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  • Any heritable characteristic of an organism that improves its ability to survive and reproduce in its environment. Also used to describe the process of genetic change within a population, as influenced by natural selection.

    A graph of the average fitness of a population in relation to the frequencies of genotypes in it. Peaks on the landscape correspond to genotypic frequencies at which the average fitness is high, valleys to genotypic frequencies at which the average fitness is low. Also called a fitness surface. A behavior has adaptive logic if it tends to increase the number of offspring that an individual contributes to the next and following generations.

    If such a behavior is even partly genetically determined, it will tend to become widespread in the population. Then, even if circumstances change such that it no longer provides any survival or reproductive advantage, the behavior will still tend to be exhibited -- unless it becomes positively disadvantageous in the new environment. The diversification, over evolutionary time, of a species or group of species into several different species or subspecies that are typically adapted to different ecological niches for example, Darwin's finches.

    The term can also be applied to larger groups of organisms, as in "the adaptive radiation of mammals. A mode of coping with competition or environmental conditions on an evolutionary time scale.

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    Species adapt when succeeding generations emphasize beneficial characteristics. A person who believes that the existence of a god or creator and the nature of the universe is unknowable. An umbrella term for various simple organisms that contain chlorophyll and can therefore carry out photosynthesis and live in aquatic habitats and in moist situations on land.

    The term has no direct taxonomic significance.

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    Algae range from macroscopic seaweeds such as giant kelp, which frequently exceeds 30 m in length, to microscopic filamentous and single-celled forms such as Spirogyra and Chlorella.

    One of the alternative forms of a gene. For example, if a gene determines the seed color of peas, one allele of that gene may produce green seeds and another allele produce yellow seeds. In a diploid cell there are usually two alleles of any one gene one from each parent.

    Within a population there may be many different alleles of a gene; each has a unique nucleotide sequence. The relation between the size of an organism and the size of any of its parts.

    For example, an allometric relation exists between brain size and body size, such that in this case animals with bigger bodies tend to have bigger brains. Allometric relations can be studied during the growth of a single organism, between different organisms within a species, or between organisms in different species.

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    Speciation that occurs when two or more populations of a species are geographically isolated from one another sufficiently that they do not interbreed. Living in separate places. The unit molecular building block of proteinswhich are chains of amino acids in a certain sequence. There are 20 main amino acids in the proteins of living things, and the properties of a protein are determined by its particular amino acid sequence. A series of amino acids, the building blocks of proteinsusually coded for by DNA.

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    Extinct relatives of cephalopods squid, octopi, and chambered nautilusesthese mollusks had coiled shells and are found in the fossil record of the Cretaceous period. The group of reptiles, birds, and mammals. These all develop through an embryo that is enclosed within a membrane called an amnion. The amnion surrounds the embryo with a watery substance, and is probably an adaptation for breeding on land.

    The class of vertebrates that contains the frogs, toads, newts, and salamanders. The amphibians evolved in the Devonian period about million years ago as the first vertebrates to occupy the land.

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    They have moist scaleless skin which is used to supplement the lungs in gas exchange. The eggs are soft and vulnerable to drying, therefore reproduction commonly occurs in water.

    Amphibian larvae are aquatic, and have gills for respiration; they undergo metamorphosis to the adult form. Most amphibians are found in damp environments and they occur on all continents except Antarctica. Structures in different species that look alike or perform similar functions e. Contrast with homologous structures. The recent discovery of deep genetic homologies has brought new interest, new information, and discussion to the classical concepts of analogous and homologous structures.

    Homology that evolved before the common ancestor of a set of speciesand which is present in other species outside that set of species. Compare with derived homology.

    A member of the group of primates made up of monkeys, apes, and humans. Having the ability to kill bacteria. Substances that destroy or inhibit the growth of microorganisms, particularly disease-causing bacteria.

    A heritable trait in microorganisms that enables them to survive in the presence of an antibiotic. Of a camera, the adjustable opening through which light passes to reach the film. The diameter of the aperture determines the intensity of light admitted. The pupil of a human eye is a self-adjusting aperture. The study of human history and prehistory through the excavation of sites and the analysis of physical remains, such as graves, tools, pottery, and other artifacts.

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    The original form or body plan from which a group of organisms develops. An object made by humans that has been preserved and can be studied to learn about a particular time period. The process by which humans breed animals and cultivate crops to ensure that future generations have specific desirable characteristics.

    In artificial selection, breeders select the most desirable variants in a plant or animal population and selectively breed them with other desirable individuals. The forms of most domesticated and agricultural species have been produced by artificial selection; it is also an important experimental technique for studying evolution.

    A type of reproduction involving only one parent that ususally produces genetically identical offspring. Asexual reproduction occurs without fertilization or genetic recombinationand may occur by budding, by division of a single cell, or by the breakup of a whole organism into two or more new individuals.

    The tendency of like to mate with like. Mating can be assortative for a certain genotype e.

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    A small rocky or metallic body orbitting the Sun. About 20, have been observed, ranging in size from several hundred kilometers across down to dust particles. The doctrine or belief that there is no god. Mendelian inheritance is an atomistic theory because in it, inheritance is controlled by distinct genes. A group of bipedal hominid species belonging to the genus Australopithecus that lived between 4.

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    An early australopithecine species that was bipedal ; known fossils date between 3. Any chromosome other than a sex chromosome.

    Of, relating to, or characteristic of birds members of the class Aves. Tiny, single-celled, prokaryotic organisms that can survive in a wide variety of environments.

    Some cause serious infectious diseases in humans, other animals, and plants. The DNA molecule is a chain of nucleotide units; each unit consists of a backbone made of a sugar and a phosphate group, with a nitrogenous base attached.

    The base in a unit is one of adenine Aguanine Gcytosine Cor thymine T. In RNA, uracil U is used instead of thymine. A and G belong to the chemical class called purines ; C, T, and U are pyrimidines. A kind of mimicry in which one non-poisonous species the Batesian mimic mimics another poisonous species.

    An extinct marine invertebrate that was related to squid, octopi, and chambered nautiluses. We know from the fossil record that belemnites were common in the Jurassic period and had bullet-shaped internal skeletons.

    The theory that states that the universe began in a state of compression to infinite density, and that in one instant all matter and energy began expanding and have continued expanding ever since. A measure of the variety of life, biodiversity is often described on three levels. Ecosystem diversity describes the variety of habitats present; species diversity is a measure of the number of species and the number of individuals of each species present; genetic diversity refers to the total amount of genetic variability present.

    Food that has been produced through genetic modification using techniques of genetic engineering. Name given by Haeckel to recapitulation. The study of patterns of geographical distribution of plants and animals across Earth, and the changes in those distributions over time. The concept of speciesaccording to which a species is a set of organisms that can interbreed among each other.

    Compare with cladistic species conceptecological species conceptphenetic species conceptand recognition species concept. The quantitative study of characters of organisms. The part of Earth and its atmosphere capable of sustaining life.

    Of hominidswalking upright on two hind legs; more generally, using two legs for locomotion. A mollusk that has a two-part hinged shell. Bivalves include clams, oysters, scallops, mussels, and other shellfish. A psychologist interested in memes and the theory of memetics, evolutionary theory, consciousness, the effects of meditation, and why people believe in the paranormal.

    A recent book, The Meme Machine, offers an introduction to the subject of memes. The historically influential but factually erroneous theory that organisms contain a blend of their parents' hereditary factors and pass that blend on to their offspring.

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    Compare with Mendelian inheritance. A scientist who studies plants. Commonly known as "lamp shells," these marine invertebrates resemble bivalve mollusks because of their hinged shells. Brachiopods were at their greatest abundance during the Paleozoic and Mesozoic eras. A biologist who studies the causes and evolutionary implications of interactions among traits in predators and their prey. Much of his work concentrates on the coevolutionary arms race between newts that posess tetrodotoxin, one of the most potent known toxins, and the resistant garter snakes who prey on them.

    A biologist recognized internationally for his work on the evolution of mechanisms in amphibians that allow them to avoid predators.

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