Natural Selection Pt 2 -Genetic changes can result from gene recombination during gamete formation and from mutations -These events are responsible for variety and diversity within each species -Natural selection favors the organisms that are better suited to survive in a given environment -Those not well suited to the environment may die before they can pass on their traits to the next generation

Natural Selection Pt 2 -Species struggle to find food or to escape being consumed themselves -As the environment changes, selection for adaptive (or helpful) traits can also change -Traits that were once adaptive/helpful may become disadvantageous because of change -Adaptations: -occupy a niche -finding shelter/ camouflage -gathering food -reproduction

Natural Selection Pt 2 Industrial Melanism -A classic example of natural selection is the peppered moth in Manchester, England -Light-colored moths used to flourish in the region and dark-colored moths were rare -However, once the industrial revolution started, light-colored moths became scarce and dark-colored moths became more prevalent

Natural Selection Pt 2 -Two explanations have been developed – one is that the dark moths were hidden from predators due to soot covering the entire city; another explanation is that light moths were susceptible to the chemical emissions put out by the factories -In any case, the light moth had an adaptive advantage until the environment changed which lead to the dark moth having an adaptive advantage in the end as their population grew and light moths declined

Testing the Explanation Think of an experiment where you would be able to test whether or not it was actually the pollution that killed off the light moths and not the dark moths or whether it might have been something else like predators. Consider your control, independent variable, and dependent variables.

Ideas About Evolution There were two ideas about how evolution occurred through natural selection: one based on changing in response to need and one based on some organisms surviving and some not. Which one is best supported by the mechanism of natural selection?