Chapter 12 Word Scramble
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Term | Definition |
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 |
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