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- 1From:The Gale Encyclopedia of Science (Vol. 6. 6th ed.)Punctuated equilibrium is a theory about how new species evolve that was first advanced by American paleontologists Niles Eldredge (1943–) and Stephen Jay Gould (1941–2002) in 1972. Although controversial, punctuated...
- 2From:The Gale Encyclopedia of Science (Vol. 4. 6th ed.)Often referred to as a living fossil, the horseshoe crab has changed relatively little morphologically over the past 450 million years. The large greenish brown, helmet-like dorsal plate, called either the cephalothorax...
- 3From:The Gale Encyclopedia of Science (Vol. 3. 6th ed.)A gene mutation refers to a change in the building blocks (nucleotides) that specify the sequence of a gene. A gene mutation can enhance, impair, or completely block a gene's activity. There are many different types of...
- 4From:The Gale Encyclopedia of Science (Vol. 2. 6th ed.)Chemical evolution is the sequence of chemical changes in originally nonliving matter that give rise to life. The phrase “chemical evolution” is also used, in astronomy and cosmology, to describe the changing makeup of...
- 5From:The Gale Encyclopedia of Science (Vol. 6. 6th ed.)Paleobotany endeavors to reconstruct past climates and regional vegetation systems by studying the fossilized remains of plants or preserved pollen samples. Such studies have yielded information regarding global climate...
- 6From:The Gale Encyclopedia of Science (Vol. 4. 6th ed.)An individual, in the sense of evolutionary biology, is a genetically unique organism. An individual has a complement of genetic material, encoded in its DNA (deoxyribonucleic acid), that is different from other members...
- 7From:The Gale Encyclopedia of Science (Vol. 4. 6th ed.)An island is a land mass smaller than a continent and is completely surrounded by water. That distinction, although somewhat artificial, suggests that different geologic forces act to create and maintain islands versus...
- 8From:The Gale Encyclopedia of Science (Vol. 1. 6th ed.)Astrobiology is the area of life science that investigates the origin of life, how the biological components interact to create an environment, and what makes planets habitable. It also searches for life on other...
- 9From:The Gale Encyclopedia of Science (Vol. 3. 6th ed.)Rates of evolution change vary widely, among characteristics and among species. Evolutionary rate of change can be estimated by examining fossils and species that are related to each other. The rate of change is governed...
- 10From:The Gale Encyclopedia of Science (Vol. 3. 6th ed.)That all existing varieties of life have evolved from simpler, interrelated ancestors is one of the most solidly established facts known to modern science, and it is the basis of all modern biological science. Evidence...
- 11From:The Gale Encyclopedia of Science (Vol. 3. 6th ed.)Evolution is the process by which new living forms arise naturally over long periods of time. Such changes are driven by several evolutionary mechanisms. Evolutionary mechanisms also explain relatively rapid changes...
- 12From:The Gale Encyclopedia of Science (Vol. 3. 6th ed.)Evolution is the natural process by which all living things have descended with modifications from shared ancestors, shaped largely by natural selection. It involves change in the genetic constitution of populations over...
- 13From:The Gale Encyclopedia of Science (Vol. 6. 6th ed.)Paleoecology is the branch of paleontology that studies ancient organisms and their environments. Paleoecologists study the physical structure and biological functions of organisms, their interactions with each other,...
- 14From:The Gale Encyclopedia of Science (Vol. 6. 6th ed.)Primates refer to animals that share many similarities with humans, including approximately 98% of the genome (the total collection of genetic material that encodes the organism). These near-identical genomes argue...
- 15From:The Gale Encyclopedia of Science (Vol. 3. 6th ed.)Exponents are numbers that indicate the operation of exponentiation on a number or variable. In the simplest case, an exponent that is a positive integer indicates that multiplication of a number or variable is to be...
- 16From:The Gale Encyclopedia of Science (Vol. 6. 6th ed.)Phylogeny is the inferred evolutionary history of a group of organisms. Paleontologists are interested in understanding the relationships between different species over long periods of past time. In order to reconstruct...
- 17From:The Gale Encyclopedia of Science (Vol. 5. 6th ed.)There is no direct fossil evidence of how life began on Earth. Such evidence could not exist: the molecular processes that scientists believe preceded the appearance of cells could not have left imprints on rock....
- 18From:The Gale Encyclopedia of Science (Vol. 1. 6th ed.)Life on Earth can be divided into three large collections, or domains. These are the Eubacteria (or “true” bacteria), Eukaryota (the domain that humans belong to), and Archae. The members of this last domain are the...
- 19From:The Gale Encyclopedia of Science (Vol. 1. 6th ed.)There are many forms of evidence for evolution. One of the strongest is comparative anatomy; comparing structural similarities of organisms to determine their evolutionary relationships. Organisms with similar anatomical...
- 20From:The Gale Encyclopedia of Science (Vol. 5. 6th ed.)Extinction, the death of all members of a species, is a natural process that has been occurring since the beginning of life on Earth. Nearly all species that have ever existed are now extinct—about 99.9% of them—and...