Changes Over Time and Evolution

Science

cast

a fossil formed when dissolved minerals fill a mold and harden

cast Simple Definition

evolution

the change in a species over time

evolution Simple Definition

extinction

the death of all members of a species

extinction Simple Definition

fossil

the preserved traces and remains of an organism that lived long ago

fossil Simple Definition

fossil record

the history of life recorded by all the fossils we have collected

fossil record Simple Definition

gradualism

the evolution of a species, as a gradual change over time

gradualism Simple Definition

homologous structure

a similar structure in different species, like a whale fin, bat wing and your arm

homologous structure Simple Definition

mass extinction

when many species become extinct at the same time

mass extinction Simple Definition

mold

a rock fossil created when a buried organism dissolves

mold Simple Definition

natural selection

the individuals best suited to survive in an environment

natural selection Simple Definition

primate

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

primate Simple Definition

radioactive element

an unstable element that emits particles and energy as it changes into another element

radioactive element Simple Definition

speciation

the evolution of new species from an existing species

speciation Simple Definition

variation

any difference between members of the same species

variation Simple Definition

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