Biology 2483A Lecture Notes - Lecture 6: Adaptation, Disruptive Selection, Gene Flow

• School: Western University
• Department: Biology
• Course: Biology 2483A
• Professor: Hugh Henry

Document Summary

Case study #1 (trophy hunting & inadvertent evolution): Trophy hunting removes the largest and strongest males the ones that would sire many healthy offspring. In one population, 10% of males were removed by hunting each year, the average size of males and their horns decreased over 30 years of study. Among other species, african elephants are poached for ivory; the proportion of the population that have tusks is decreasing. Rock shrimp are all born male, and become females when they are large enough to carry eggs. Commercial harvesting takes the largest individuals, which are all females. Genes for switching sex at a smaller size became more common, resulting in more females, but smaller females lay fewer eggs. Evolution can be viewed as genetic change over time or as a process of descent with modification. Biological evolution is change in organisms over time. Evolution can be defined more broadly as descent with modification.