Kegl, Judy: A linguist who works on theoretical linguistics as it applies to signed and spoken languages. Among her research interests is a study of Nicaraguan Sign Language.
Kimbel, Bill: An anatomist, Kimbel worked with Don Johanson and assembled Lucy's skull fragments. In 1991, Kimbel and Yoel Rak found a 70 percent complete skeleton of Australopithecus afarensis.
kingdom: The second highest level of taxonomic classification of organisms (below domains). Classification schemes at the kingdom level have changed overtime. Recent molecular data have generally reinforced the evolutionary significance of the kingdoms Animalia, Plantae, and Fungi. The single-celled eukaryotes once lumped into the kingdom Protista are now known to be very diverse, and not closely related to one another. The prokaryotic organisms once lumped into the kingdom Monera are now considered to belong to separate domains: Eubacteria and Archaea. See taxon.
Kirchweger, Gina: An Austrian biologist interested in the biological evolution of skin tone. Her essay, "The Biology of Skin Color," concerns the evolution of race.
Kluger, Matthew: A researcher whose work on lizards demonstrated that fever is beneficial and can improve the immune response to infection. The implication for humans is still being researched, but evidence indicates that mild fevers can have a number of important immunological functions that allow us to better fight bacterial and viral infections.
Knowlton, Nancy: Dr. Knowlton is professor of marine biology at the Scripps Institution of Oceanography, University of California San Diego, and staff scientist at the Smithsonian Tropical Research Institute in Panama. Her primary research interests concern various facets of marine biodiversity. These include the nature of species boundaries in corals, elucidating biogeographic patterns in tropical seas, the ecology of coral-algal symbiosis, and threshold effects in coral reef ecosystems.
Kondrashov, Alexey: A population geneticist specializing in mathematical analysis who has studied the evolutionary role of slightly deleterious mutations. He has theorized that a primitive organism's strategy for protecting itself against damaging mutations may have been the first step in the evolution of sexual reproduction.
Kreiswirth, Barry: Director of the Public Health Research Institute TB Center in New York, Dr. Kreiswirth uses DNA fingerprinting to study the evolution of antibiotic resistance in Mycobacterium tuberculosis, the pathogen that causes TB.
Lamarckian inheritance: Historically misleading synonym for inheritance of acquired characteristics.
Lamarck, Jean: An 18th-century naturalist, zoologist, and botanist noted for hisstudy and classification of invertebrates, as well as his evolutionary theories. He traveled extensively throughout Europe and was elected to the Academy of Sciences, where he introduced the principles of heredity and acquired characteristics.
land bridge: A connection between two land masses, especially continents (e.g., the Bering land bridge linking Alaska and Siberia across the Bering Strait) that allows migration of plants and animals from one land mass to the other. Before the widespread acceptance of continental drift, the existence of former land bridges was often invoked to explain faunal and floral similarities between continents now widely separated. On a smaller scale, the term may be applied to land connections that have now been removed by recent tectonics or sea-level changes (e.g., between northern France and southeastern England).
larva (and larval stage): The prereproductive stage of many animals. The term is particularly apt when the immature stage has a different form from the adult. For example, a caterpillar is the larval stage of a butterfly or moth.
law: A description of how a natural phenomenon will occur under certain circumstances.
Leakey, Maeve: A paleoanthropologist at the National Museums of Kenya, Maeve is the discoverer of Kenyanthropus platyops and Australopithecus anamensis. She is married to Richard Leakey.
Leakey, Mary: A British paleoanthropologist described as "a real fossil hunter" and "the real scientist in the family." Her discoveries, some in collaboration with her husband Louis Leakey, included the 1.75-million-year-old skull which first showed the antiquity of hominids in Africa, jaws and teeth of an earlyHomo species, and fossilized footprints of bipedal hominids.
Leakey, Richard: The son of renowned anthropologists Louis and Mary Leakey, Richard continued their work on early hominids from 1964 until the 1980s, making a number of significant fossil finds in the Lake Turkana area and serving as director of the National Museum of Kenya. Later he devoted his energies to conservation and politics.
Lee, Melanie: A molecular geneticist and microbial biologist, who in the 1980s collaborated with Paul Nurse on novel research that demonstrated the commonality of the genetic code between yeasts and humans. Dr. Lee later took her molecular skills into the pharmaceutical industry, and was a leader in moving pharmacology away from animal models and toward the use of recombinant DNA technology for screening potential new therapies. She now heads the research division of Celltech, an international biopharmaceutical company, where her team works on drug discovery and development of new therapies, mainly for the treatment of inflammatory and immune diseases.
lek: An area of ground divided into territories that are defended by males for the purpose of displaying to potential mates during the breeding season. This form of mating behavior is known as lekking, and occurs in various bird species (for example the peacock) and also in some mammals. The dominant males occupy the territories at the centre of the lek, where they are most likely to attract and mate with visiting females. The outer territories are occupied by subordinate males, who have less mating success. Over successive breeding seasons, younger subordinate males tend to gradually displace older individuals from the most desirable territories and become dominant themselves. The lek territories do not contain resources of value to the female, such as food or nesting materials, although males of some species may build structures such a sbowers that form part of their display.
lemur: A small, tree-dwelling primate that belongs to the group called prosimians.
lethal recessive: The case in which inheriting two recessive alleles of a gene causes the death of the organism.
Levine, Michael: Professor of genetics and development in the Molecular and CellBiology Department at University of California, Berkeley. Levine was the discoverer (with Bill McGinnis) of homeobox sequences in the homeotic genes Antennapedia and Ultrabithorax while a postdoctoral researcher with Walter Gehring at the University of Basel, Switzerland. His current research involves analysis of gene regulation and patterning in the early Drosophila embryo;s tudies of embryonic development in the tunicate, Ciona intestinalis, focused on the specification of the notochord and tail muscles; and a critical test of classical models for the evolutionary origins of the chordate body plan.
lineage: An ancestor-descendant sequence of (1) populations, (2) cells, or (3)genes. linkage disequilibrium: A condition in which the haplotype frequencies in a population deviate from the values they would have if the genes at each locus were combined at random. (When no deviation exists, the population is said to be in linkage equilibrium.)linked: Of genes, present on the same chromosome.
Linnaean classification: A hierarchical method of naming classificatory groups, invented by the 18th-century Swedish naturalist Carl von Linné, or Linnaeus. Each individual is assigned to a species, genus, family, order, class, phylum, and kingdom, and some intermediate classificatory levels. Species are referred to by a Linnaean binomial of its genus and species, such as Magnolia grandiflora.
Lively, Curtis: A professor of biology who studies population biology and the ecology and evolution of host-parasite interactions. His laboratory is involved in detailed studies of the interaction between a parasitic trematode and a freshwater New Zealand snail in which both sexual and asexual females coexist.
locus: The location in the DNA occupied by a particular gene.
Lovejoy, Owen: A paleoanthropologist and consulting forensic anatomist, Lovejoy is known for his analysis of early hominid fossils. His research includes work on Lucy (Australopithecus afarensis).
lycophyte: Commonly known as club mosses, lycophytes were among the first seedless plants to appear on Earth. Along with horsetails and ferns, these made the planet more hospitable for the first animals.
Lyell's notion of gradual change: Also called uniformitarianism, Lyell's notion was that Earth has been shaped by the same forces and processes that operate today, acting continuously over very long periods of time. For example, the ongoing erosion caused by flowing water in a river could, given enough time, carve out the Grand Canyon.
Lyell, Charles: A 19th-century scientist considered a father of modern geology. Lyell proposed that the geology of Earth is shaped by gradual processes, such as erosion and sedimentation. Lyell's ideas, expressed in his landmark work, Principles of Geology, greatly influenced the young Charles Darwin. Darwin and Lyell later became close friends. While Lyell initially opposed the idea of evolution, he came to accept it after Darwin published On the Origin of Species.
Tuesday, April 21, 2009
Monday, April 20, 2009
Dictionary of Evolutionary Nomenclature - Letters I and J
idealism: The philosophical theory that there are fundamental non-material "ideas," "plans," or "forms" underlying the phenomena we observe in nature. It has been historically influential in classification.
immigration: The movement of organisms into an area.
immutability: The ability to withstand change.
induction: The process of deriving general principles from particular facts.
inference: A conclusion drawn from evidence.
inheritance of acquired characters: Historically influential but factually erroneous theory that an individual inherits characters that its parents acquired during their lifetimes.
insectivorous: Feeding largely or exclusively on insects.
intelligent design: The non-scientific argument that complex biological structures have been designed by an unidentified supernatural or extraterrestrial intelligence.
intron: The nucleotide sequences of some genes consist of parts that code for amino acids, and other parts that do not code for amino acids interspersed among them. The interspersed non-coding parts, which are not translated, are called introns; the coding parts are called exons.
inversion: An event (or the product of the event) in which a sequence of nucleotides in the DNA is reversed, or inverted. Sometimes inversions are visible in the structure of the chromosomes.IQ: An abbreviation of "intelligence quotient," usually defined as the mental age of an individual (as measured by standardized tests) divided by his or her real age and multiplied by 100. This formulation establishes the average IQ as 100. The usefulness and reliability of IQ as a measure of intelligence has been questioned, in part because of the difficulty of devising standardized tests that are free of cultural biases.
isolating mechanism: Any mechanism, such as a difference between species in courtship behavior or breeding season, that results in reproductive isolation between the species.
isolation: Synonym for reproductive isolation.
isotope: An atom that shares the same atomic number and position as other atoms in an element but has a different number of neutrons and thus a different atomic mass.
Jablonski, David: Paleontologist and professor in the Department of the Geophysical Sciences of the University of Chicago. His research emphasizes ombining data from living and fossil organisms to study the origins and fates of lineages and adaptations, to develop an understanding of the underlying dynamics of speciation and extinction that could lead to a general theory of evolutionary novelty. He is interested in the way evolutionary patterns are shaped by the alternation of extinction regimes, with rare but influential mass extinctions driving unexpected evoutionary shifts.
Johanson, Don: A paleontologist and founder of the Institute for Human Origins. Johanson discovered Lucy (at that time the oldest, most complete hominid skeleton known) in 1974, and the following year unearthed the fossilized remains of 13 early hominids in Ethiopia. He is the author of several popular books on human origins.
Johnson, Jerry: Johnson's research interests focus on the interactions and evolutionary relationships of amphibian and reptilian species of tropical American and Mexican desert ecosystems. Johnson specializes in field research in places such as Yucatan, Jalisco, Zacatecas, and Chiapas, Mexico. He has done research on the biochemical analysis of rattlesnake venom using immunological techniques, snake ecology, and lizard ecology.
Johnston, Victor: Professor of biopsychology at New Mexico State University in Las Cruces. His research interests include the evolution of consciousness and perceptions of beauty. He is the author of Why We Feel: The Science of Human Emotions.
immigration: The movement of organisms into an area.
immutability: The ability to withstand change.
induction: The process of deriving general principles from particular facts.
inference: A conclusion drawn from evidence.
inheritance of acquired characters: Historically influential but factually erroneous theory that an individual inherits characters that its parents acquired during their lifetimes.
insectivorous: Feeding largely or exclusively on insects.
intelligent design: The non-scientific argument that complex biological structures have been designed by an unidentified supernatural or extraterrestrial intelligence.
intron: The nucleotide sequences of some genes consist of parts that code for amino acids, and other parts that do not code for amino acids interspersed among them. The interspersed non-coding parts, which are not translated, are called introns; the coding parts are called exons.
inversion: An event (or the product of the event) in which a sequence of nucleotides in the DNA is reversed, or inverted. Sometimes inversions are visible in the structure of the chromosomes.IQ: An abbreviation of "intelligence quotient," usually defined as the mental age of an individual (as measured by standardized tests) divided by his or her real age and multiplied by 100. This formulation establishes the average IQ as 100. The usefulness and reliability of IQ as a measure of intelligence has been questioned, in part because of the difficulty of devising standardized tests that are free of cultural biases.
isolating mechanism: Any mechanism, such as a difference between species in courtship behavior or breeding season, that results in reproductive isolation between the species.
isolation: Synonym for reproductive isolation.
isotope: An atom that shares the same atomic number and position as other atoms in an element but has a different number of neutrons and thus a different atomic mass.
Jablonski, David: Paleontologist and professor in the Department of the Geophysical Sciences of the University of Chicago. His research emphasizes ombining data from living and fossil organisms to study the origins and fates of lineages and adaptations, to develop an understanding of the underlying dynamics of speciation and extinction that could lead to a general theory of evolutionary novelty. He is interested in the way evolutionary patterns are shaped by the alternation of extinction regimes, with rare but influential mass extinctions driving unexpected evoutionary shifts.
Johanson, Don: A paleontologist and founder of the Institute for Human Origins. Johanson discovered Lucy (at that time the oldest, most complete hominid skeleton known) in 1974, and the following year unearthed the fossilized remains of 13 early hominids in Ethiopia. He is the author of several popular books on human origins.
Johnson, Jerry: Johnson's research interests focus on the interactions and evolutionary relationships of amphibian and reptilian species of tropical American and Mexican desert ecosystems. Johnson specializes in field research in places such as Yucatan, Jalisco, Zacatecas, and Chiapas, Mexico. He has done research on the biochemical analysis of rattlesnake venom using immunological techniques, snake ecology, and lizard ecology.
Johnston, Victor: Professor of biopsychology at New Mexico State University in Las Cruces. His research interests include the evolution of consciousness and perceptions of beauty. He is the author of Why We Feel: The Science of Human Emotions.
Dictionary of Evolutionary Nomenclature - Letter H
Haeckel, Ernst: A German biologist who lived from 1834-1919, Haeckel was the first to divide animals into protozoan (unicellular) and metazoan (multicellular) forms. His notion of recapitulation is no longer accepted.
Haile Selassie, Yohannes: A paleoanthropologist who, while doing field work in Ethiopia for his doctoral dissertation at the University of California, Berkeley, discovered Ardipithecus ramidus kadabba, a bipedal hominid dated at5.2 million years old.
half-life: The amount of time it takes for one-half of the atoms of a radioactive material to decay to a stable form. For example, the half-life ofcarbon-14 is 5,568 years.
Hamilton, W.D.: A naturalist, explorer, and zoologist who worked in the world of mathematical models, including "Hamilton's Rule," about the spread through a population of a gene for altruistic self sacrifice. He was also interested in the evolutionary impact of parasites as the key to many outstanding problemsl eft by Darwin, including the baffling riddle of the evolution of sex. This led him to extensive work in computer simulations.
haploid: The condition of having only one set of genes or chromosomes. In normally diploid organisms such as humans, only the gametes are haploid.
haplotype: A set of genes at more than one locus inherited by an individual from one of its parents. It is the multi-locus analog of an allele.
Hardy-Weinberg principle: In population genetics, the idea that if a population experienced no selection, no mutation, no migration, no genetic drift, and random mating, then the frequency of each allele and the frequencies of genotype in the population would remain the same from one generation to the next.
Hardy-Weinberg ratio: The ratio of genotype frequencies that evolve when mating is random and neither selection nor drift are operating. For two alleles (A and a) with frequencies p and q, there are three genotypes: AA, Aa, and aa. The Hardy-Weinberg ratio for the three is: p2AA : 2pqAa : q2aa. It is the starting point for much of the theory of population genetics.
Harvey, Ralph: A geologist whose work includes the study of geological processes at a range of scales, from the smallest nanometer to broader-scale interpretations of the history experienced by geological materials.
heavy metals: Metals with a high relative atomic mass, such as lead, copper, zinc, and mercury. Many of them are toxic.
hemoglobin: A protein that carries oxygen from the lungs throughout the body.
heredity: The process by which characteristics are passed from one generation to the next.
heritability: Broadly, the proportion of variation (more strictly, variance) in a phenotypic character in a population that is due to individual differences in genotypes. Narrowly, it is defined as the proportion of variation (more strictly, variance) in a phenotypic character in a population that is due to individual genetic differences that will be inherited in the offspring.
heritable: Partly or wholly determined by genes; capable of being passed from an individual to its offspring.
Herrnstein, Richard J.: A professor of psychology and an author of notable books on intelligence and crime. He has primarily done research on human and animal motivational and learning processes. His books include Psychology and I. Q. in the Meritocracy, and he coauthored (with Charles Murray) The Bell Curve: Intelligence and Class Structure in American Life (1994).
heterogametic: The sex with two different sex chromosomes (males in mammals ,because they are XY). Compare with homogametic.
heterozygosity: (for most purposes) The proportion of individuals in a population that are heterozygotes.
heterozygote: An individual having two different alleles at a genetic locus. Compare with homozygote.
heterozygote advantage: A condition in which the fitness of a heterozygote is higher than the fitness of either homozygote.
heterozygous: Having two different alleles for a particular trait. See also heterozygote.
Hill, Andrew: A paleontologist and professor at Yale University. His work with Mary Leakey's team at Laeotoli, Tanzania, in the 1970s helped lead to the discovery of the fossilized footprints of early hominids and other mammals. His current research interests include hominid evolution, paleoecology, and taphonomy.
HIV: Human Immunodeficiency Virus. The virus causes AIDS by inactivating the Tcells of the immune system.
homeobox: Homeoboxes are relatively short (approximately 180 base pair)sequences of DNA, characteristic of some homeotic genes (which play a central role in controlling body development). Homeoboxes code for a protein "homeodomain," a protein domain that binds to DNA, and can regulate the expression of other genes. These homeodomain motifs are involved in orchestrating the development of a wide range of organisms.
homeobox genes: "Homeobox genes" are genes that contain "homeoboxes", and can regulate the expression of other genes. There are at least 24 homeobox genes, some but not all of which are also homeotic in their effect. In general, “homeotic" genes are genes that control the identity of body parts. They are active in the early stages of embryonic development of organisms. Some, but not all, homeotic genes are homeobox genes. "Hox" genes are a subgroup of homeotichomeobox genes that determine positional cell differentiation and development. They lay out the head to tail body pattern in very early embryos. The Hox gene sare very ancient and widely shared among bilateral animals. After the head to tail pattern is established, homeotic genes direct the developmental fates of particular groups of cells.
homeostasis (developmental): A self-regulating process in development, such that the organism grows up to have much the same form independent of the external influences it experiences while growing up.
homeotic mutation: A mutation causing one structure of an organism to grow in the place appropriate to another. For example, in the mutation called "antennapedia" in the fruit fly, a foot grows in the antennal socket.
hominids: Members of the family Hominidae, which includes only modern humans and their ancestors since the human lineage split from the apes.
homogametic: The sex with two of the same kind of chromosomes (females in mammals, because they are XX). Compare with heterogametic.
homologous structures: The structures shared by a set of related species because they have been inherited, with or without modification, from their common ancestor. For example, the bones that support a bat's wing are similar to those of a human arm.
homology: A character shared by a set of species and present in their common ancestor. Compare with analogy. (Some molecular biologists, when comparing two sequences, call the corresponding sites "homologous" if they have the same nucleotide, regardless of whether the similarity is evolutionarily shared from a common ancestor or convergent. They likewise talk about percent homology between the two sequences. Homology in this context simply means similarity. This usage is frowned upon by many evolutionary biologists, but is established in much of the molecular literature.)
homozygote: An individual having two copies of the same allele at a genetic locus. Also sometimes applied to larger genetic entities, such as a whole chromosome; a homozygote is then an individual having two copies of the same chromosome.
homozygous: Having identical alleles for a particular trait. See also homozygote.
Homo erectus: A species of hominid that lived between 1.8 mya and 300,000 years ago; the first Homo species to migrate beyond Africa.
Homo habilis: A species of hominid that lived between 1.9 and 1.8 mya, the first species in genus Homo, and the first hominid associated with clear evidence of tool manufacture and use.
Homo neanderthalensis: A species of hominid that lived between 150,000 and30,000 years ago in Europe and Western Asia, originally thought to be a geographic variant of Homo sapiens but now generally accepted to be a distinct species.
Homo sapiens: Modern humans, which evolved to their present form about 100,000years ago.
horsetail: A seedless plant related to ferns. Twenty-five species of only one genus, Equisteum, remain today, whereas many different species, some the size of modern trees, were abundant in ancient swamps. Along with lycophytes and ferns, horsetails were among the first terrestrial plants to appear.
Ho, David: A physician and world-renowed AIDS researcher. Dr. Ho overturned an earlier conventional assumption that the HIV virus remains dormant for up to 10 years in a person before its outbreak into AIDS. His recognition that the virus is active right from the beginning of infection led him to initiate the deployment of a combination of drugs to overpower the virus.hox genes: A particular subgroup of homeobox genes that function to pattern the axis of an organism Õs body and determine where limbs and other body segments will grow as the embryo develops.
Huxley, Thomas Henry: British intellect, photographer, and contemporary of Darwin. He was the first to apply the theory of natural selection to humanity to explain the course of human evolution.
hybrid: The offspring of a cross between two species.
hypothesis: An explanation of one or more phenomena in nature that can be tested by observations, experiments, or both. In order to be considered scientific, a hypothesis must be falsifiable, which means that it can be proven to be incorrect.
Haile Selassie, Yohannes: A paleoanthropologist who, while doing field work in Ethiopia for his doctoral dissertation at the University of California, Berkeley, discovered Ardipithecus ramidus kadabba, a bipedal hominid dated at5.2 million years old.
half-life: The amount of time it takes for one-half of the atoms of a radioactive material to decay to a stable form. For example, the half-life ofcarbon-14 is 5,568 years.
Hamilton, W.D.: A naturalist, explorer, and zoologist who worked in the world of mathematical models, including "Hamilton's Rule," about the spread through a population of a gene for altruistic self sacrifice. He was also interested in the evolutionary impact of parasites as the key to many outstanding problemsl eft by Darwin, including the baffling riddle of the evolution of sex. This led him to extensive work in computer simulations.
haploid: The condition of having only one set of genes or chromosomes. In normally diploid organisms such as humans, only the gametes are haploid.
haplotype: A set of genes at more than one locus inherited by an individual from one of its parents. It is the multi-locus analog of an allele.
Hardy-Weinberg principle: In population genetics, the idea that if a population experienced no selection, no mutation, no migration, no genetic drift, and random mating, then the frequency of each allele and the frequencies of genotype in the population would remain the same from one generation to the next.
Hardy-Weinberg ratio: The ratio of genotype frequencies that evolve when mating is random and neither selection nor drift are operating. For two alleles (A and a) with frequencies p and q, there are three genotypes: AA, Aa, and aa. The Hardy-Weinberg ratio for the three is: p2AA : 2pqAa : q2aa. It is the starting point for much of the theory of population genetics.
Harvey, Ralph: A geologist whose work includes the study of geological processes at a range of scales, from the smallest nanometer to broader-scale interpretations of the history experienced by geological materials.
heavy metals: Metals with a high relative atomic mass, such as lead, copper, zinc, and mercury. Many of them are toxic.
hemoglobin: A protein that carries oxygen from the lungs throughout the body.
heredity: The process by which characteristics are passed from one generation to the next.
heritability: Broadly, the proportion of variation (more strictly, variance) in a phenotypic character in a population that is due to individual differences in genotypes. Narrowly, it is defined as the proportion of variation (more strictly, variance) in a phenotypic character in a population that is due to individual genetic differences that will be inherited in the offspring.
heritable: Partly or wholly determined by genes; capable of being passed from an individual to its offspring.
Herrnstein, Richard J.: A professor of psychology and an author of notable books on intelligence and crime. He has primarily done research on human and animal motivational and learning processes. His books include Psychology and I. Q. in the Meritocracy, and he coauthored (with Charles Murray) The Bell Curve: Intelligence and Class Structure in American Life (1994).
heterogametic: The sex with two different sex chromosomes (males in mammals ,because they are XY). Compare with homogametic.
heterozygosity: (for most purposes) The proportion of individuals in a population that are heterozygotes.
heterozygote: An individual having two different alleles at a genetic locus. Compare with homozygote.
heterozygote advantage: A condition in which the fitness of a heterozygote is higher than the fitness of either homozygote.
heterozygous: Having two different alleles for a particular trait. See also heterozygote.
Hill, Andrew: A paleontologist and professor at Yale University. His work with Mary Leakey's team at Laeotoli, Tanzania, in the 1970s helped lead to the discovery of the fossilized footprints of early hominids and other mammals. His current research interests include hominid evolution, paleoecology, and taphonomy.
HIV: Human Immunodeficiency Virus. The virus causes AIDS by inactivating the Tcells of the immune system.
homeobox: Homeoboxes are relatively short (approximately 180 base pair)sequences of DNA, characteristic of some homeotic genes (which play a central role in controlling body development). Homeoboxes code for a protein "homeodomain," a protein domain that binds to DNA, and can regulate the expression of other genes. These homeodomain motifs are involved in orchestrating the development of a wide range of organisms.
homeobox genes: "Homeobox genes" are genes that contain "homeoboxes", and can regulate the expression of other genes. There are at least 24 homeobox genes, some but not all of which are also homeotic in their effect. In general, “homeotic" genes are genes that control the identity of body parts. They are active in the early stages of embryonic development of organisms. Some, but not all, homeotic genes are homeobox genes. "Hox" genes are a subgroup of homeotichomeobox genes that determine positional cell differentiation and development. They lay out the head to tail body pattern in very early embryos. The Hox gene sare very ancient and widely shared among bilateral animals. After the head to tail pattern is established, homeotic genes direct the developmental fates of particular groups of cells.
homeostasis (developmental): A self-regulating process in development, such that the organism grows up to have much the same form independent of the external influences it experiences while growing up.
homeotic mutation: A mutation causing one structure of an organism to grow in the place appropriate to another. For example, in the mutation called "antennapedia" in the fruit fly, a foot grows in the antennal socket.
hominids: Members of the family Hominidae, which includes only modern humans and their ancestors since the human lineage split from the apes.
homogametic: The sex with two of the same kind of chromosomes (females in mammals, because they are XX). Compare with heterogametic.
homologous structures: The structures shared by a set of related species because they have been inherited, with or without modification, from their common ancestor. For example, the bones that support a bat's wing are similar to those of a human arm.
homology: A character shared by a set of species and present in their common ancestor. Compare with analogy. (Some molecular biologists, when comparing two sequences, call the corresponding sites "homologous" if they have the same nucleotide, regardless of whether the similarity is evolutionarily shared from a common ancestor or convergent. They likewise talk about percent homology between the two sequences. Homology in this context simply means similarity. This usage is frowned upon by many evolutionary biologists, but is established in much of the molecular literature.)
homozygote: An individual having two copies of the same allele at a genetic locus. Also sometimes applied to larger genetic entities, such as a whole chromosome; a homozygote is then an individual having two copies of the same chromosome.
homozygous: Having identical alleles for a particular trait. See also homozygote.
Homo erectus: A species of hominid that lived between 1.8 mya and 300,000 years ago; the first Homo species to migrate beyond Africa.
Homo habilis: A species of hominid that lived between 1.9 and 1.8 mya, the first species in genus Homo, and the first hominid associated with clear evidence of tool manufacture and use.
Homo neanderthalensis: A species of hominid that lived between 150,000 and30,000 years ago in Europe and Western Asia, originally thought to be a geographic variant of Homo sapiens but now generally accepted to be a distinct species.
Homo sapiens: Modern humans, which evolved to their present form about 100,000years ago.
horsetail: A seedless plant related to ferns. Twenty-five species of only one genus, Equisteum, remain today, whereas many different species, some the size of modern trees, were abundant in ancient swamps. Along with lycophytes and ferns, horsetails were among the first terrestrial plants to appear.
Ho, David: A physician and world-renowed AIDS researcher. Dr. Ho overturned an earlier conventional assumption that the HIV virus remains dormant for up to 10 years in a person before its outbreak into AIDS. His recognition that the virus is active right from the beginning of infection led him to initiate the deployment of a combination of drugs to overpower the virus.hox genes: A particular subgroup of homeobox genes that function to pattern the axis of an organism Õs body and determine where limbs and other body segments will grow as the embryo develops.
Huxley, Thomas Henry: British intellect, photographer, and contemporary of Darwin. He was the first to apply the theory of natural selection to humanity to explain the course of human evolution.
hybrid: The offspring of a cross between two species.
hypothesis: An explanation of one or more phenomena in nature that can be tested by observations, experiments, or both. In order to be considered scientific, a hypothesis must be falsifiable, which means that it can be proven to be incorrect.
Dictionary of Evolutionary Nomenclature - Letter G
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.
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.
Dictionary of Evolutionary Nomenclature - Letter F
fact: A natural phenomenon repeatedly confirmed by observation.
family: The category of taxonomic classification between order and genus (see taxon). Organisms within a family share a close similarity; for example, the catfamily, Felidae, which includes lions and domestic cats.
fauna: Animal life; often used to distinguish from plant life ("flora").
fermentation: A series of reactions occurring under anaerobic conditions(lacking oxygen) in certain microorganisms (particularly yeasts) in which organic compounds such as glucose are converted into simpler substances with the release of energy. Fermentation is involved in bread making, where the carbon dioxide produced by the yeast causes dough to rise.
fetus: The embryo of a mammal that has reached a stage of development in the uterus in which most of the adult features are recognizable. Specifically in humans it refers to the stage of development after the appearance of bone cells, a process occurring 7 to 8 weeks after fertilization.
fitness: The success of an individual (or allele or genotype in a population) in surviving and reproducing, measured by that individual's (or allele's orgenotype's) genetic contribution to the next generation and subsequent generations.
FitzRoy, Robert: Captain of the Beagle, which took Charles Darwin on his famousvoyage to South America and around the world. FitzRoy's chief mission on the Beagle was to chart the coast of South America. He also established the first weather warning system while on his journeys, with the help of the telegraph, and later rose to the rank of Admiral in the British Navy. He was known as a young man for his moody temperament, and in his older age for questionable sanity; FitzRoy's life ended in suicide.
fixation: A gene has achieved fixation when its frequency has reached 100 percent in the population.
fixed: (1) In population genetics, a gene is "fixed" when it has a frequency of 100 percent. (2) In creationism, species are described as "fixed" in the sense that they are believed not to change their form, or appearance, through time.
Flammer, Larry: A retired high school biology teacher and co-founder of the Santa Clara County Biotechnology-Education Partnership, which provides teacher training and lab equipment for local schools. He is a current member and Webwriter for the Evolution and Nature of Science Institute (ENSI).
flora: Plant life; often used to distinguish from animal life ("fauna").
foraminifera: These invertebrates are very common in the global ocean, and their distinctive, chambered shells are common in the fossil record as far back as 550million years. Although very few today exceed 9 mm in diameter, fossils have been found that measure 15 cm across.
fossil: Most commonly, an organism, a physical part of an organism, or an imprint of an organism that has been preserved from ancient times in rock, amber, or by some other means. New techniques have also revealed the existence of cellular and molecular fossils.
founder effect: The loss of genetic variation when a new colony is formed by a very small number of individuals from a larger population.
frequency-dependent selection: Selection in which the fitness of a genotype (or phenotype) depends on its frequency in the population.
fungi: A group of organisms comprising the kingdom Fungi, which includes molds and mushrooms. They can exist either as single cells or make up a multicellular body called a mycelium. Fungi lack chlorophyll and secrete digestive enzymes that decompose other biological tissues.
family: The category of taxonomic classification between order and genus (see taxon). Organisms within a family share a close similarity; for example, the catfamily, Felidae, which includes lions and domestic cats.
fauna: Animal life; often used to distinguish from plant life ("flora").
fermentation: A series of reactions occurring under anaerobic conditions(lacking oxygen) in certain microorganisms (particularly yeasts) in which organic compounds such as glucose are converted into simpler substances with the release of energy. Fermentation is involved in bread making, where the carbon dioxide produced by the yeast causes dough to rise.
fetus: The embryo of a mammal that has reached a stage of development in the uterus in which most of the adult features are recognizable. Specifically in humans it refers to the stage of development after the appearance of bone cells, a process occurring 7 to 8 weeks after fertilization.
fitness: The success of an individual (or allele or genotype in a population) in surviving and reproducing, measured by that individual's (or allele's orgenotype's) genetic contribution to the next generation and subsequent generations.
FitzRoy, Robert: Captain of the Beagle, which took Charles Darwin on his famousvoyage to South America and around the world. FitzRoy's chief mission on the Beagle was to chart the coast of South America. He also established the first weather warning system while on his journeys, with the help of the telegraph, and later rose to the rank of Admiral in the British Navy. He was known as a young man for his moody temperament, and in his older age for questionable sanity; FitzRoy's life ended in suicide.
fixation: A gene has achieved fixation when its frequency has reached 100 percent in the population.
fixed: (1) In population genetics, a gene is "fixed" when it has a frequency of 100 percent. (2) In creationism, species are described as "fixed" in the sense that they are believed not to change their form, or appearance, through time.
Flammer, Larry: A retired high school biology teacher and co-founder of the Santa Clara County Biotechnology-Education Partnership, which provides teacher training and lab equipment for local schools. He is a current member and Webwriter for the Evolution and Nature of Science Institute (ENSI).
flora: Plant life; often used to distinguish from animal life ("fauna").
foraminifera: These invertebrates are very common in the global ocean, and their distinctive, chambered shells are common in the fossil record as far back as 550million years. Although very few today exceed 9 mm in diameter, fossils have been found that measure 15 cm across.
fossil: Most commonly, an organism, a physical part of an organism, or an imprint of an organism that has been preserved from ancient times in rock, amber, or by some other means. New techniques have also revealed the existence of cellular and molecular fossils.
founder effect: The loss of genetic variation when a new colony is formed by a very small number of individuals from a larger population.
frequency-dependent selection: Selection in which the fitness of a genotype (or phenotype) depends on its frequency in the population.
fungi: A group of organisms comprising the kingdom Fungi, which includes molds and mushrooms. They can exist either as single cells or make up a multicellular body called a mycelium. Fungi lack chlorophyll and secrete digestive enzymes that decompose other biological tissues.
Dictionary of Evolutionary Nomenclature - Letter E
echinoderm: Echinoderms, whose name means "spiny skin," are a group of marine invertebrates that includes starfish, brittle stars, basket stars, sea cucumbers, sand dollars, sea urchins, and others. They live in environments from shallow coastal waters to deep-sea trenches, from the tropics to the poles.
ecological genetics: The study of evolution in action in nature, by a combination of field work and laboratory genetics.
ecological species concept: A concept of species, according to which a species is a set of organisms adapted to a particular, discrete set of resources (or "niche") in the environment. Compare with biological species concept, cladistic species concept, phenetic species concept, and recognition species concept.
ecosystem: A community of organisms interacting with a particular environment.
Eldredge, Niles: A paleontologist and evolutionary biologist with the American Museum of Natural History, Eldredge, together with Stephen Jay Gould, proposed the theory of punctuated equilibria, providing paleontologists with an explanation for the patterns which they find in the fossil record. He has written several books for a general audience, including Time Frames: The Evolution of Punctuated Equilibria and Life in the Balance: Humanity and the Biodiversity Crisis.
electrophoresis: The method of distinguishing entities according to their motility in an electric field. In evolutionary biology, it has been mainly used to distinguish different forms of proteins. The electrophoretic motility of a molecule is influenced by its size and electric charge.
embryo: An early stage of animal development that begins after division of the zygote (the earliest stage, in which joined egg and sperm have not yet divided).embryonic: Related to an embryo, or being in the state of an embryo.
embryology: scientific study of the earliest stages of growth and development inorganisms.
emigration: The movement of organisms out of an area.
Emlen, Stephen: A world authority on the social behavior of animals, particularly birds. Emlen's interests center on evolutionary or adaptive aspects of animal behavior. The goal of his research is to better understand the social interactions that occur between individuals, especially cooperation and conflict.
empirical: Determined by experimentation.
Endler, John: A zoologist and professor with interests in evolution and how it affects geographic variation. His current research focuses on guppies (Poeciliareticulata) in their natural habitat, and how visual signs and vision dictate their behavior.
enzyme: A protein that acts as a catalyst for chemical reactions.
Eocene: The second oldest of the five major epochs of the Tertiary period, from54 to 38 mya. It is often known for the rise of mammals.
epistasis: An interaction between the genes at two or more loci, such that the phenotype differs from at would be expected if the loci were expressed independently.
Erwin, Douglas: Dr. Erwin is a paleobiologist with the National Museum of Natural History in the Smithsonian Institution. His research is concerned with aspects of major evolutionary novelties, particularly the Metazoan radiation and post-mass extinction recoveries. Recent work has involved the developmental events associated with the Cambrian along with their environmental context. He also works on the rate, causes, and consequences of the end-Permian mass extinction.
eugenics: The science or practice of altering a population, especially of humans, by controlled breeding for desirable inherited characteristics. The term was coined in 1883 by Francis Galton, who was an advocate of "improving" the human race by modifying the fertility of different categories of people .Eugenics fell into disfavor after the perversion of its doctrines by the Nazis.
eukaryote: Any organism made up of eukaryotic cells. Eukaryotes are generally larger and have more DNA than prokaryotes (whose cells do not have a nucleus to contain their DNA). Almost all multicellular organisms are eukaryotes.
eukaryotic cell: A cell with a distinct nucleus.e
vo-devo: the informal name for 'evolutionary developmental biology', a branch of evolutionary studies that seeks to contribute insights from genetics, embryology and microbiology to help scientists better understand how new species arise from existing life forms
evolution: Darwin defined this term as "descent with modification." It is the change in a lineage of populations between generations. In general terms, biological evolution is the process of change by which new species develop from preexisting species over time; in genetic terms, evolution can be defined as any change in the frequency of alleles in populations of organisms from generation to generation.
evolutionary classification: Method of classification using both cladistic and phenetic classificatory principles. To be exact, it permits paraphyletic groups(which are allowed in phenetic but not in cladistic classification) and monophyletic groups (which are allowed in both cladistic and phonetic classification) but excludes polyphyletic groups (which are banned from cladistic classification but permitted in phenetic classification).
Ewald, Paul: Professor of biology at Amherst College, specializing in hummingbird and flower coevolution and the evolution of infectious diseases. His research on disease focuses on the evolutionary effects of various public health interventions.
exon: The nucleotide sequences of some genes consist of parts that code foramino acids, with other parts that do not code for amino acids interspersed among them. The coding parts, which are translated, are called exons; the interspersed non-coding parts are called introns.
extinction: The disappearance of a species or a population.
ecological genetics: The study of evolution in action in nature, by a combination of field work and laboratory genetics.
ecological species concept: A concept of species, according to which a species is a set of organisms adapted to a particular, discrete set of resources (or "niche") in the environment. Compare with biological species concept, cladistic species concept, phenetic species concept, and recognition species concept.
ecosystem: A community of organisms interacting with a particular environment.
Eldredge, Niles: A paleontologist and evolutionary biologist with the American Museum of Natural History, Eldredge, together with Stephen Jay Gould, proposed the theory of punctuated equilibria, providing paleontologists with an explanation for the patterns which they find in the fossil record. He has written several books for a general audience, including Time Frames: The Evolution of Punctuated Equilibria and Life in the Balance: Humanity and the Biodiversity Crisis.
electrophoresis: The method of distinguishing entities according to their motility in an electric field. In evolutionary biology, it has been mainly used to distinguish different forms of proteins. The electrophoretic motility of a molecule is influenced by its size and electric charge.
embryo: An early stage of animal development that begins after division of the zygote (the earliest stage, in which joined egg and sperm have not yet divided).embryonic: Related to an embryo, or being in the state of an embryo.
embryology: scientific study of the earliest stages of growth and development inorganisms.
emigration: The movement of organisms out of an area.
Emlen, Stephen: A world authority on the social behavior of animals, particularly birds. Emlen's interests center on evolutionary or adaptive aspects of animal behavior. The goal of his research is to better understand the social interactions that occur between individuals, especially cooperation and conflict.
empirical: Determined by experimentation.
Endler, John: A zoologist and professor with interests in evolution and how it affects geographic variation. His current research focuses on guppies (Poeciliareticulata) in their natural habitat, and how visual signs and vision dictate their behavior.
enzyme: A protein that acts as a catalyst for chemical reactions.
Eocene: The second oldest of the five major epochs of the Tertiary period, from54 to 38 mya. It is often known for the rise of mammals.
epistasis: An interaction between the genes at two or more loci, such that the phenotype differs from at would be expected if the loci were expressed independently.
Erwin, Douglas: Dr. Erwin is a paleobiologist with the National Museum of Natural History in the Smithsonian Institution. His research is concerned with aspects of major evolutionary novelties, particularly the Metazoan radiation and post-mass extinction recoveries. Recent work has involved the developmental events associated with the Cambrian along with their environmental context. He also works on the rate, causes, and consequences of the end-Permian mass extinction.
eugenics: The science or practice of altering a population, especially of humans, by controlled breeding for desirable inherited characteristics. The term was coined in 1883 by Francis Galton, who was an advocate of "improving" the human race by modifying the fertility of different categories of people .Eugenics fell into disfavor after the perversion of its doctrines by the Nazis.
eukaryote: Any organism made up of eukaryotic cells. Eukaryotes are generally larger and have more DNA than prokaryotes (whose cells do not have a nucleus to contain their DNA). Almost all multicellular organisms are eukaryotes.
eukaryotic cell: A cell with a distinct nucleus.e
vo-devo: the informal name for 'evolutionary developmental biology', a branch of evolutionary studies that seeks to contribute insights from genetics, embryology and microbiology to help scientists better understand how new species arise from existing life forms
evolution: Darwin defined this term as "descent with modification." It is the change in a lineage of populations between generations. In general terms, biological evolution is the process of change by which new species develop from preexisting species over time; in genetic terms, evolution can be defined as any change in the frequency of alleles in populations of organisms from generation to generation.
evolutionary classification: Method of classification using both cladistic and phenetic classificatory principles. To be exact, it permits paraphyletic groups(which are allowed in phenetic but not in cladistic classification) and monophyletic groups (which are allowed in both cladistic and phonetic classification) but excludes polyphyletic groups (which are banned from cladistic classification but permitted in phenetic classification).
Ewald, Paul: Professor of biology at Amherst College, specializing in hummingbird and flower coevolution and the evolution of infectious diseases. His research on disease focuses on the evolutionary effects of various public health interventions.
exon: The nucleotide sequences of some genes consist of parts that code foramino acids, with other parts that do not code for amino acids interspersed among them. The coding parts, which are translated, are called exons; the interspersed non-coding parts are called introns.
extinction: The disappearance of a species or a population.
Dictionary of Evolutionary Nomenclature - Letter D
Daeschler, Ted: Paleontologist and associate research curator at the Academy of Natural Sciences. Discoverer of late Devonian limbed fossils Hynerpeton bassetti and Designathus rowei (tetrapods) and Sauripterus taylorii and Hyneria (lobed-finned fishes), all early examples of animals exploiting both land and water environments. Author of two books on paleontology for young people.
Dart, Raymond: Australian-born South African anatomist and anthropologist(1893-1988). In 1924 he described a fossil skull collected near Taung in South Africa, naming it Australopithecus africanus. Dart asserted that the skull was intermediate between the apes and humans, a controversial claim at the time, though later work made it clear that the Taung child, as it came to be known, was indeed a hominid.
Darwinian evolution: Evolution by the process of natural selection acting on random variation.
Darwinism: Darwin's theory that species originated by evolution from other species and that evolution is mainly driven by natural selection. Differs from neo-Darwinism mainly in that Darwin did not know about Mendelian inheritance.
Darwin, Charles: The 19th-century naturalist considered the father of evolution. His landmark work, On the Origin of Species, published in 1859, presented a wealth of facts supporting the idea of evolution and proposed a viable theory for how evolution occurs -- via the mechanism Darwin called "natural selection."In addition to his prolific work in biology, Darwin also published important works on coral reefs and on the geology of the Andes, and a popular travelogue of his five-year voyage aboard HMS Beagle.
Darwin, Erasmus: The name shared by Charles Darwin's grandfather and brother, each important in his life and work. Charles's grandfather Erasmus (1731-1802)was a glorious polymath -- physician, author, and botanist. His impact is reflected throughout a wide range of disciplines from the poetry to the technology of his day. Author of The Loves of the Plants, a 2,000-line poem detailing their sexual reproduction, and Zoonomia, or the Theory of Generations, whose themes echo throughout his grandson's work. Charles's older brother Erasmus (1805-1881), known as "Ras," used his network of social and scientific contacts to advance the theories of his shyer, more retiring sibling.
Dawkins, Richard: An evolutionary biologist who has taught zoology and is the author of several books on evolution and science, including The Selfish Gene(1976) and The Blind Watchmaker (1986). He is known for his popularization of Darwinian ideas, as well as for original thinking on evolutionary theory.
Dembski, William: A mathematician and philosopher who has written on intelligent design, attempting to establish the legitimacy and fruitfulness of design withinbiology.
Dennett, Daniel: Philosopher and director of the Center for Cognitive Studies at Tufts University, whose work unites neuroscience, computer science, and evolutionary biology. Dennett sees no basic distinction between human and machine intelligence, advocating a mechanical explanation of consciousness. He is the author of Brainchildren: Essays on Designing Minds and Darwin's Dangerous Idea: Evolution and the Meanings of Life, among many other books and publications.
derived homology: Homology that first evolved in the common ancestor of a set of species and is unique to those species. Compare with ancestral homology.
de facto: In fact; in reality. Something which exists or occurs de facto is not the result of a law, but because of circumstances.
diatom: These single-celled algae are common among the marine phytoplankton. Their glassy, two-part shells have intricate patterns and fit together like the two parts of a shirt box.
diffusion: The process by which molecules (for example, of oxygen) move passively from a region of high concentration to a region of low concentration.
dinoflagellate: Possessing two tail-like extensions called flagella that are used for movement, these single-celled algae can live freely or in other organisms such as corals. When many dinoflagellates suddenly reproduce in great numbers, they create what are known as "red tides" by making the water appearred.
diploid: Having two sets of genes and two sets of chromosomes (one from the mother, one from the father). Many common species, including humans, are diploid. Compare with haploid and polyploid.
directional selection: Selection causing a consistent directional change in the form of a population through time (e.g., selection for larger body size).disruptive selection: Selection favoring forms that deviate in either direction from the population average. Selection favors forms that are larger or smaller than average, but works against the average forms between the extremes.
distance: In taxonomy, referring to the quantitatively measured difference between the phenetic appearance of two groups of individuals, such as populations or species (phenetic distance), or the difference in their gene frequencies (genetic distance).
DNA: Deoxyribonucleic acid, the molecule that controls inheritance.DNA base sequence: A chain of repeating units of deoxyribonucleotides (adenine, guanine, cytosice, thymine) arranged in a particular pattern.
Dobzhansky, Theodosius: A geneticist and zoologist best known for his research in population genetics using the fruit fly. His study of the evolution of races led to the discovery of genetic diversity within species, and confirmed his belief that genetic variation leads to better adaptability.
dominance (genetic): An allele (A) is dominant if the phenotype of the heterozygote (Aa) is the same as the homozygote (AA). The allele (a) does not influence the heterozygote's phenotype and is called recessive. An allele may be partly, rather than fully, dominant; in that case, the heterozygous phenotype is nearer to, rather than identical with, the homozygote of the dominant allele.
drift: Synonym of genetic drift.
duplication: The occurrence of a second copy of a particular sequence of DNA. The duplicate sequence may appear next to the original or be copied elsewhere into the genome. When the duplicated sequence is a gene, the event is called gene duplication.
Dart, Raymond: Australian-born South African anatomist and anthropologist(1893-1988). In 1924 he described a fossil skull collected near Taung in South Africa, naming it Australopithecus africanus. Dart asserted that the skull was intermediate between the apes and humans, a controversial claim at the time, though later work made it clear that the Taung child, as it came to be known, was indeed a hominid.
Darwinian evolution: Evolution by the process of natural selection acting on random variation.
Darwinism: Darwin's theory that species originated by evolution from other species and that evolution is mainly driven by natural selection. Differs from neo-Darwinism mainly in that Darwin did not know about Mendelian inheritance.
Darwin, Charles: The 19th-century naturalist considered the father of evolution. His landmark work, On the Origin of Species, published in 1859, presented a wealth of facts supporting the idea of evolution and proposed a viable theory for how evolution occurs -- via the mechanism Darwin called "natural selection."In addition to his prolific work in biology, Darwin also published important works on coral reefs and on the geology of the Andes, and a popular travelogue of his five-year voyage aboard HMS Beagle.
Darwin, Erasmus: The name shared by Charles Darwin's grandfather and brother, each important in his life and work. Charles's grandfather Erasmus (1731-1802)was a glorious polymath -- physician, author, and botanist. His impact is reflected throughout a wide range of disciplines from the poetry to the technology of his day. Author of The Loves of the Plants, a 2,000-line poem detailing their sexual reproduction, and Zoonomia, or the Theory of Generations, whose themes echo throughout his grandson's work. Charles's older brother Erasmus (1805-1881), known as "Ras," used his network of social and scientific contacts to advance the theories of his shyer, more retiring sibling.
Dawkins, Richard: An evolutionary biologist who has taught zoology and is the author of several books on evolution and science, including The Selfish Gene(1976) and The Blind Watchmaker (1986). He is known for his popularization of Darwinian ideas, as well as for original thinking on evolutionary theory.
Dembski, William: A mathematician and philosopher who has written on intelligent design, attempting to establish the legitimacy and fruitfulness of design withinbiology.
Dennett, Daniel: Philosopher and director of the Center for Cognitive Studies at Tufts University, whose work unites neuroscience, computer science, and evolutionary biology. Dennett sees no basic distinction between human and machine intelligence, advocating a mechanical explanation of consciousness. He is the author of Brainchildren: Essays on Designing Minds and Darwin's Dangerous Idea: Evolution and the Meanings of Life, among many other books and publications.
derived homology: Homology that first evolved in the common ancestor of a set of species and is unique to those species. Compare with ancestral homology.
de facto: In fact; in reality. Something which exists or occurs de facto is not the result of a law, but because of circumstances.
diatom: These single-celled algae are common among the marine phytoplankton. Their glassy, two-part shells have intricate patterns and fit together like the two parts of a shirt box.
diffusion: The process by which molecules (for example, of oxygen) move passively from a region of high concentration to a region of low concentration.
dinoflagellate: Possessing two tail-like extensions called flagella that are used for movement, these single-celled algae can live freely or in other organisms such as corals. When many dinoflagellates suddenly reproduce in great numbers, they create what are known as "red tides" by making the water appearred.
diploid: Having two sets of genes and two sets of chromosomes (one from the mother, one from the father). Many common species, including humans, are diploid. Compare with haploid and polyploid.
directional selection: Selection causing a consistent directional change in the form of a population through time (e.g., selection for larger body size).disruptive selection: Selection favoring forms that deviate in either direction from the population average. Selection favors forms that are larger or smaller than average, but works against the average forms between the extremes.
distance: In taxonomy, referring to the quantitatively measured difference between the phenetic appearance of two groups of individuals, such as populations or species (phenetic distance), or the difference in their gene frequencies (genetic distance).
DNA: Deoxyribonucleic acid, the molecule that controls inheritance.DNA base sequence: A chain of repeating units of deoxyribonucleotides (adenine, guanine, cytosice, thymine) arranged in a particular pattern.
Dobzhansky, Theodosius: A geneticist and zoologist best known for his research in population genetics using the fruit fly. His study of the evolution of races led to the discovery of genetic diversity within species, and confirmed his belief that genetic variation leads to better adaptability.
dominance (genetic): An allele (A) is dominant if the phenotype of the heterozygote (Aa) is the same as the homozygote (AA). The allele (a) does not influence the heterozygote's phenotype and is called recessive. An allele may be partly, rather than fully, dominant; in that case, the heterozygous phenotype is nearer to, rather than identical with, the homozygote of the dominant allele.
drift: Synonym of genetic drift.
duplication: The occurrence of a second copy of a particular sequence of DNA. The duplicate sequence may appear next to the original or be copied elsewhere into the genome. When the duplicated sequence is a gene, the event is called gene duplication.
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