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Biology
Chapter 25
Term | Definition |
---|---|
Stromalites | the first single-celled organisms and the oldest known fossils; rocks formed by the accumulations of sedimentary layers on bacterial mats. |
oxygen revolution | from 2.7 to 2.3 billion years ago caused the extinction of many prokaryotic groups. |
endosymbiotic theory | proposes that mitochondria and plastids (chloroplats and related organelles) were formerly small prokaryotes living within larger host cells. |
endosymbiont | a cell that lives within a host cell. |
serial endosymbiosis | supposes that mitochondria evolved before plastids through a sequence of endosymbiotic events. |
the "snowball Earth hypothesis" | suggests that periods of extreme glaciation confined life to the equational region or deep sea vents from 750 to 580 million years ago. |
Ediacaran biota | an assemblage of larger and more diverse soft-bodied organisms that lived from 575 to 535 million years ago. |
Cambrian explosion | the sudden appearance of fossils resembling modern animal phyla in the Cambrian period (535 to 525 million years ago). |
Permian extinction | the boundary between the Paleozoic and Mesozoic eras 251 million years ago. |
Cretaceous mass extinction | 65.5 million years ago separates the Mesozoic from the Cenozoic; caused the extinction of the dinosaurs |
adaptive radiation | the evolution of diversely adapted species from a common ancestor. |
heterochrony | an evolutionary change in the rate or timing of developmental events |
paedmorphosis | the rate of reproductive development accelerates compared with somatic development. |
homeotic genes | determine such basic features as where wings and legs will develop on a bird or how a flower's parts are arranged. |
hox genes | a class of homeotic genes that provide posotional information during development. |
binomial | the two part scientific name of a species. |
epithet | unique for each species within the genus. |
taxon | the taxonomic unit at any level of hierarchy. |