Fossils
What are preserved remains of living things called?
Fossils
What type of rock is made of hardened sediment?
Sedimentary rock
What does the law of superposition state?
The oldest rock layer is at the bottom, and layers get younger toward the top
What are the four main time divisions geologists made?
Precambrian, Paleozoic, Mesozoic, and Cenozoic
What does it mean if an organism is extinct?
It no longer exists and will never live again on Earth
Who are scientists that study fossils?
Paleontologists
What is an extremely thin coating of carbon on rock called?
Carbon film
What is the age of a rock compared to other rocks called?
Relative age
What are different time periods called?
Eras
What are animals without backbones called?
Invertebrates
What type of fossil forms when minerals replace all or part of an organism?
Petrified fossils
What type of fossil provides evidence of the activities of ancient organisms?
Trace fossils
What is the number of years since a rock formed called?
Absolute age
What are eras subdivided into?
Periods
What are animals with backbones called?
Vertebrates
What kind of fossil leaves a hollow area in sediment in the shape of an organism?
Mold
What are five different kinds of fossils?
Body fossils, molds, cast fossils, petrification fossils, footprints
What process causes elements to break down by releasing particles and energy?
Radioactive decay
What are the subdivided periods of the Cenozoic Era called?
Epochs
What type of animal lives part of its life on land and part in water?
Amphibian
What kind of fossil forms when a mold is filled in, creating a copy of the organism?
Cast
What are three ways animal remains can be preserved?
Unaltered soft or hard parts, altered hard parts, and trace fossils
What is the time it takes for half of the radioactive atoms to decay?
Half-life
What are the three periods in the Mesozoic Era?
Triassic, Jurassic, and Cretaceous
What is it called when many types of living things become extinct at the same time?
Mass extinction