Earth's History and Life's Origins

The principle that processes happening today occur in the same way as they happened in the past.

The study of rock layers and their relationships to geological events.

The process of arranging rock layers and events in order of age, from oldest to youngest.

Method used to determine the numerical age of rocks or geologic events, using radioactive decay.

The largest unit of geologic time, encompassing hundreds of millions of years.

A subdivision of an Eon, typically spanning tens to hundreds of millions of years.

A subdivision of an Era, typically spanning tens of millions of years.

A division of geologic time based on significant events in Earth's history, like mass extinctions or ice ages.

The scientific study of life's history on Earth, including the origins, evolution, and extinction of different organisms.

Specialized scientists who study fossils to understand ancient life and ecosystems.

The study of Earth's history and composition, based on rock formations and their changes over time.

The process by which organisms produce offspring that are genetically different from themselves.

The development of multicellular organisms from single-celled ancestors.

The process of change in a species over time, driven by natural selection and genetic variation.

The theory that birds evolved from dinosaurs.

The theory that life on Earth arose from non-living matter in a series of chemical reactions in the early Earth's oceans, which contained a rich mixture of elements and compounds.

The period of Earth's history marked by the formation of the first organic molecules, which later led to the development of life.

A laboratory experiment conducted by Stanley Miller and Harold Urey in the 1950s that simulated the conditions of early Earth, resulting in the production of amino acids, which are the building blocks of proteins.

The proposed chemical composition of Earth's early atmosphere, which included methane, ammonia, water, and hydrogen.

The process by which the core of Earth formed, driven by the density of different elements and the heat generated by radioactive decay in the Earth's interior.

The period of Earth's history marked by the formation of the Earth from cosmic debris through a series of collisions and gravitational attraction.

The time period during which Earth's surface was molten due to the intense heat from multiple impacts by meteor-like objects, including a possible Mars-sized object.

The most accepted idea of how life originated on Earth, proposed by Alexander Oparin in the 1920s.

The Cenozoic Era is characterized by the rise of mammals and witnessed the emergence of modern mammal families like horses, whales, and primates. This era spanned from 65 million years ago to the present day, encompassing a vast array of evolutionary changes.

The Paleogene period, lasting from 65 to 23 million years ago, marked the early diversification of mammals with the appearance of early ancestors of modern groups and the emergence of families like early horses, whales, and primates. This period also witnessed the continued diversification of flowering plants.

The Neogene period, spanning from 23 to 2.6 million years ago, saw the evolution of many modern mammal families, including early horses, elephants, and bovids. This era also witnessed the rise of early hominids and the expansion of grasslands, leading to the evolution of large grazing mammals.

The Quaternary period, encompassing the last 2.6 million years, is characterized by dramatic shifts in climate, including Ice Ages, and the presence of megafauna like woolly mammoths and saber-toothed cats. This period also witnessed the global spread of early humans.

The Pleistocene epoch, encompassing the last 2.6 million years, was marked by Ice Ages, the existence of megafauna like woolly mammoths and saber-toothed cats, and the global spread of early humans.

The first eon in Earth's history, spanning over 80% of geologic time. It was characterized by the formation of the planet and lacked any significant life forms, primarily exhibiting abiotic features.

The second eon in Earth's history, marking the emergence of multicellular life and significant evolutionary processes. It is divided into three eras: Paleozoic, Mesozoic, and Cenozoic.

The first era of the Phanerozoic eon, lasting for approximately 290 million years. It witnessed the transition of plants and reptiles from water to land and is further divided into six periods.

The first period of the Paleozoic era, spanning from 542 to 488 million years ago. Characterized by the rapid diversification of life, known as the Cambrian Explosion, with dominant life forms like trilobites and early representatives of major animal phyla.

The second period of the Paleozoic era, lasting from 488 to 443 million years ago. This period saw the emergence of diverse marine life, including coral reefs, and the dominance of brachiopods, bryozoans, and trilobites.

The third period of the Paleozoic era, spanning from 443 to 416 million years ago. This period was marked by the development of the first vascular plants, the diversification of fish, and the appearance of the first land-dwelling arthropods.

The fourth period of the Paleozoic era, lasting from 416 to 359 million years ago, also known as the 'Age of Fishes'. This period witnessed the rise of various fish groups, including sharks and bony fish, and the emergence of the first tetrapods.

The fifth period of the Paleozoic era, spanning from 359 to 299 million years ago. This period saw the rise of the first reptiles, the spread of forests, and the appearance of large insects. It ended with the Permian-Triassic extinction event, marking the end of the Paleozoic era.

A geological period from 299 to 252 million years ago marked by the rise of early reptiles and the first mammal-like reptiles. Gymnosperms like conifers were dominant plants. This period ended with the largest known mass extinction in Earth's history.

The largest known mass extinction event in Earth's history, occurring at the end of the Permian Period around 252 million years ago. It wiped out over 96% of marine species and 70% of terrestrial vertebrate species.

The first period of the Mesozoic Era, from 252 to 199 million years ago. This period saw the rise of the first dinosaurs, along with early ancestors of crocodiles and mammals. It was followed by another mass extinction event.

A mass extinction event at the end of the Triassic Period, around 199 million years ago, that wiped out about 80% of species. It is believed to have been triggered by volcanic activity.

The second period of the Mesozoic Era, from 199 to 145 million years ago, known for its large sauropod dinosaurs like Brachiosaurus and Diplodocus, as well as the emergence of early bird species.

The last period of the Mesozoic Era, from 145 to 65 million years ago, characterized by the diversification of dinosaurs, the rise of flowering plants, and the appearance of many modern insect groups. It ended in another mass extinction.