Fossil
Any preserved evidence of an organism./
Paleontologist
Scientist who studies fossils./
Relative dating
method used to determine the age of rocks by comparing them with those in other layers./
Law of superposition
states that younger layers of rock are deposited on top of older layers./
Radiometric Dating
uses the decay of radioactive isotopes to measure the age of a rock./
Half-life
amount of time it take for half of the original isotope decay./
Geologic time scale
record of Earth's history./
Epochs
Smallest units of geologic time./
Periods
Divisions of geologic time consisting of two or more epochs./
Era
unit of geologic time consisting of two or more periods/
Eon
Longest unit of geologic time./
Cambrian explosion
Space of a few million years in which most major animal groups diversified./
K-T boundary
layer of meteorite rock between Cretaceous rock and Paleogene rock./
Plate Tectonics
movement of several large plates that make up the surface of the earth./
Spontaneous Generation
idea that life arises form non-life/
Theory of Biogenesis
only living organisms can produce other living organisms./
Endosymbiont theory
idea that ancestors of eukaryotic cells lived in association with prokaryotic cells./
Artificial selection
process of directed breeding to produce offspring with desired traits; referred to as selective breeding./
Natural selection
theory of evolution developed by Darwin, based on four ideas; excess reproduction, variations, inheritance, and the advantages of specific traits in an environment./
Evolution
cumulative changes in groups of organisms through time./
Derived trait
newly evolved features that do not appear in the fossils of common ancestors./
Ancestral trait
primitive features that do appear in ancestral forms./
Homologous structure
anatomically similar structures inherited from a common ancestor./
Vestigial structure
structures that are the reduced forms of functional structures i other organisms./
Analogous structure
structures that are used for the same purpose and can be superficially similar in construction but are not inherited form a common ancestor./
Embryo
an early pre-birth stage of an organism's development./
Biogeography
study of the distribution of plants and animals around the world./
Fitness
measure of the relative contribution that an individual trait makes to the next generation./
Camouflage
evolved morphological adaptations that allow an animal to blend in with their environment./
Mimicry
a morphological adaptation in which one species evolves to resemble another species./
Hardy-Weinberg principle
Idea that when allele frequencies remain constant, a population is in genetic equilibrium./
Genetic drift
change in the allele frequency of a population as a result of chance events rather than natural selection./
Founder effect
Genetic drift that occurs after a small number of individuals colonize a new area./
Bottleneck
change in allele frequency following a dramatic reduction in the size of a population./
Stabilizing selection
Natural selection in which intermediate phenotypes survive or reproduce more successfully than do extreme phenotypes./
Directional selection
Pathway by which one extreme phenotype is chosen over a common phenotype./
Disruptive selection
form of natural selection in which a single curve splits into two; occurs when individuals at the upper and lower ends of a distribution curve have higher fitness than individuals near the middle./
Sexual selection
when individuals select mates based on heritable traits./
Prezygotic isolating mechanisms
type of reproductive isolating mechanism preventing gene flow before fertilization./
Postzygotic isolating mechanisms
Occurring after formation of a zygote./
Allopatric speciation
When a population is divided; leads to speciation./
Sympatric speciation
Speciation without a divided population./
Adaptive radiation
An evolutionary pattern in which many species evolve from a single ancestral species./
Gradualism
The theory that evolution occurs slowly but steadily./
Punctuated equilibrium
Pattern of evolution in which long stable periods are interrupted by brief periods of more rapid change./