Natural Selection The process by which organisms that are better suited to their environment than others produce more offspring.

As a result of natural selection, the proportion of organisms in a species with characteristics that are adaptive to a given environment increases with each generation. Therefore, natural selection modifies the originally random variation of genetic traits in a species so that alleles that are beneficial for survival predominate, while alleles that are not beneficial decrease.

Species basic category of biological classification, composed of related individuals that resemble one another, are able to breed among themselves, but are not able to breed with members of another species.

Selective Pressure Environmental pressures on populations; drought, climate change, new predator,… Selective pressure can cause some individuals to fail or produce few offspring while others survive and produce large numbers of offspring. The pressure selects which individuals will survive and which will fail.

“Survival of the fittest” The organisms with adaptations that allow it to acquire resources and reproduce more effectively than another is the one that will survive. OR “Survival of the fittest” thus means the organisms that fit best with their surroundings will thrive and reproduce.

Content Statement Diversity of species occurs through gradual processes over many generations. Fossil records provide evidence that changes have occurred in number and type of species.

Content Statement cont. Fossils provide important evidence of how life and environmental conditions have changed.

Content Statement cont. Changes in environmental conditions can affect how beneficial a trait will be for the survival and reproductive success of an organism or an entire species.

Content Statement cont. Throughout Earth’s history, extinction of a species has occurred when the environment changes and the individual organisms of that species do not have the traits necessary to survive and reproduce in the changed environment. Most species (approximately 99 percent) that have lived on Earth are now extinct.

Extinction The dying out or termination of a species. Extinction occurs when species are diminished because of environmental factors or because of evolutionary changes in their members (genetic inbreeding, poor reproduction, decline in population numbers).

Mass Extinctions

An adaptation is a trait that allows an organism to survive An adaptation is a trait that allows an organism to survive. Adaptations are due to natural selection and the changing of environments that favors one trait over another. Variation in a population can eventually lead to adaptation if there is a selecting factor. An example of an adaptation is color adaptation. Animals that are harmless mimic the color schemes of dangerous animals to protect themselves. (Snakes) (Youtube-https://www.youtube.com/watch?v=L4tJ3bYmfxw)

The adaptations we see today are the “happy accidents,” the ones that worked to the organism’s advantage and helped it survive. Adaptations determine the relationships organisms have with their environment.

It is possible for offspring to vary somewhat from their parents, as well as from their siblings. The variation may or may not contribute to the improved survival of the individual sporting the variation

The fossil record documents the variation in a species that may have resulted from changes in the environment. The fossil record is contained within the geologic record (ESS grade 8). Combining data from the geologic record and the fossil record, Earth’s living history can be interpreted.

Charles Darwin