Natural Selection and Adaptation

• Camels survive in desert environments due to long, bushy eyelashes and closable nostrils.
• Giraffes can reach the leaves of tall trees due to their long legs and necks.

The Theory of Natural Selection

• Evolution is the change in the adaptive features of populations over time
• Natural selection is the process by which the fittest individuals are more likely to survive and reproduce.
• Adaptation is the process by which populations become more suited to their environment over generations.
• Charles Darwin’s theory of evolution by natural selection was published in 1859 in On the Origin of Species.
• Variations exist naturally among individuals within a population
• Some trait forms make individuals more or less fit to the environment
• More offspring are generally produced than the environment can support, referred to as overproduction.
• Due to limited resources, organisms compete to survive.
• Individuals adapted to their environment have a survival advantage.
• Well-adapted organisms are more likely to survive, reproduce, and pass on adaptive features.
• Less adapted individuals are less likely to survive and may disappear from the population.
• Evolution results in traits that suit individuals to their environment becoming common.
• Traits with little survival advantage become less common, potentially leading to new species.
• Natural selection: factors in an organism's environment may favor or disfavor specific trait forms.
• Changing environmental conditions can cause species to change and evolve over time
• Inherited adaptive features make an organism more fit, encoded by genes
• Alleles for advantageous phenotypes are frequently passed from parents to offspring versus less advantageous phenotypes.

Peppered Moth Example

• Peppered moths are a common example of natural selection.
• Before the industrial revolution in Great Britain, light-colored speckled moths were more common as birds could not see them on lichen-covered tree trunks.
• Birds easily spotted dark-colored ones.
• Predation by birds is an example of selection pressure, which leads to the selection of a trait that improves an organism’s survival.
• Speckled wings gave the moths a survival advantage over dark-colored wings.
• The industrial revolution caused dark-colored moths to become more numerous in industrial areas
• Local industry polluted woodlands with soot, killing lichens
• Tree trunks turned dark, so dark-colored moths blended in while speckled moths became more easily spotted by birds.
• Predation by birds caused moths with dark-colored wings to have a survival advantage and become more common
• The dark-colored moths reproduced at higher rates and eventually outnumbered speckled moths.
• The allele coding for dark-colored wings became more frequent because it produced an advantageous phenotype.

Explore natural selection: how environmental pressures favor certain traits, leading to adaptation and evolution over generations. Understand Darwin's concepts of variation, overproduction, and competition. Discover how advantageous traits enhance survival and reproduction.