Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Natural Selection and Speciation Stabilizing Selection • favors the average individual • reduces variation in a population Examples • birth weight in humans • Siberian husky- muscle mass • “living fossils”- organisms that have remained unchanged for millions of years (sharks, crocs) Birth Weight Directional Selection • favors one of the extreme variations • leads to rapid evolution of a population Examples PEPPERED MOTHS PESTICIDE/ANTIBIOTIC RESISTANCE Disruptive Selection • favors both extreme variations Examples • Darwin’s finches –small beaked birds could eat small seeds –large beaked birds could eat large seeds –medium beaked birds could not eat either seed efficiently STABILIZING DIRECTIONAL DISRUPTIVE Divergent Evolution • occurs when closely related species evolve to look differently • populations change to adapt to different environments • adaptive radiation- one species evolves into several different species Darwin’s Finches Hawaiian Island Honeycreepers Convergent Evolution • occurs when species of different ancestry evolve to look alike –occurs b/c species occupy similar environments • analogous traits Examples • whales and fish • birds and butterflies • marsupial and placental mammals Speciation • evolutionary formation of a new species