Natural Selection and Evolution

Understanding Evolution and Natural Selection

Evolution is the process where species of organisms change over time due to changes in their inherited features. It explains the diversity of life on earth.
Natural selection refers to the process by which organisms that are better adapted to their environment survive and reproduce more successfully than others. Charles Darwin and Alfred Wallace proposed this theory.

Process of Natural Selection

All species have the potential to produce more offspring than can survive to adulthood.
Within a population,there is genetic variation. The individuals in a species vary because of differences in their genes.
The food and other resources a population need to survive are limited, creating a struggle for survival.
Those individuals with characteristics most suited to their environment are more likely to survive, and have more offspring. This is the principle of survival of the fittest.
Over time a significant proportion of the population will possess the beneficial characteristic. This evolves through generations.

Evidence for Evolution

Fossil records provide evidence for evolution. Fossils of early organisms show a simple structure; later ones are more complex, showing an increase in complexity over time.
Antibiotic resistance in bacteria is an example of current day evolution. Bacteria that survive antibiotic treatment reproduce, passing on their resistance to their offspring.
Comparison of DNA and protein structure between species can indicate how closely related two species are, supporting the idea of a common ancestry.

Speciation

Speciation is the formation of new and distinct species in the course of evolution.
Geographical isolation can lead to speciation. If a group of animals from a species gets cut off (for example by a river changing course), they become isolated from the rest of the species.
Over time, because of different selection pressures in the different environments, the two groups may become so different that they can no longer interbreed to produce fertile offspring, so are considered separate species.

By understanding these fundamental concepts, individuals can grasp how life on Earth has changed and adapted over time through the process of natural selection and evolution.