Origin & Development of the Biosphere
This 1950s experiment used water, methane, ammonia, and hydrogen sparked with electricity to simulate early Earth conditions and produced amino acids.
What is the Urey-Miller (Miller-Urey) experiment?
Plants needed this type of tissue to develop before they could grow tall and transport water and nutrients away from a constant water source.
What is vascular tissue?
Cyanobacteria produced this gas as a waste product of photosynthesis, which built up in the atmosphere over billions of years.
What is oxygen?
This term describes the cyclical process of continents joining together into a single landmass and later breaking apart, repeating over hundreds of millions of years.
What is the (plate tectonic/supercontinent) supercycle?
This type of fossil forms when an organism decays after burial, leaving a cavity in the rock that preserves the shape of its exterior.
What is a mould fossil?
These deep-sea hydrothermal vent ecosystems support communities independent of sunlight, offering an alternative hypothesis for where organic molecules first formed.
What are black smokers?
This waxy, waterproof layer on plant surfaces (and later, a feature of animal skin/exoskeletons) helped prevent water loss once organisms moved onto land.
What is a cuticle?
This name is given to the dramatic rise in atmospheric oxygen roughly 2.4 billion years ago, largely caused by photosynthesising cyanobacteria.
What is the Great Oxidation Event (Great Oxygenation Event)?
This most recent supercontinent existed from roughly 335 to 175 million years ago before breaking apart into the continents we recognise today.
What is Pangaea?
This type of fossil forms when sediment or minerals fill a mould left by a decayed organism, creating a replica of its original shape.
What is a cast fossil?
This hypothesis proposes that organic molecules or microbial life arrived on Earth from space via meteorites or comets.
What is panspermia?
Considered among the first land plants, these simple, non-vascular plants still rely on moist environments to reproduce, showing an incomplete transition to land.
What are bryophytes (e.g. mosses/liverworts)?
Before oxygen accumulated in the atmosphere, it first reacted with dissolved iron in this sphere, causing iron to precipitate out of seawater.
What is the hydrosphere (the oceans)?
This force, driven by heat from the Earth's core and mantle, is the underlying driver of plate movement throughout the supercycle.
What is mantle convection?
Footprints, burrows, and coprolites are all examples of this type of fossil, which records evidence of an organism's activity rather than its body.
What is a trace fossil?
These layered sedimentary structures, built by cyanobacteria, provide some of the earliest fossil evidence for photosynthetic life on Earth.
What are stromatolites?
This group of arthropods, including early myriapods and insects, are thought to be among the first animals to colonise land, aided by an existing waterproof exoskeleton.
What are arthropods?
These distinctive, alternating layers of iron-rich and silica-rich rock were formed as dissolved oceanic iron reacted with rising oxygen levels and settled on the seafloor.
What are banded iron formations (BIFs)?
When continents merge into a supercontinent, interior regions become isolated from oceanic moisture, typically producing this type of extreme, dry climate.
What is an arid/desert climate?
To be useful for dating rock layers across the globe, this type of fossil must come from a species that was widespread, existed for a short geological time, and evolved rapidly.
What is an index fossil?
This process, carried out by early cyanobacteria, released oxygen into Earth's atmosphere and is linked to the Great Oxidation Event, radically changing the biosphere.
What is photosynthesis?
Vertebrates transitioning to land needed to evolve this paired body structure, originally used for swimming, into limbs capable of supporting body weight.
What are lobed/paired fins (leading to limbs)?
Once dissolved iron in the oceans was largely used up, oxygen began accumulating here instead, eventually enabling aerobic life and altering global climate.
What is the atmosphere?
The breakup of a supercontinent creates new coastlines and separates landmasses, often driving this biological process as populations become isolated and evolve independently.
What is speciation (or allopatric speciation)?
This principle states that in an undisturbed sequence of sedimentary rock layers, the oldest layers are at the bottom and the youngest are at the top.
What is the law/principle of superposition?
This fauna, characterised by soft-bodied, largely immobile organisms, predates the Cambrian explosion and represents some of the earliest evidence of multicellular life.
What is the Ediacaran fauna?
This reproductive innovation freed early reptiles from needing to return to water to reproduce, completing the vertebrate conquest of land.
What is the amniotic egg?
This layer of the atmosphere, formed from oxygen (O2) converted into O3 by UV radiation, was critical in shielding Earth's surface from harmful radiation and enabling life to later colonise land.
What is the ozone layer?
Rifting and volcanic activity associated with supercontinent breakup can release large volumes of this gas, influencing long-term global temperature through the greenhouse effect.
What is carbon dioxide (CO2)?
This principle, often summarised as "the present is the key to the past," assumes that the geological processes observed today have operated in the same way throughout Earth's history, allowing scientists to interpret past events like mass extinctions.
What is uniformitarianism?