Flashcards in Chapter 5 Section 3 Deck (18):
1
usually only what parts of the organism become fossils
hard parts such as bones or shells
2
most fossils form how
when organisms that die become buried in sediments
3
what are sediments
particles of soil and rock
4
how do petrified fossils form
they form when minerals dissolved in water soak into the buried remains and gradually replace the remains changing them into rock
5
what is a mold
it is a hollow space in sediments in the shape of an organism or part of an organism
6
what is a cast
A cast is a copy of the shape of the organism that made the mold
7
organisms can be preserved in what
ice or other materials like amber or tree sap
8
what two ways can scientist determine a fossil's age
relative dating and radioactive dating
9
scientists use relative dating for what
to determine which of two fossils is older
10
radioactive dating is what
it is a technique used by scientists to determine the actual age of fossils
11
what are radioactive elements
they are unstable elements that decay, or break down, into different elements
12
what is the half life of an element
it is the time it takes for half of the atoms in a sample to decay
13
what is the fossil record
it is what the millions of fossils that scientists have collected is called
14
what does extinct mean
it is a term used to describe a species that has no members of it alive.
15
what is the calendar of the earth referred to as
the geologic time scale
16
what is a mass extinction
it is when many types of organisms become extinct at the same time
17
what is gradualism
it is a theory of evolution where evolution occurs slowly but steadily.
18