Evolution terms & Pictures

Lamarkism  If an organism changes during life in order to adapt to its environment, those changes are passed on to its offspring Lamark said that change is made by what the organisms want or need

Natural Selection on Polygenic Traits Stabilizing selection: phenotypes in the middle range confer greater survival/reproduction, while phenotypes at both extremes lead to decreased fitness Directional selection: phenotypes at one end of the spectrum lead to greater survival/reproduction Disruptive selection: phenotypes at both ends of the spectrum lead to greater survival/reproduction, while phenotypes in the mid range are a disadvantage (least common of the three types )

Peppered Moth Evidence of Natural selection The evolution of the peppered moth is an evolutionary instance of directional selection in the moth population as a consequence of air pollution during the industrial revolution. The frequency of dark- colored moths increased at that time. Later, when pollution was reduced, the light-colored form again predominated. Industrial melanism in the peppered moth was an early experimental test of Charles Darwin’s natural selection in action

Genetic drift In each generation, some individuals may, just by chance, leave behind a few more descendants (and genes) than other individuals. The genes of the next generation will be the genes of the "lucky" individuals, not necessarily the healthier individuals

Genetic drift – bottleneck effect Occurs when there is a disaster of some sort that reduces a population to a small handful, which rarely represents the actual genetic makeup of the initial population This leaves smaller variation among the surviving individuals.

Genetic drift - The Founder Effect

Adaptive Radiation Process in which organisms diversify rapidly from an ancestral species into a multitude of new forms Particularly when a change in the environment makes new resources available, creates new challenges, or opens new environmental niches

Homologous Structures:  parts of the body that are similar in structure to other species' comparative parts

Convergent Evolution Process whereby organisms not closely related independently evolve similar traits as a result of having to adapt to similar environments or ecological niches

Coevolution: when changes in at least two species' genetic compositions reciprocally affect each other's evolution

Vestigial organs/structures Seemingly useless Organs, Structures, and behaviors that appear to have served a functional purpose in the evolutionary history of a species