The Theory of Evolution

What is Evolution? Evolution is a process by which modern organisms have descended from ancient organisms. It is a change in population and not individuals over long periods of time.

Who is Charles Darwin? An English Naturalist and Geologist best known for his contributions to the Theory of Evolution. In 1831, Darwin set sail from England about the H.M.S. Beagle for a voyage around the world. At which time he made numerous observations and collected evidence that led him to propose a hypothesis about the way life changes over time based on natural selection.

What is Natural Selection? (also known as Survival of the Fittest) Process by which individuals who are better adapted or most fit for their environment will survive and reproduce successfully. In the Galapagos Darwin notices that there were variations among members of the same species. Example: Finches, Giant Tortoise

Example of Natural Selection – Peppered Moths The evolution of the peppered moth over the last two hundred years has been studied in detail. Originally, the vast majority of peppered moths had light coloration, which effectively camouflaged them against the light- colored trees and lichens upon which they rested. However, due to widespread pollution during the Industrial Revolution in England, many of the lichens died out, and the trees which peppered moths rested on became blackened by soot, causing most of the light-colored moths, to die off due to predation

Based on Darwin’s theory, who would be considered “more fit.” Tim Tebow?Mamma June?

Darwin’s thoughts over Evolution were influenced by numerous people such as James Hutton and Charles Lyell (geologists)Thomas Malthus (an economist), and Jean-Baptiste Lamarck ( a naturalist, like Darwin). Thomas Malthus Jean-Baptiste LaMarck

Lamarck’s Idea of Acquired Traits: He proposed that by selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime. He believed that these acquired traits could then be passed on to their offspring which led to a change in a species.

Important Vocabulary for Evolution Evolution = A change in populations and not individuals over long periods of time. Scientific Theory = well-supported, testable explanation of phenomena that have occurred in the natural world. Adaptation: any inherited characteristic that increases an organism’s chances for survival. Fitness: the ability for an organism to survive and reproduce in its environment. It’s a result of adaptation.

ADAPTATIONS

There are 2 types of Adaptation: Camouflage and Mimicry CAMOUFLAGE: An adaptation that allows organisms to blend into their environment. Example: ghekko blending in to avoid predation.

MIMICRY: An adaptation that allows one species to evolve into resembling another species which often results in the species to often increase their fitness ability while also allowing them to escape possible predation. Example: Eastern Coral Snake/Scarlet King Snake or the Monarch/Viceroy Butterflies

Evolutionary Support Complete Your Evidence of Evolution Packet

Genetic Variation

Based on modern knowledge of genetics, we NOW know that natural selection is dependent on genetic variation within the gene pool. Genetic variation allows diversity within a population. Gene Pool: consists of all the genes including all the different alleles that are present in a population. A population is a group of individuals that inhabit the same area. A species is a group of similar organisms that can breed and produce fertile offspring.

Speciation: the formation of a new and distinct species in the course of evolution.

Geographic Isolation: When two populations of a species becomes separated by geographic barriers such as rivers or mountain ranges resulting in the formation of 2 separate gene pools. Allopatric Speciation Ex: Abert Squirrels vs. Kaibab Squirrels.

MECHANISMS OF EVOLUTION Although natural selection remains a central theme in evolution, scientists NOW know that natural selection is NOT the only mechanism for evolution.

One of those mechanisms is called the HARDY-WEINBERG PRINCIPLE which states that when an allele frequency remains constant, a population is in genetic equilibrium. Hardy (mathematician) and Weinberg (physician) both showed mathematically that evolution will not occur in a population unless allele frequencies are acted upon by forces that cause change. There are 5 conditions required to maintain genetic equilibrium: (1). Random mating (2) must have very large population (3) no movement into or out of population (4) no mutations and (5) no natural selection.

Another mechanism is called Genetic Drift a change in allele frequencies that occur in small populations. These changes are associated with random events. There are 2 types of genetic drift: – founder effect small group splinters off & starts a new colony – bottleneck some factor (disaster) reduces population to small number & then population recovers & expands again

diverse population  “catastrophic event” (hunting, earthquake, volcanic eruption, etc.  small % of the original population remains & re-populates  less diverse population Bottleneck Effect Example:

Genetic Drift by way of Founders Effect Small population gets separated by chance (storm, earthquake, etc.) Develop different adaptations over many generations If they come in contact later, they are too different to interbreed Ex. Galapagos finches fly to nearby island

Gene Flow: the transfer of genes or alleles from one population to another.

Gene Flow Movement of individuals & alleles in & out of populations – seed & pollen distribution by wind & insect – migration of animals sub-populations may have different allele frequencies causes genetic mixing across regions reduce differences between populations

Human Evolution Today Gene flow in human populations is increasing today – transferring alleles between populations Are we moving towards a blended world?