a set of statements or principles devised to explain a group of facts or phenomena, especially one that has been repeatedly tested or is widely accepted and can be used to make predictions about natural phenomena.
theory
A theory that the various types of animals and plants have their origin in other preexisting types and that the distinguishable differences are due to modifications in successive generations
evolution
describes a species of animals that once lived on Earth but which no longer exists
extinct
a group of organisms that share similar characteristics and can mate with each other to produce offspring
species
the information about Earth's history that can be gathered from fossils
fossil record
the average weather conditions in an area
climate
all the living and nonliving things that surround an organism
environment
layers of gas that surround a planet
atmosphere
a layer or line of rock above or below another body of rock
rock layer
measurement of the amount of radioactive material (usually carbon 14) that an object contains; can be used to estimate the age of the object
radioactive dating
the age given in years, of a fossil, a rock, a feature, or an event; usually determined through radiometric dating
absolute age
extremely old
ancient
evidence that an organism once existed in an area
fossil
an organism that is made of many cells, cannot make its own food, and can move during at least part of its life
animal
an organism that is made up of many cells, makes its own food through photosynthesis, and cannot move
plant
the third planet from the Sun; the planet on which we live
earth
any individual living thing
organism
fossilized evidence of plant existence or animal movements such as root channels, footprints, and burrows
trace fossil
to break down into simple nutrients
decompose
an element that makes up about 21% of Earth's atmosphere; a gas in Earth's atmosphere and in water that living organisms breathe
oxygen
to break down or wear away
decay
an extinct organism with reptile and birdlike features
dinosaur
the physical or chemical breakdown of rocks and minerals into smaller pieces or aqueous solutions on Earth's surface
weathering
When soil is moved from one location to another by wind or water. After rocks have been broken down, the small particles are transported to other locations by wind, water, ice, and gravity.
erosion
the process during which rocks are formed, change, wear down, and are formed again over long periods of time
rock cycle
a fossil resin from tree sap, usually a translucent, yellow-brown color, which may contain insects or other organisms
amber
an element that is found in almost all compounds that make up living things
carbon
a natural, solid substance found in rocks; each mineral has a specific chemical makeup
mineral
solid material, moved by wind and water, that settles on the surface of land or the bottom of a body of water
sediment
a fossil that forms when the remains of an organism leave an imprint in the sediment after the organic material has been completely replaced
mold
a type of fossil formed when sediment fills a mold of an organic object such as a fossil shell, creating a replica of that object made of sediment
cast
the process of comparing objects or events to determine which are younger or older, without knowing their specific ages
relative dating