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Ch 14 ES Vocab
Term | Definition |
---|---|
Cenozoic Era | era of recent life that began about 66 million years ago and continues today; includes the first appearance of Homo sapiens about 400,000 years ago |
cyanobacteria | chlorophyll-containing, photosynthetic bacteria thought to be one of Earth's earliest life-forms |
eon | longest subdivision in the geologic time scale that is based on the abundance of certain types of fossils and is subdivided into eras, periods, and epochs |
epoch | next-smaller division of geologic time after the period; is characterized by differences in life-forms that may vary regionally |
era | second-longest division of geologic time; is subdivided into periods and is based on major worldwide changes in types of fossils |
geologic time | division of Earth's history into time units based largely on the types of life-forms that lived only during certain periods |
Mesozoic Era | middle era of Earth's history, during which Pangaea broke apart, dinosaurs appeared, and reptiles and gymnosperms were the dominant land life-forms |
natural selection | process by which organisms that are suited to a particular environment are better able to survive and reproduce than organisms that are not |
organic evolution | change of organisms over geologic time |
Paleozoic Era | era of ancient life, which began about 544 million years ago, when organisms developed hard parts, and ended with mass extinctions about 245 million years ago |
Pangaea | large ancient landmass that was composed of al the continents joined together |
period | third-longest division of geologic time; is subdivided into epochs and is characterized by the types of life that existed worldwide |
Precambrian time | longest part of Earth's history, lasting from 4.0 billion to about 544 million years ago |
species | group of organisms that reproduces only with other members of their own group |
trilobite | organism with a three-lobed exoskeleton that was abundant in Paleozoic oceans and is considered to be an index fossil |