Evolution
Change over time or the process by which modern organisms have descended from ancient organisms. In genetic terms, it is the relative frequency of alleles in a population.
Theory
A well-supported testable explanation.
Voyage of the Beagle
During his travels, Darwin made numerous observations and collected evidence that led him to propose a revolutionary hypothesis about the way life changes over time.
Charles Darwin
Born in England on February 12, 1809, the same day as Abraham Lincoln. Shortly after completing his college studies, Darwin joined the crew of the Beagle . In 1831 he set sail from England for a voyage around the world. It was one of the most important vo
Fossils
The preserved remains of ancient organisms.
The Galapagos Islands
Observed the Tortoise shell variation between Tortoises of different islands. Studied birds and the differences between beak size.
The Journey Home
While heading home, Darwin spent a lot of time thinking about his findings and examining different mockingbirds from the Galapagos. Darwin noticed that the individual birds collected from the island of Floreana looked different from individuals collected
James Hutton
1785. Hutton proposes that Earth is shaped by geological forces that took place over extremely long periods of time. He estimates the earth to be millions-not thousands-of years old.
Thomas Malthus
1798. In his Essay on the Principles of Population, Malthus predicts that the human population will grow faster then the space and food supplies needed to sustain it.
Jean-Baptiste Lamarck
1809. Lamarck publishes his hypotheses of the inheritance of acquired traits. The ideas are flawed, but he is one of the first to propose a mechanism explaining how organisms change over time.
Charles Lyell
1833. In the second and final volume of Principles of Geology, Lyell explains that processes occurring now have shaped Earth's geological features over long periods of time. Lyell's work explained how awesome geological features could be built up or torn
Alfred Wallace
1858. Wallace writes to Darwin, speculating on evolution by natural selection, based on his studies of the distribution of plants and animals.
On the Origin of Species
Darwin's book on evolution published in1859.
Lamarck's Evolution Hypotheses
Lamarck proposed that by selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime. These traits could then be passed on to their offspring. Over time, this process led to change in a species.
Tendency Toward Perfection
Lamarck proposed that al organisms have an innate tendency toward complexity and perfection. As a result, they are continually changing and acquiring features that help them live more successfully in their environments.
Use and Disuse
Because of this tendency toward perfection, Lamarck proposed that organisms could alter the size or shape of particular organs by using their bodies in new ways.
Inheritance of Acquired Traits
Like many biologists of his time, Lamarck thought that acquired characteristics could be inherited. FALSE
Population Growth
Malthus reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone.
Artificial Selection
Nature provided the variation and humans selected those variations that they found useful.
The Struggle for Existence
The members of each species compete regularly to obtain food, living space, and other necessities of life.
Fitness Adaption
Any inherited characteristic that increases an organism's chance of survival.
Survival of the Fittest
Individuals that are better suited for the environment survive and reproduce most successfully.
Natural Selection
Survival of the Fittest: Individuals that are better suited for the environment survive and reproduce most successfully.
Over time, natural selection results in changed in the inherited characteristics of a population. These changed increase a species' fi
Descent with Modification
Each living species has descended, with changes, from other species over time.
Common Descent
If we look far enough back, we could find common ancestors of all living things.
Evidence of Evolution
Darwin argued that living things have been evolving for millions of years. Evidence for this process could be found in the fossil record, the geographical distribution of living species, homologous structures of living organisms, and similarities in early
Homologous Body Structures
Structures that have different mature forms but develop from the same embryonic tissues.
Vestigial Organs
The organs of many animals are so reduced in size that they are just vestiges, or traces, of homologous organs in other species.
Darwin's Theory
Individual organisms differ, and some of this variation is heritable.
Organisms produce more offspring than can survive, and many that do survive do not reproduce.
Because more organisms are produced than can survive, they compete for limited resources.
E
Gene Pool
Consists of all genes, including all the different alleles, that are present in a population.
Relative Frequency (of an allele)
The number of times that the allele occurs in a gene pool, compared with the number of times other alleles for the same gene occur.
Mutations
A source of genetic variation. Any change in a sequence of DNA. Mutations can occur because of mistakes in the replication of DNA or as a result of radiation or chemicals in the environment. Mutations do not always affect an organisms phenotype.
Gene Shuffling
A source of genetic variation. You do not look exactly like your parents even thought hey provided you with all your genes. Most heritable differences are due to gene shuffling that occurs in the production of gametes.
Single-gene Trait
A form of Heritable Variation. Ex. widow's peak. It is controlled by a single gene that has two alleles. The number of phenotypes produced for a given trait depends on how many genes control the trait.
Polygenic Traits
Traits controlled by two or more genes. Bell shaped curve.
Natural Selection on Single-Gene Traits
Can lead to changes in allele frequencies and this to evolution.
Natural Selection on Polygenic Traits
Can affect the distributions of phenotypes in any of three ways: Directional Selection, Stabilizing Selection, or Disruptive Selection.
Directional Selection
When individuals at one end of the curve have a higher fitness than individuals in the middle or at the other end. Ex. Birds whose beaks enable them to open those larger seeds will have better access to food. Birds with the big-beak adaption would therefo
Stabilizing Selection
When individuals near the center of the curve have higher fitness than individuals at either end of the curve. This situation keeps the center of the curve at its current position, but it narrows the overall graph. Ex. Human babies born much smaller than
Disruptive Selection
When an individual at the upper and lower ends of the cure have higher fitness than individuals near the middle. Ex. A population of birds lives in an area where medium-sized seeds become less common and large and small sees become more common. Birds with
Genetic Drift
Random change in allele frequency. A source of evolutionary change.
Founder Effect
A situation in which allele frequencies change as a result of the migration of a small subgroup of a population.
Hardy-Weinberg Principle
States that allele frequencies in a population will remain constant unless one or more factors cause those frequencies to change.
Genetic Equilibrium
The situation in which allele frequencies remain constant. Five conditions are required to maintain this from generation to generation: 1) There must be random mating;2) The population must be very large; and 3) There can be no movement into or out of the
Speciation
The formation of new species.
Reproductive Isolation
A type of isolating mechanism.When the members of two offspring cannot interbreed and produce fertile offspring. As new species evolve, populations become reproductively isolated from each other.
Behavioral Isolation
A type of isolating mechanism. Occurs when two populations are capable of interbreeding but have differences in courtship rituals or other reproductive strategies that involve behavior.
Geographic Isolation
A type of isolating mechanism. Occurs when two populations are separated by geographic barriers such as rivers, mountains, or bodies of water.
Temporal Isolation
A type of isolation mechanism. Occurs when two or more species reproduce at different times.
Speciation in Darwin's Finches
Speciation in the Galapagos finches occurred by founding of a new population, geographic isolation, changes in the new population's gene pool, reproductive isolation, and ecological competition.