Darwin Developed a Theory of Evolution Concept 14.1 Darwin Developed a Theory of Evolution

Ideas from Darwin’s Time A new view of life came into focus in 1859, when Charles Darwin published his book the Origin of Species, Darwin’s ideas provided a framework for understanding Earth’s diversity of organisms and their relationships to one another and their environment.

Evolution Generation-to-generation change in the proportion of different inherited genes in a population that accounts for all changes that have transformed life over an immense time.

Adaptation An inherited characteristic that improves an organism’s ability to survive and reproduce in a particular environment.

The Voyage of the H.M.S. Beagle The intent of the voyage in 1831 was to set sail and chart stretches of the South American coast. Darwin’s job was to document the plants, animals and geology encountered during the voyage, but more came from it.

The Galapagos Islands This is an island area about 600 miles of the coast of South America. Here Darwin made many observations. There were many unique animals here that were similar but different from the animals on the mainland.

Descent with Modification He proposed that the descendants of the earliest organisms spread into various habitats over millions of years. In these habitats, they accumulated different modifications or adaptations to diverse ways of life.

Natural Selection It is the process by which individuals with inherited characteristics well suited to the environment leave more offspring on average than do other individuals. Key to natural selection is offspring is not power or speed, although this will help.

Concept 14.2 Evolution has left much evidence.

Fossils Preserved remains or markings left by organisms that lived in the past.

Fossil Record It is the chronological collection of life’s remains in the rock layers, recorded during the passage of time.

Extinct These are species that no longer exists on Earth.

Similarities in Structure Homologous vs. Analogous

Homologous Structures These are characteristics that share a common ancestor. The limbs of the following organisms: Human Cat Whale Bat

Analogous Structures These are structures that share no common ancestor. Wings of a bird and the wings of a bat.

Population Genetics It is the study of evolution from a genetic point of view.

Microevolution It is defined as a change in the collective genetic material of a population. (Alleles)

Bell Curve It is a graph of the frequency of a particular occurrence.

Gene Pool It is a term used to describe the total genetic information available in a population.

Allele Frequency How often an allele occurs in a population.

Phenotypic Frequency It is equal to the number of individuals with a particular phenotype divided by the total number of individuals in the population.

Immigration It is the movement of individuals into a population.

Emigration It is the movement of individuals out of a population.

Gene Flow It is the process of genes moving from one population to another.

Sexual Selection Possessing traits that favor the opposite sex for reproductive means.

Stabilizing Selection Individuals with the average form of a trait have the highest fitness.

Disruptive Selection Individuals with either extreme variation of a trait have a greater fitness than individuals with the average form of the trait.

Directional Selection Individuals that display a more extreme form of the trait have a greater fitness than individuals with an average form of the trait.

Speciation The process of species formation.

Geographic Isolation It is the physical separation of members of a population.

Allopatric Speciation This happens when species arise as a result of geographic isolation.

Reproductive Isolation It results from barriers to successful breeding between population groups in the same area.

Sympatric Speciation It occurs when two subpopulations become reproductively isolated within the same geographic area.

Gradualism The idea that speciation occurs at a regular, gradual rate.

Punctuated Equilibrium It refers to a sudden rapid change.