Origin and Evolution of Life

Nucleotides and Amino Acids Production

The first stage in the origin of life, where these building blocks were produced prior to the existence of cells.

Polymerization of Nucleotides and Amino Acids

The second stage in the origin of life, where nucleotides and amino acids formed DNA, RNA, and proteins.

Enclosure of Polymers in Membranes

The third stage in the origin of life, where polymers became enclosed within membranes.

Evolution of Cellular Properties

The fourth stage in the origin of life, where polymers enclosed in membranes acquired cellular characteristics.

Big Bang

The event that formed the universe 13-17 billion years ago.

Earth Formation

Our planet formed approximately 4.55 billion years ago.

Emergence of Life

Life on Earth is estimated to have emerged between 4 and 3.5 billion years ago.

Biogenesis

The principle that living cells originate only from pre-existing cells.

Primitive Earth Reducing Atmosphere Hypothesis

A hypothesis stating that early Earth's atmosphere had little free oxygen but contained H2O vapor, N2, CO2, and small amounts of H2 and CO.

Primordial Soup

Liquid water accumulating on a cooled Earth, forming a solution rich in organic molecules where life could originate.

Oparin and Haldane

Scientists in the 1920s who proposed the concept of abiotic (prebiotic) synthesis, suggesting spontaneous formation of organic molecules.

Abiotic (Prebiotic) Synthesis

The spontaneous formation of organic molecules from simple nonbiological sources, leading to monomers that joined to form polymers.

Miller-Urey Experiment

A 1953 experiment that demonstrated biochemicals could be produced from primitive atmospheric gases and strong energy sources, yielding HCN, CH2O, glycine, sugars, amino acids, and nitrogenous bases.

Deep-sea Vent Hypothesis

An alternative hypothesis proposing that key organic molecules arose at deep-sea vents where superheated water rich in H2S and metal ions mixed with cold seawater.

Extraterrestrial Hypothesis

An alternative hypothesis suggesting organic carbon from asteroids and comets stocked the prebiotic soup on Earth.

Carbonaceous Chondrites

Meteorites studied for the Extraterrestrial Hypothesis, found to contain significant amounts of organic carbon, amino acids, and nucleic acid bases.

Protobiont

Cell-like structures with a boundary (membrane), internal polymers containing information and enzymatic functions, and capacity for self-replication.

RNA World

A hypothesis suggesting that RNA, not DNA, was the primary genetic material and catalyst in early life, storing information, replicating, and performing enzymatic functions.

Ribozymes

RNA molecules with enzymatic functions, supporting the RNA World hypothesis.

Stromatolites

Mats of mineralized cyanobacteria, representing ancient fossil evidence of early life.

Clay Hypothesis

A hypothesis proposing that simple organic molecules polymerized into more complex organics on solid surfaces like clay, mud, or inorganic crystals.

DNA/RNA/Protein World

The current biological system where DNA stores genetic information, RNA mediates its expression, and proteins carry out most cellular functions and catalytic activities.

Fossils

Remains and traces of past life, most commonly found embedded in sediments that have converted to rock.

Paleontology

The scientific study of the fossil record.

Stratum (in geology)

A recognizable layer in a stratigraphic sequence of rocks, often containing similar fossil assemblages for a given age.

Factors Affecting the Fossil Record

Conditions like original anatomy (hard parts preserve better), organism size, population number, environment (marine/near water better), time elapsed, geological processes, and paleontologist biases that influence what is preserved and found.

Radiometric Dating

An absolute dating method used to determine the age of fossils by measuring the decay of radioactive isotopes.

Half-life

The length of time required for half of the atoms of a radioactive isotope to decay into a stable daughter product.

Mass Extinction

An event in Earth's history where a large percentage of species go extinct in a relatively short period, often influencing subsequent evolutionary patterns.

Continental Drift

The slow movement of Earth's continents (e.g., 1-10 cm/year), which impacts climate, land masses, and the distribution of life.

Precambrian Time

The earliest and longest eon in Earth's history (600 - 4,500 million years ago), comprising about 87% of geologic time and including the Hadean, Archaean, and Proterozoic Eons.

Eukaryotic Cells Emergence

The appearance of eukaryotic cells, characterized by a nucleus and membrane-bound organelles, approximately 2.5 billion years ago.

Multicellularity Emergence

The development of organisms with multiple cells working together, first appearing about 1.5 billion years ago, often linked to the Endosymbiotic Hypothesis.

Endosymbiotic Hypothesis

The theory explaining the origin of eukaryotic cells from prokaryotic organisms, particularly the origin of mitochondria and chloroplasts.

Prokaryotes

The first cells to come into existence, appearing approximately 3.5 billion years ago in aquatic environments.

Cyanobacteria

A type of prokaryote that left many ancient stromatolite fossils and was responsible for adding the first oxygen to Earth's atmosphere, leading to the evolution of aerobic species.

Ediacaran Period

A geological period at the end of the Proterozoic Eon (600-540 million years ago) during which multicellular animals, including sponges and unusual mudflat animals, first appeared.

Phanerozoic Eon

The current eon, starting approximately 543 million years ago, characterized by abundant animal and plant life, and divided into the Paleozoic, Mesozoic, and Cenozoic Eras.

Paleozoic Era

An era within the Phanerozoic Eon (543-248 million years ago) marked by three major mass extinction events and significant diversification of marine and terrestrial life.

Cambrian Explosion

A period (543-490 million years ago) during the Cambrian Period characterized by a warm, wet climate, increased oxygen, and the rapid development of all existent animal phyla.

Hox Genes

Genes involved in the regulation of body plan development, whose evolution contributed to the high diversity observed during the Cambrian Explosion.

Predator/Prey 'Arms Race'

Evolutionary pressures during the Cambrian Explosion, where the development of shells and other defenses by prey organisms drove the evolution of predators, and vice-versa.

Burgess Shale

A fossil-rich deposit known for preserving soft-bodied organisms from the Cambrian Period, providing insights into early animal diversity.

Ordovician Period

A period (490-443 million years ago) with warm, moist temperatures and high CO2, characterized by a flourishing of diverse marine invertebrates, primitive fish, and the first invasion of land by primitive plants and arthropods.

Conodonts

Tooth-like microfossils representing some of the earliest vertebrates, abundant during the Ordovician Period.

Silurian Period

A period (443-417 million years ago) of stable climate, melting glaciers, significant diversification of vertebrates (fish) and plants, and large-scale colonization of land by seedless vascular plants and arthropods.

Devonian Period

A period (417-354 million years ago), known as the 'Age of Fishes,' when gymnosperms and insects emerged, tetrapods (amphibians) first appeared, and marine invertebrates flourished.

Age of Fishes

A common name for the Devonian Period, recognizing the significant diversification and abundance of fish species during this time.

Gymnosperms

Plants with naked seeds (e.g., conifers), which first emerged during the Devonian Period.

Tetrapods

Vertebrates with four limbs, such as amphibians, which first emerged during the Devonian Period.

Carboniferous Period

A period (354-290 million years ago) characterized by rich coal deposits from vast forested swamps, diversification of plants (very large trees), flying insects, and amphibians, and the emergence of the amniotic egg (reptiles).

Amniotic Egg

A shelled egg containing amniotic fluid, which allowed reptiles to lay eggs on land, emerging during the Carboniferous Period.

Permian Period

A period (290-248 million years ago) when continental drift formed the supercontinent Pangaea, leading to drier interior regions, a shift to gymnosperm forests, dominance of reptiles, and the appearance of the first mammal-like reptiles.

Pangaea

A supercontinent that formed during the Permian Period due to continental drift.

Largest Known Mass Extinction Event

Occurred at the end of the Permian Period, resulting in the extinction of about 95% of marine species.

Mesozoic Era

An era (248-65 million years ago), known as the 'Age of Reptiles,' characterized by a consistently hot climate and dry terrestrial environments, and the dominance of dinosaurs.

Age of Reptiles

A common name for the Mesozoic Era, reflecting the dominance of dinosaurs and other reptiles during this time.

Triassic Period

A period (248-201 million years ago) when gymnosperms were dominant, reptiles were abundant (first dinosaurs appeared), and the first true mammals emerged.

Jurassic Period

A period (201-145 million years ago) during which dinosaurs achieved enormous size, mammals remained small, and the first birds appeared.

Cretaceous Period

A long period (145-65 million years ago) during which dinosaurs began their decline, culminating in the K-T extinction, and mammals began an adaptive radiation into vacated habitats.

K-T Extinction

A mass extinction event at the boundary of the Cretaceous and Tertiary periods (65 million years ago), caused by meteorite impact and volcanism, leading to the demise of dinosaurs.

Adaptive Radiation

The rapid diversification of a group of organisms into new forms filling different ecological niches, such as mammals after the K-T extinction.

Cenozoic Era

The current era (65 million years ago to today), known as the 'Age of Mammals,' where tropical conditions were replaced by a colder, drier climate, and mammals, birds, fishes, and insects diversified.

Age of Mammals

A common name for the Cenozoic Era, due to the extensive adaptive radiation and dominance of mammals during this time.

Quaternary Period

The most recent geological period (1.8 million years ago to today), often referred to as the 'Age of Man' (Hominids), with Homo sapiens appearing 130,000 years ago.

Primate Evolution

The evolutionary lineage of organisms including lemurs, tarsiers, monkeys, apes, and humans, all adapted for climbing trees with rotating shoulder joints, grasping digits, and stereoscopic vision.

Bipedalism

The ability to walk upright on two legs, a key characteristic of humans (Homo).

Opposable Thumb

A thumb that can touch all other fingers, a defining characteristic of humans that enhances dexterity.

6th Mass Extinction

The ongoing mass extinction event, also known as the Holocene or Anthropocene Extinction, characterized by significant species die-offs attributed to human activities.

Global Superpredators

A term used to describe humans due to their widespread impact on animal populations and ecosystems, leading to significant declines in wildlife.

Atmospheric CO2 Rise

The human-induced increase in carbon dioxide in the atmosphere, significantly greater and faster than natural increases observed in geological history.