Anything that changes over time.

A trait that helps an organism survive and reproduce.

A model of the major events and diversity of life forms present in Earth's history beginning when Earth was formed and goes on until the present.

Earliest span of time in Earth's history that included the formation of the Earth and the first evidence of single celled life.

A scientist who studies all things related to the Earth including what the Earth is made of and how it was formed.

The era of geologic time from about 540 to 245 million years ago characterized by a great diversity of marine invertebrate animals.

The era of geologic time from about 230 to 65 million years ago, characterized by the appearance of flowering plants and the dominance and extinction of dinosaurs.

Era of geologic time, from about 65 million years ago to the present, characterized by the formation of modern continents and the dominance of many mammals.

The largest division of geologic time, made up of two or more eras.

This is one of the three long units of geologic time between Precambrian time and present time.

A smaller division of time than an era, but larger than an epoch.

On the geologic time scale, this is a span of time smaller than a period.

The collection of fossils and their placement in chronological order that documents the existence, diversity, extinction, and change of many life forms and environmental changes throughout the history of life on Earth.

The loss of a large number of species within a relatively short period of geological time.

An animal lacking a backbone.

Extinct marine arthropods that were abundant during the Paleozoic era.

Marine invertebrate animals that lived during the Paleozoic era resembling clams.

Current period of the Cenozoic Era in the geologic time scale

An extremely rapid development of new animal species that occurred at the beginning of the Paleozoic era and Phanerozoic eon.

The approximate age of an object determined by the order of rock layers and index fossils.

An extinct organism that lived only a short part of Earth's history; found over a wide area of Earth; and is unique used to help find the relative age of rock layers.

A law that states that each rock layer is older than the one above it.

True age of a rock or fossil.

When an asteroid or comet strikes the Earth's surface causing a large number of species to go extinct.

Organisms that live in the ocean or other bodies of water.

The variety of life in the world or in a particular habitat or ecosystem.

A group of living organisms consisting of similar individuals capable of breeding.

Mineral replacements, preserved remains, or traces of organisms from 30,000 years or more in the past.

The natural processes that convert an organism into a fossil.

Closely related organisms often share similar structures in their bodies, despite different lifestyles. The simplest explanation for such similarities is that both species descended from a common ancestor.

The arrangement of things in order based on time.

Preventing all or some of an organism from being destroyed and remaining fossilized.

A fossil that preserves the impression of the hard parts of an organism, such as a shell or bone.

A fossil formed when sediment fills the inside or covers the outside of a dead organism and the organism's remains do not persist, leaving just the shape.

Species of organism living in the same area.

Physical attributes of an organism such as hair color, leaf shape or behavioral characteristics, such as hibernation, and migration.

Differences in genes between individual members of a population.

The process of organisms that are better adapted to their environment are more likely to survive and produce more offspring with similar advantageous traits.

Changes in the environment due to volcanic eruptions, global warming, global cooling during ice ages, changes in oxygen levels in seawater, or a massive impact from an asteroid or comet.

Have caused extinctions in more recent times, such as the cutting of the rain-forest regions, removing natural habitats, over-harvesting, and pollution.

The place or function of an organism within its ecosystem

Taking more from the land, or sea than it can replace. It includes extreme farming, grazing, fishing, and using fresh water.

Name given to the last 11,700 years of the Earth's history — the most recent time span since the end of the last major "ice age."

Sudden disaster of immense proportions that is, accompanied by tremendous loss of life.

The greatest extinction ever in Earth's history caused by widespread volcanic activity that ended the Paleozoic era.

More than enough; plentiful

Relationship between two variables

A type of representation that shows what a view would look like when cutting through an object

Before recorded history

An entire grouping of organisms such as a kingdom, phylum, class, order, family, genus, or species used in classification.

A group of organisms born and living at the same time.

Groups of related species of organisms.

The collection of test subjects selected for observation in an scientific study. The large the better!

To show clearly.

Spread out over an area.

Evidence that does not involve direct observation such as inferences.

Evidence that can be observed with our senses.

A group of ecosystems with similar climates and organisms.

To improve or make better.

Left over or remaining.