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Biology Chapter 12 Whole Chapter for Test


occurs when minerals carried by water are deposited around a hard structure.

natural casts

form when flowing water removes all of the original bone or tissue, leaving just an impression in sediment.

trace fossils

record the activity of an organism; they include nests, burrows, imprints of leaves, & footprints.

amber-preserved fossils

organisms that become trapped in tree resin that hardens to amber after the tree gets buried underground.

preserved remains

form when an entire organism becomes encased in material such as ice or volcanic ash or immersed in bogs.


most rocks form in ______ rock.


the most common fossils result from _________.

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

_______ _______ is a technique that uses the natural decay rate of unstable isotopes found in materials in order to calculate the age of that material


________ are atoms of an element that have the same number of protons but a different number of neutrons.


______ is the amount of time it takes for half of the isotope in a sample to decay into a different element or its produce isotope.

4.5 billion

How old is earth in years?

index fossils

fossils of organisms that existed only during specific spans of time over large geographic areas.

geologic time scale

the _____ _____ ___ is a representation of the history of Earth.


________ last tens to hundreds of millions of years and consist of two or more periods.


_______ are the most commonly used units of time on the geologic time scale, lasting tens of of years; each ______ is associated with a particular type of rock system (same word).


________ are the smallest units of geologic time and last several million years.


a _________ is a cloud of gas and dust in space.


____________ are RNA molecules that can catalyze specific chemical reactions.


Carbon 14 has a half life of roughly ____ years.


Carbon 14 decays into what other element?


Carbon 14 may be used to date objects up to ______ years old.


Scientists use _________ to determine the age of the earth.


An example of an index fossil are the extinct marine invertebrates known as _________.

ancient life

Paleozoic means _______ ________.

middle life

Mesozoic means _____ ______.

recent life

Cenozoic means ______ ______.

Hadean Eon

The time on earth that was very hot (the first 700 million years)


Most scientists agree that free oxygen was not abundant until about __ billion years ago.


Recent studies show that ___ may have been the genetic material on early earth instead of DNA.


______ can catalyze their own replication and synthesis.


bacteria that can carry out photosynthesis.


_______ are domed, rocky structures made of layers of cyanobacteria and sediment.


a relationship in which one organism lives within the body of another, and both benefit from the relationship.


The first prokaryotes and eukaryotes could only reproduce _______.

sexual reproduction

___ ___ may have been the first step in the evolution of multicellular life.

Cambrian Explosion

The earliest part of the Paleozoic era when a huge diversity of animal species evolved.


Most of the coal used in the US formed during the ______ period of the Paleozoic era.

Mesozoic era

The era known as "The age of Reptiles"


Which era are we currently in?


What period are we currently in?


_____ make up a category of mammals with flexible hands and feet, forward looking eyes, and enlarged brains relative to body size.


_______ are the oldest living primate group and most are small and active at night.


the humanlike primates; are further subdivided into the New World monkeys, Old World monkeys, and hominoids.


_____ walk upright, have long lower limbs, thumbs that oppose the other 4 fingers, and relatively large brains.

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