Galton, Francis: A cousin of Charles Darwin, Galton was a British explorer and anthropologist. He was known for his studies of human intelligence and later for his work in eugenics (a term he coined), the "science" of improving human hereditary characteristics. Known for his efforts at various sorts of measurement (he developed fingerprinting and was a pioneer in statistics), he was knighted in 1909.
gamete: Haploid reproductive cells that combine at fertilization to form the zygote, called sperm (or pollen) in males and eggs in females.
gastropod: Meaning "stomach foot," this name refers to the class of mollusks that contains the most species. Gastropods include snails and slugs that are marine, freshwater, and terrestrial.
Gehring, Walter J.: Dr. Gehring and his research group discovered the homeobox, a DNA segment characteristic for homeotic genes which is not only present in arthropods and their ancestors, but also in vertebrates up to humans. Their work on the "master control gene" for eye development sheds light on how the mechanism for building eyes may have evolved long ago in the ancestor of what are now very different types of organisms.
gene: A sequence of nucleotides coding for a protein (or, in some cases, part of a protein); a unit of heredity.
genetic: Related to genes. A gene is a sequence of nucleotides coding for a protein (or, in some cases, part of a protein); a unit of heredity.
genetics: The study of genes and their relationship to characteristics of organisms.
genetic code: The code relating nucleotide triplets in the mRNA (or DNA) to amino acids in the proteins.
genetic distance: See distance.
genetic drift: Changes in the frequencies of alleles in a population that occur by chance, rather than because of natural selection.
genetic engineering: Removing genes from the DNA of one species and splicing them into the DNA of another species using the techniques of molecular biology.
genetic load: A reduction in the average fitness of the members of a population because of the deleterious genes, or gene combinations, in the population. It has many particular forms, such as "mutational load," "segregational load," and" recombinational load."
genetic locus: See locus.
gene duplication: See duplication.
gene family: A set of related genes occupying various loci in the DNA, almost certainly formed by duplication of an ancestral gene and having a recognizably similar sequence. Members of a gene family may be functionally very similar or differ widely. The globin gene family is an example.
gene flow: The movement of genes into or through a population by interbreeding or by migration and interbreeding.
gene frequency: The frequency in the population of a particular gene relative to other genes at its locus. Expressed as a proportion (between 0 and 1) or percentage (between 0 and 100 percent).
gene pool: All the genes in a population at a particular time.
genome: The full set of DNA in a cell or organism.
genomics: The study that characterizes genes and the traits they encode.
genotype: The set of two genes possessed by an individual at a given locus. More generally, the genetic profile of an individual.
genus (plural genera): The second-to-lowest category in taxonomic classification. The phrase "species name" generally refers to the genus and species together, as in the Latin name for humans, Homo sapiens. See taxon.
geographic isolation: See reproductive isolation.
geographic speciation: See allopatric speciation.
geologic time: The time scale used to describe events in the history of Earth.
germination: The initial stages in the growth of a seed to form a seedling. The embryonic shoot (plumule) and embryonic root (radicle) emerge and grow upward and downward, respectively. Food reserves for germination come from tissue within the seed and/or from the seed leaves (cotyledons).
germ plasm: The reproductive cells in an organism, or the cells that produce the gametes. All cells in an organism can be divided into the soma (the cells that ultimately die) and the germ cells (the cells that are perpetuated by reproduction).
gestation: The period in animals bearing live young (especially mammals) from the fertilization of the egg and its implantation into the wall of the uterus until the birth of the young (parturition), during which the young develops in the uterus. In humans gestation is known as pregnancy and takes about nine months (40 weeks).
Gingerich, Philip: Gingerich is interested in evolutionary change documented in the fossil record and how this relates to the kinds of changes observable in the field or laboratory on the scale of a few generations. His ongoing fieldwork in Wyoming, Egypt, and Pakistan is concerned with the origin of modern orders of mammals, especially primates and whales.
glaciation: The formation of large sheets of ice across land. Glaciation of the continents marks the beginning of ice ages, when the makeup of Earth and organisms on it changes dramatically.
Goldfarb, Alex: A Russian-born microbiologist now at the Public Health Research Institute in New York City, Dr. Goldfarb is piloting a program in the Russian prison system to combat the further evolution of drug-resistant strains of tuberculosis, which have infected at least 30,000 inmates.
Gould, Stephen Jay: A professor of geology and zoology at Harvard University since 1967. A paleontologist and an evolutionary biologist, he teaches geology and the history of science, as well. With others, he has advanced the concept that major evolutionary changes can occur in sudden bursts rather than through the slow, gradual process proposed by the traditional view of evolution. In addition to his scholarly works, Gould has published numerous popular books on paleoanthropology, Darwinian theory, and evolutionary biology.
Grant, Peter and Rosemary: Biologists whose long-term research focuses on finches in the Galapagos Islands, and the evolutionary impact of climatic and environmental changes on their populations. They live part of the year in the Islands, and have received honors for their work since they began in 1973.
graptolite: A small, colonial, often planktonic marine animal that was very abundant in the oceans 300 to 500 million years ago; now extinct.
Greene, Mott: A historian of science who has written extensively about the development of geological thought during the 19th and early 20th centuries ,including the development of the theory of continental drift.
greenhouse gases: Gases that absorb and reradiate infrared radiation. When present in the atmosphere, these gases contribute to the greenhouse effect, trapping heat near the surface of the planet. On Earth, the main greenhouse gases are carbon dioxide, water vapor, methane, nitrous oxide, ozone, and some halocarbon compounds.
group selection: The selection operating between groups of individuals rather than between individuals. It would produce attributes beneficial to a group in competition with other groups rather than attributes beneficial to individuals.