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.