History of Life on Earth and Cellular Basis of Life

Flashcards covering the early history of Earth, major evolutionary milestones, atmospheric oxidation events, and basic biological concepts.

Earth's Formation

The event occurring about $4.5$ billion years ago (Ga).

Hadean Earth

Earth around $4.5$ billion years ago, when conditions eventually allowed water and life to develop.

Sources of Earth's Water

Asteroids are considered the primary source, while meteorites are also a plausible source.

Archean Earth

Earth around $4$ billion years ago, when water began cooling and condensing to form bodies of water, and life began evolving around $4$ to $3.8$ billion years ago.

First Form of Life

A prokaryotic, simple single-celled organism.

LUCA

An acronym standing for Last Universal Common Ancestor.

Photosynthesis

Biological process that evolved around $3.6$ to $2.5$ billion years ago, producing oxygen as a waste product and introducing free oxygen into Earth's previously oxygen-free environment.

Iron Ore / Rust Formation

Deposits formed when oxygen reacted with iron in the oceans and settled on the ocean floor, helping form rocks and the foundations of continents.

Great Oxidation Event

The period when biologically produced oxygen began accumulating in Earth's atmosphere and changing its composition.

Aerobic Respiration

A metabolic process developed by organisms that adapted to increased oxygen after first developing a metabolism to inactivate toxic oxygen.

Ozone Layer

Atmospheric layer produced with the help of atmospheric oxygen that blocks approximately $97\%$ to $99\%$ of the Sun's ultraviolet radiation.

Eukaryotic Cells

Cells evolving around $1.8$ billion years ago that contain membrane-bound organelles with different functions, formed when early prokaryotic cells developed a symbiotic relationship with organisms they engulfed.

Multicellularity

Form of biological organization that evolved around $1,500$ million years ago ($1.5$ billion years ago).

Sexual Reproduction

Biological process that evolved around $1,200$ million years ago.

Photosynthetic Eukaryotes / Algae

Organisms for which evidence of existence dates to around $1,000$ million years ago.

Terrestrial Plants

Land plants that evolved around $600$ million years ago.

Animals

Organisms that evolved around $550$ million years ago.

Characteristics of Living Things

Traits shared by living organisms: maintaining metabolism, responding to stimuli, growing/developing, reproducing, displaying heredity, evolving, and being composed of cells.

Metabolism

The chemical processes that occur within a living organism.

Heredity

The passing of traits from one generation to the next.

Cell

The fundamental structure that all living things are composed of.