Paleontologists

Sciensts who conduct studies of fossils.

Paleozoic Era

An era which lasted from 545 million years ago to 245 million years ago in the earth's history. It consists of the Cambrian Period, Ordovician Period, Silurian Period, Devonian Period, and Carboniferous (Mississipian/Pennsylvanian) Period.

Parallel Evolution

An evolutionary pattern that describes two related species or lineages that have made similar evolutionary changes after their divergenece from a common ancestor.

Parapatric Speciation

The formation of a new species between populations of a continuous cline.

Permian Period

A period of the earth's history lasting from 286 million years ago to 245 million years ago

Phenotype

The appearance of an organism as a result of its genetic material and allelic combinations.

Photosynthesis

A food-making process that occurs in green plants. Green plants use energy from light to combine carbon dioxide and water to make food.

Phyla

A direct line of descent, usually within a species.

Phyletic Gradualism

Macroevolutionary theory that evolution occurs by the gradual accumulation of small changes.

Phylogeny

The evolutionary history of development of an animal or plant species.

Phylum

A unit of scientific classification which comes after order but before species in terms of biological relationships.

Physiology

The study of the functions of living things.

Pleistocene

An epoch of time lasting from 2 million to 10,000 years ago in the earth's history. More commonly known as the Ice Age.

Pliocene

An epoch of time lasting from 7 million to 2 million years ago in the earth's history.

Polyploidy

A gain of one or more entire sets of chromosomes; the formation of a new species via such a gain.

Population

The number or amount of organisms in a community (or species).

Postzygotic Reproductive Isolating Mechanism

Reproductive isolating mechanism that takes effect after fertilization by reducing the fertility of hybrids or their progeny.

Precambrian Era

A period of time that lasted from 5 billion years ago to 545 million years ago in the earth's history. Consists of the Archaeozoic (Archean) Era and the Proterozoic Era.

Prezygotic Reproductive Isolating Mechanism

Reproductive isolating mechanism that takes effect before fertilization via ecological, temporal, behavioral, mechanical, morphological, and gametic isolation.

Primate

Primates are members of the group of mammals made up of human beings and the animals that resemble them most closely. They make up the order Primates in the class Mammalia.

Proteins

Substances made up of amino acids. A cell's structures are built chiefly of proteins.


Proterozoic Era

An era in the earth's history lasting from 2.5 billion years ago to 545 million years ago. It is marked by the emergence of advanced multicellular life.

Punctuated Equilibrium

Macroevolutionary theory which argues that evolutionary history consists of long periods of time of little or no evolution, which are "punctuated," or interrupted, by very short periods of quick evolution.