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Chapter 12

The History of Life

relative dating estimates the time during which an organism lived by comparing the placement of fossils of that organism with the placement of fossils in other layers of rock
radiometric dating a technique that uses the natural decay rate of unstable isotopes found in materials in order to calculate the age of that material
isotope atoms of an element that have the same number of protons but a different number of neutrons
half-life the amount of time it takes for half of the isotope in a sample to decay into a different element
index fossil a fossil of an organism that existed only during specific spans of time over large geographical areas
geological time scale a representation of the history of Earth
era lasts tens to hundreds of millions of years and consists of two or more periods
period the most commonly used units of time on the geological time scale, lasting tens of millions of years; associated with a particular type of roc
epoch the smallest units of geologic time and lasts several million years
nebula a cloud of gas and dust in space
ribozyome RNA molecules that can catalyze specific chemical reactions
cyanobacteria bacteria that can carry out photosynthesis
endosymbiosis a relationship in which one organism lives within the body of another, and both benefit from the relatioship
Paleozoic the era in which multi-cellular organisms first appeared in; began 544 million years ago
Cambrian explosion the earliest period of the Paleozoic era; involved the evolution of a huge diversity of animals
Mesozoic this era is called the Age of Reptiles (dinosaurs roamed); began 248 million years ago and ended 65 million years ago
Cenozoic the era containing two periods in which mammals evolved and diversified
primate the category of mammals with flexible hands and feet, forward-looking eyes, and enlarged brains relative to body size
prosimian the oldest living primate group; most are small and active at night
anthropoid humanlike primates
hominid walk upright, have long lower limbs, thumbs that oppose the other four fingers, and relatively large brains
bipedal animals that can walk on two legs
Created by: tuohybio1415