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17 terms

Ch 12 History of Life on Earth

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Radiometric dating
a method of determining the age of an object by estimating the relative percentages of a radioactive (parent) isotope and a stable (daughter) isotope.
radioisotope
unstable isotopes that break down and give off energy in the form of charged particles (radiation)
half-life
the time required for half of a sample of a radioactive substance to disintigrate by radioactive decay or by natural processes
microsphere
Short chains of amino acids that gather into tiny droplets in water
fossil
the trace or remains of an organism that lived long ago, preserved in sedimentary rock
cyanobacteria
a bacterium that can carry out photosynthesis, such as a blue-green alga
eubacteria
a classification kingdom that contains all prokaryotes except archaebacteria
archaebacteria
a classification kingdom made up of bacteria that live in extreme environments; differentiated from other prokaryotes by various important chemical differences
endosymbiosis
a mutually beneficial relationship in which one organism lives within another
protist
an organism that belongs to the kingdom protista
extinction (extinct)
describes a species of organisms that has died out completely
mass extinction
an episode during which large numbers of species become extinct
mycorrhizae
a symbiotic associations between fungi and plant roots
mutualism
a relationship between two species in which both species benefit
arthropod
a member of the phylum Arthropoda, which includes invertebrate animals such as insects, crustaceans, and arachnids; characterized by having segmented bodies and paired appendages
vertebrate
an animal that has a backbone; includes mammals, birds, reptiles, amphibians, and fish
continental drift
the hypothesis that states that the continents once formed a single landmass, broke up, and drifted to their present locations