The History of Life

Science

Human-like primates, including new world monkeys, old world monkeys, and hominoids

Anthropoid

Human-like primates, including new world monkeys, old world monkeys, and hominoids. Anthropoid. Anthropoids are a group of primates that include monkeys, apes, and humans.

Walking on two legs, like a human, ostrich, or kangaroo

Bipedal

Walking on two legs, like a human, ostrich, or kangaroo. Bipedal. In science, bipedal means moving using two legs.

A rapid increase in the diversity of lifeforms that occurred during the Paleozoic era

Cambrian explosion

A rapid increase in the diversity of lifeforms that occurred during the Paleozoic era. Cambrian explosion. The Cambrian explosion was a period around 541 million years ago when there was a sudden increase in different types of animals on Earth.

States that mitochondria and chloroplasts evolved from eukaryotic cells that entered prokaryotic cells

Endosymbiotic theory

States that mitochondria and chloroplasts evolved from eukaryotic cells that entered prokaryotic cells. Endosymbiotic theory. This theory suggests that some organelles in eukaryotic cells originated from ancient symbiotic relationships where one cell lived inside another.

A unit of geologic time longer than an age but shorter than a period

Epoch

A unit of geologic time longer than an age but shorter than a period. Epoch. An epoch is a specific time frame in Earth's history marked by significant events or changes in climate, life, or geography.

The second-longest unit of geologic time, it is divided into periods

Era

The second-longest unit of geologic time, it is divided into periods. An era is a long span of time marked by significant events or changes in Earth's history.

A timeline of Earth's history based on major changes

Geologic time scale

A timeline of Earth's history based on major changes. Geologic time scale. The geologic time scale is a system used by scientists to organize Earth's history into different periods based on significant geological and biological events.

The time it takes for half the atoms of a radioactive isotope to decay

Half-life

The time it takes for half the atoms of a radioactive isotope to decay. Half-life. In science, half-life is the time it takes for half of a substance to break down or change into something else.

A fossil from an organism that existed for a short time, it is used to determine the age of other fossils

Index fossil

A fossil from an organism that existed for a short time, it is used to determine the age of other fossils. Index fossil. An index fossil helps scientists figure out how old other rocks or fossils are because it comes from a species that lived for a short, specific time period.

When many species become extinct at the same time

Mass extinction

When many species become extinct at the same time, mass extinction. Mass extinction is a rapid and widespread decrease in the number of species on Earth.

A scientist who studies fossils

Paleontologist

A scientist who studies fossils. Paleontologist. A paleontologist is a scientist who explores ancient life by studying fossils, like dinosaur bones and plant imprints.

A unit of geologic time that lasts tens of millions of years, it is longer than an epoch but shorter than an era

Period

A unit of geologic time that lasts tens of millions of years, it is longer than an epoch but shorter than an era. Periods are segments of time in Earth's history used by scientists to organize geologic events.

The theory that Earth's crust is made of moving plates

Plate tectonics

The theory that Earth's crust is made of moving plates plate tectonics. Plate tectonics is the scientific idea that the Earth's surface is divided into large pieces that slowly move and interact, causing earthquakes and forming mountains.

Mammals with features like opposable thumbs, forward looking eyes, and a large brain, like humans, monkeys or apes

Primate

Mammals with features like opposable thumbs, forward-looking eyes, and a large brain, like humans, monkeys, or apes. Primate. A primate is a type of mammal that typically has these traits, allowing them to live in complex environments.

Comparing the amount of radioactive and nonradioactive isotopes to determine rock age

Radiometric dating

Comparing the amount of radioactive and nonradioactive isotopes to determine rock age. Radiometric dating. It's a scientific method used to date materials like rocks by measuring the decay of radioactive isotopes within them.

A method of comparing fossils or rocks to determine which is older

Relative dating

A method of comparing fossils or rocks to determine which is older. Relative dating. It tells us the order in which events happened, without knowing their exact ages.

The theory that life can arise from nonliving things

Spontaneous generation

The theory that life can arise from nonliving things. Spontaneous generation. This is an outdated scientific theory that suggested living organisms could suddenly develop from nonliving matter.