Earth’s Processes and Biosphere Development

Vocabulary flashcards covering key terms from Module 5: Earth’s Processes—origin of organic molecules, hydrothermal vents, panspermia, photosynthetic life evidence, multicellularity, land colonisation, and biosphere-driven changes to Earth’s spheres.

Urey–Miller Experiment

1953 laboratory simulation of early-Earth conditions that produced organic molecules from inorganic gases.

WHAM Gases

Water vapour, Hydrogen, Ammonia and Methane—the gas mixture used in the Urey–Miller experiment.

Early-Earth Lightning Simulation

Electric sparks (electrodes) used by Urey and Miller to mimic lightning as an energy source for prebiotic chemistry.

Black Smokers

Mineral-rich hydrothermal vent chimneys on mid-ocean ridges that provide heat and chemicals for early life.

Chemosynthesis

Process by which organisms make food using inorganic chemicals (e.g., H₂S) instead of sunlight.

Archaebacteria

Anaerobic, extremophilic prokaryotes that obtain energy via chemosynthesis; inhabit black smokers today.

Catalytic Clay & Metal Deposits

Particles at hydrothermal vents that speed up chemical reactions forming complex molecules.

Panspermia

Hypothesis that amino acids or life’s precursors arrived on Earth aboard meteorites; lacks mechanism for initial synthesis.

Cyanobacteria

First photosynthetic, oxygen-producing prokaryotes; evolved >3.5 billion years ago.

Stromatolites

Layered limestone structures formed by colonies of cyanobacteria trapping sediment.

Strelley Pool Fossils

3.4 billion-year-old fossilised stromatolites in Western Australia evidencing early photosynthesis.

Photosynthesis Equation

CO₂ + H₂O → C₆H₁₂O₆ + O₂ (carbon dioxide and water produce glucose and oxygen).

End-Cryogenian Period

Time (~635 Ma) after global glaciations when multicellular life began diversifying.

Collagen Formation

Evolution of structural protein collagen that enabled larger, complex multicellular animals.

Ediacaran Fauna

Soft-bodied multicellular organisms (~635–541 Ma) evidencing early animal ecosystems.

Cambrian Explosion

Rapid diversification of animal phyla (~541 Ma) leaving abundant mineralised fossils.

Terrestrial Advantages

Fewer predators, more resources, and stable conditions that encouraged life’s move onto land.

Terrestrial Challenges

UV radiation, desiccation, and gravity obstacles faced by early land colonisers.

Ozone Layer

Stratospheric O₃ shield blocking harmful UV, enabling terrestrial life.

Arthropods (First Land Animals)

Centipedes, trilobites and relatives whose exoskeletons prevented water loss; footprints give fossil evidence.

Plant Adaptation—True Roots

Organs evolved to absorb water/nutrients from soil, improving anchorage and resource uptake.

Plant Adaptation—Seeds

Water-independent reproductive units allowing dispersal and embryo protection on land.

Plant Adaptation—Woody Stems

Lignified support tissues that counter gravity and allow vertical growth.

Animal Adaptation—Internal Fertilisation

Reproductive strategy reducing water dependence by fertilising eggs inside the body.

Animal Adaptation—Leathery (Amniotic) Eggs

Watertight shells protecting embryos from desiccation; key to reptile success on land.

Amphibian Dual Respiration

Use of gills in larval stage and lungs/skin as adults to exploit both aquatic and terrestrial habitats.

Hydrosphere Change from Cyanobacteria

Decrease in CO₂, rise in O₂, and removal of Fe²⁺ ions through precipitation of iron oxides.

Atmospheric Change from Cyanobacteria

Drop in CO₂ and CH₄, accumulation of O₂ after ocean saturation, altering greenhouse balance.

Geosphere Change—BIFs

Formation of banded iron formations as iron oxides settled onto the seafloor.

Proterozoic Acid Rain Weathering

Rain containing carbonic acids leached soluble iron ions from continental rocks into oceans.

Iron Oxide Precipitation

Reaction of O₂ with Fe²⁺ to form insoluble hematite/magnetite that sank as sediment layers.

Chert Layers

Silica-rich, iron-poor sediment bands deposited when oxygen levels temporarily fell.

Cyclic BIF Formation

Alternating iron-rich and silica-rich layers produced by fluctuating cyanobacterial oxygen production.