15.1 Flashcards
What is a fossil?
a trace of a long-dead organism. Often found in sedimentary rock.
What is sedimentary rock?
formed when sediment such as dust, sand, or mud is desposited by wind or water.
What is a mold fossil?
an imprint in rock in the shape of an organism
What is the law of superposition?
states that successive layers of rock or soil were deposited on top of one another by wind or water.
What is a stratum?
the lowest strtum, or layer, in a cross section of Earth is the oldest while the top stratum is the most recent. Fossils within a single stratum are around the same age.
What is mass extinction?
brief periods during which large numvers of species would dissapear
What are three examples of fossils?
1) mold fossil 2) footprints 3) amber 4) fossilized marks on the bones of some human ancestors
How did the law of superposition allow paleontologists to assign relative ages to fossils?
they could tell how old they were based on what stratum they were found in
In which geological era did the first organism arrive?
precambrian era
How do biogeographic ovsrvations suggest that a modification process caused new species to arise?
by a comparison of recently formed fossiltypes with types of organisms in the same geographical area. this shows that new organisms arise in areas where similar forms already live.
