Ch 22: GEOBIOLOGY Life Interacts with Earth

Geobiology

Study of interactions between life and Earth’s physical and chemical systems

Geology

Study of Earth’s physical and chemical processes past and present

Biology

Study of living organisms including structure, function, and evolution

Biosphere

Zone of Earth where life exists and interacts with environment

Building blocks of life

Carbon, hydrogen, oxygen, water, nutrients, energy

Water importance

Life is 50–95% water and exists in aqueous environments

Key nutrients

Phosphorus, nitrogen, potassium, sulfur

Energy sources for life

Sunlight, chemical reactions, geothermal energy

Organic compounds

CH4, hydrocarbons, amino acids essential for life

CO2 role

Present in atmosphere/oceans and abundant in early Earth

Weathering role

Releases nutrients from volcanic rocks into environment

Biological kingdoms

Bacteria, Archaea, Eukaryotes

Cyanobacteria age

~2700–2100 Ma origin

Universal ancestor

Common origin point of all life

Autotrophs (producers)

Organisms that create their own food via photosynthesis or chemosynthesis

Heterotrophs (consumers)

Organisms that obtain energy from other organisms

Photosynthesis equation

6H2O + 6CO2 + energy → C6H12O6 + 6O2

Photosynthesis organisms

Plants and cyanobacteria

Respiration equation

C6H12O6 + 6O2 → 6H2O + 6CO2 + energy

Respiration role

Converts sugars into usable energy

Photosynthesis impact

Introduced oxygen into atmosphere

Habitable zone

Region around star allowing liquid water to exist

Too close to star

Water vaporizes due to high temperature

Too far from star

Water freezes

Habitable planet criteria

Distance, mass, density, atmosphere, magnetic field, plate tectonics

Sun surface temperature

~6000 K

Drake Equation

Formula estimating number of extraterrestrial civilizations

Fermi Paradox

High probability of life vs lack of evidence for extraterrestrial life

Miller-Urey experiment

Simulated early Earth atmosphere to produce organic compounds

Miller experiment date

Early 1950s

Prebiotic atmosphere composition

CH4, NH3, H2, H2O, no O2

Energy source in experiment

Electrical sparks simulating lightning

Prebiotic soup

Hypothesis that organic molecules formed in early oceans

Amino acids

Building blocks of proteins and DNA

Extraterrestrial organics

Amino acids found in interstellar clouds

Carbonaceous chondrites

Meteorites containing organic compounds

Meteorite contribution

Delivered organics and volatiles to early Earth

Hydrothermal vents

Deep-sea environments supporting life via chemical energy

Black smokers

Hydrothermal vents emitting mineral-rich fluids

Chemosynthesis

Energy production from chemical reactions instead of sunlight

Extreme environments

Conditions like high heat or acidity where life can still exist

Stromatolites

Layered structures formed by cyanobacteria

Oldest stromatolites

~3.4 Ga

Stromatolite formation

Cyanobacteria trap sediments and precipitate minerals

Cyanobacteria role

Produced oxygen through photosynthesis

Calcium carbonate formation

CaO + CO2 → CaCO3

Biomineralization

Organisms forming minerals like calcite or magnetite

Banded Iron Formations (BIFs)

Layered iron-rich sedimentary rocks

BIF age

~2–3 Ga

BIF composition

Alternating iron oxides (Fe2O3, Fe3O4) and silica layers

Fe2+ behavior

Soluble in low oxygen conditions

Fe3+ behavior

Insoluble in high oxygen conditions

BIF formation mechanism

Oxygen reacts with Fe2+ forming Fe3+ precipitates

Oxygen accumulation timing

~2.7–2.1 Ga after iron was depleted

Great Oxygenation Event

Rise of oxygen in atmosphere ~2 Ga

Ozone formation

O2 forms O3, protecting Earth from UV radiation

Ozone layer importance

Enabled life to move onto land (~460 Ma)

Cambrian explosion

Rapid diversification of life ~530 Ma

Pre-Cambrian life

Mostly simple, single-celled organisms

Cambrian causes

Increased oxygen, environmental changes, skeleton development

Evolutionary radiation

Rapid increase in biodiversity

Mass extinction

Large-scale loss of species over short time

Big Five extinctions

Five major extinction events in Earth history

K-T boundary

Boundary marking end-Cretaceous extinction (~65 Ma)

Chicxulub impact

Meteorite ~10 km diameter caused extinction

Impact crater size

180 km diameter

Impact energy

Millions of times stronger than nuclear explosions

Impact aftermath

Dust clouds blocked sunlight and halted photosynthesis

Iridium evidence

Extraterrestrial element found at K-T boundary

Impact temperature

Fireball ~10,000°C

Acid rain effect

Sulfuric and nitric acids fell after impact

Flood basalts

Massive volcanic eruptions releasing CO2

Siberian flood basalts

Major CO2 emission event ~250 Ma

Volcanic gases

CO2, H2O, sulfur compounds

Volcanic extinction mechanism

Climate change and atmospheric alteration

Fossil fuels

Formed from organic matter after Cambrian explosion

Fossil fuel limitation

Nonrenewable resource

Keeling Curve

Measurement of rising atmospheric CO2

CO2 increase

~320 ppm to ~420 ppm since 1950s (~32% increase)