
• Licensed under Creative Commons: By Attribution 4.0 License
• http://creativecommons.org/licenses/by/4.0/

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