Fossil Records
These are the specific types of rocks where almost all fossils are found.
What are sedimentary rocks?
Earth is estimated to be approximately this many billions of years old.
What is 4.5 to 4.6 billion years?
The very first life forms on Earth belonged to this cellular domain, lacking a nucleus.
What are prokaryotes?
This rapid evolutionary event about 541 million years ago saw the sudden appearance of most major animal phyla.
What is the Cambrian Explosion?
This term refers to the ability to walk upright on two legs, a defining trait of the hominin lineage.
What is bipedalism?
This dating method determines if a fossil is older or younger than another by its position in rock layers.
What is relative dating?
This famous 1953 experiment simulated early Earth conditions and successfully synthesized organic amino acids from inorganic gasses.
What is the Miller-Urey experiment?
These layered sedimentary structures are formed by the trapping and binding of biofilms by ancient cyanobacteria.
What are stromatolites?
This geological era, known as the "Age of Reptiles," saw the rise and fall of the dinosaurs.
What is the Mesozoic Era?
Primates evolved these specific digits on their hands and feet, allowing them to grasp branches tightly.
What are opposable thumbs?
This term describes a fossil that bridges the evolutionary gap between two distinct major taxonomic groups.
What is a transitional fossil?
This is the largest, most expansive division of geological time, which is further broken down into eras.
What is an eon?
This major environmental shift occurred around 2.4 billion years ago, triggered by photosynthesizing microbes.
What is the Great Oxidation Event?
To survive on land, early plants had to evolve this waxy, waterproof outer coating to prevent drying out.
What is a cuticle?
This famous 3.2-million-year-old fossil skeleton found in Ethiopia belongs to the species Australopithecus afarensis.
Who is Lucy?
Scientists use the steady decay of this specific unstable carbon isotope to date organic remains under 60,000 years old.
What is Carbon-14?
This scientific hypothesis suggests that self-replicating RNA molecules preceded the evolution of DNA and proteins.
What is the RNA World hypothesis?
This theory explains how complex eukaryotic cells evolved by absorbing smaller, specialized prokaryotes like mitochondria.
What is the endosymbiotic theory?
This unique, soft-bodied group of organisms represents the earliest known complex multicellular life preceding the Cambrian period.
What is the Ediacaran biota?
Primates have forward-facing eyes, which provides this type of depth-perceiving vision.
What is stereoscopic (or binocular) vision?
These are widespread, short-lived fossils used by geologists to define and identify specific geological periods.
What are index fossils?
These fluid-filled spheres surrounded by a lipid membrane are considered the direct, non-living precursors to the first true cells.
What are protocells (or protobionts)?
These extreme-loving prokaryotes are often studied because they thrive in environments mimicking early Earth conditions.
What are archaea (or extremophiles)?
This major evolutionary innovation allowed early land vertebrates to reproduce completely away from water.
What is the amniotic egg?
This taxonomic group includes humans, great apes, gibbons, and New/Old World monkeys, but excludes lemurs and tarsiers.
What are anthropoids?