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The History of Life

Science

anthropoid

human-like primates, including new world monkeys, old world monkeys, and hominoids
anthropoid Simple Definition

bipedal

walking on two legs, like a human, ostrich, or kangaroo
bipedal Simple Definition

cambrian explosion

a rapid increase in the diversity of lifeforms that occurred during the Paleozoic era
cambrian explosion Simple Definition

endosymbiotic theory

states that mitochondria and chloroplasts evolved from eukaryotic cells that entered prokaryotic cells
endosymbiotic theory Simple Definition

epoch

a unit of geologic time longer than an age but shorter than a period
epoch Simple Definition

era

the second-longest unit of geologic time, it is divided into periods
era Simple Definition

geologic time scale

a timeline of Earth's history based on major changes
geologic time scale Simple Definition

half-life

the time it takes for half the atoms of a radioactive isotope to decay
half-life Simple Definition

index fossil

a fossil from an organism that existed for a short time, it is used to determine the age of other fossils
index fossil Simple Definition

mass extinction

when many species become extinct at the same time
mass extinction Simple Definition

paleontologist

a scientist who studies fossils
paleontologist Simple Definition

period

a unit of geologic time that lasts tens of millions of years, it is longer than an epoch but shorter than an era
period Simple Definition

plate tectonics

the theory that Earth's crust is made of moving plates
plate tectonics Simple Definition

primate

mammals with features like opposable thumbs, forward looking eyes, and a large brain, like humans, monkeys or apes
primate Simple Definition

radiometric dating

comparing the amount of radioactive and nonradioactive isotopes to determine rock age
radiometric dating Simple Definition

relative dating

a method of comparing fossils or rocks to determine which is older
relative dating Simple Definition

spontaneous generation

the theory that life can arise from nonliving things
spontaneous generation Simple Definition

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