Earth Science and Ecology

CHNOPS Elements

Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, and Sulfur; six biogenic elements that form ~95% of living biomass.

Potassium, Sodium, Calcium Role

Macro-nutrients necessary for biological functions, but NOT part of the core CHNOPS six elements.

Ecological Niche

The functional role, position, and resource utilization of an organism within its community (its "profession").

Habitat

The specific physical location or environment where an organism lives (its "address").

Levels of Biological Organization

Highest to Lowest: Biosphere -> Ecosystem -> Community -> Population -> Organism -> Organ System -> Organ -> Tissue -> Cell -> Organelle -> Molecule -> Atom.

Biosphere

The global ecological system integrating all living beings and their physical environment.

Ecosystem

A biological community interacting with its abiotic physical environment.

Community

All interacting populations of different species occupying a defined geographic area.

Population

A group of interbreeding individuals of the same species living in a specified area.

Organism

An individual living entity (e.g., a single animal, plant, or bacterium).

Keystone Species

A species that exerts a disproportionately large influence on ecosystem structure and stability relative to its abundance.

Endemic Species

A species natively restricted to a single specific, defined geographic region.

Invasive Species

Non-native organisms introduced to an ecosystem that outcompete native species and disrupt ecological balance.

Indicator Species

Organisms whose presence, absence, or health reflects environmental conditions or ecosystem quality.

Mutualism (+/+)

A symbiotic interaction where both participating species benefit (e.g., mycorrhizal fungi and plant roots).

Commensalism (+/0)

A symbiotic interaction where one species benefits while the other is neither helped nor harmed (e.g., barnacles on whales).

Parasitism (+/-)

A symbiotic interaction where one organism benefits at the direct expense of its host.

Predation & Competition

Non-symbiotic interspecific interactions driving natural selection and food web structure.

Habitable Zone ("Goldilocks Zone")

The distance range from a star where surface temperatures allow liquid water to persist under an atmosphere.

LUCA (Last Universal Common Ancestor)

The inferred shared ancestor of all modern life, identified via shared genes across Archaea, Bacteria, and Eukaryota.

LUCA Environment

Oxygen-free, high-temperature environment harvesting energy from deep-sea chemical gradients.

Prokaryotes vs. Eukaryotes

Prokaryotes lack a membrane-bound nucleus and organelles; Eukaryotes possess linear DNA within a nucleus and complex organelles.

Autotrophs vs. Heterotrophs

Autotrophs synthesize organic carbon directly from inorganic sources; Heterotrophs consume organic carbon from other organisms.

Endosymbiosis

Evolutionary process where host cells engulfed free-living prokaryotes, transitioning them into organelles (mitochondria & chloroplasts).

Evidence for Endosymbiosis

Circular DNA, double membranes, independent binary fission, and genetic homology with bacteria.

Cambrian Radiation (Explosion)

Rapid biological diversification (~542-540 Ma) yielding major animal phyla, exoskeletons, and compound eyes.

Mass Extinctions

Catastrophic events causing widespread species loss, altering ecosystems and triggering adaptive radiation among survivors.

Bioenergetics

The flow of energy through living systems at cellular and ecosystem levels.

Metabolism

The sum of all energy-consuming (anabolic) and energy-generating (catabolic) chemical reactions in a cell or organism.

First Law of Thermodynamics

Energy cannot be created or destroyed; it can only be transferred or transformed from one form to another.

Second Law of Thermodynamics

Energy transfers are inefficient, producing unusable heat energy and increasing systemic entropy.

Entropy

A measure of randomness or disorder in a system; living organisms require continuous energy inputs to maintain low entropy.

Open System

A physical system that freely exchanges both energy and matter with its surroundings (all living organisms are open systems).

Potential Energy

Stored energy associated with an object's position, spatial structure, or chemical state.

Chemical Energy

A form of potential energy stored within molecular bonds (e.g., ATP, sugars) released when bonds break.

Kinetic Energy

The energy associated with motion (e.g., flowing water, cellular movement, heat).

Photoautotroph

Organism that uses solar radiation to synthesize organic compounds from CO2 (e.g., plants, cyanobacteria).

Chemoautotroph

Organism (bacteria/archaea) that oxidizes inorganic compounds (H2S, methane) for energy in lightless environments.

Trophic Level

The positional step or energy level an organism occupies within a food chain or web.

Producers

Autotrophic organisms forming the foundational base of a food chain.

Primary Consumers

Herbivores that feed directly on producers.

Secondary Consumers

Carnivores that feed on primary consumers.

Tertiary Consumers

Carnivores that feed on secondary consumers.

Apex Consumer

Top predators at the highest trophic level with no natural predators.

Decomposers & Detritivores

Organisms in detrital food webs that break down decaying organic matter, recycling abiotic nutrients.

Biome

A major regional ecological community defined by climate conditions (temperature and precipitation) and characteristic plant/animal adaptations.

Tundra Biome

Extremely cold, dry biome; permafrost layer prevents deep rooting; dwarf shrubs, mosses, lichens; treeless plains with low vegetation.

Savanna Biome

Warm tropical biome with distinct wet/dry seasons; grasslands scattered with drought-tolerant trees (acacias); grazing herbivores.

Desert Biome

Arid biome (

Deciduous Forest Biome

Moderate rain with 4 distinct seasons; broadleaf trees (oak, maple) shedding leaves in autumn; rich leaf litter/humus.

Wetlands Biome

Biome with permanently/seasonally saturated hydric soils; hydrophytic vegetation (reeds, mangroves); standing water and high biodiversity.

Biomass

Total mass of living organic matter per unit area or volume in a habitat or ecosystem.

Production

The absolute amount of energy or organic material fixed by a system (measured in grams or Joules).

Productivity

The rate at which organic matter is produced per unit area per unit time (e.g., g/m²/yr or kcal/m²/yr).

Primary Production

Generation of new organic biomass via direct CO2 fixation by autotrophs.

Photosynthesis Equation

6CO2 + 6H2O + Sunlight -> C6H12O6 + 6O2 (Light reactions split H2O in thylakoids; Calvin cycle fixes CO2 in stroma).

Chemosynthesis

Synthesis of organic matter by chemoautotrophs using inorganic chemical oxidation (e.g., H2S) near deep-sea vents.

Respiration (R) Equation

C6H12O6 + 6O2 -> 6CO2 + 6H2O + ATP (Releases chemical bond energy for work, yielding metabolic heat).

Nitrogen Cycle: Plant Absorption

Plants cannot use atmospheric N2 gas directly; soil bacteria must convert it into bioavailable forms.

Nitrogen Fixation

Process where diazotrophic bacteria (Rhizobium in legume roots, Azotobacter, cyanobacteria) convert atmospheric N2 into NH3 or NH4+.

Nitrification

Conversion of ammonium (NH4+) into nitrites (NO2-) and then nitrates (NO3-) by soil bacteria for plant absorption.

Assimilation (Nitrogen)

Absorption of nitrates (NO3-) by autotrophs to synthesize amino acids, proteins, and nucleic acids.

Ammonification

Breakdown of nitrogenous organic waste and dead tissue back into ammonium (NH4+) by decomposers.

Denitrification

Process where anaerobic soil bacteria convert nitrates (NO3-) back into atmospheric N2 gas.

Biological Carbon Cycle (Short-Term)

Rapid carbon flux driven by photosynthesis and respiration across living biomass, atmosphere, and oceans on day-to-decadal scales.

Geological Carbon Cycle (Long-Term)

Slow carbon flux controlled by rock weathering, volcanism, subduction, and fossil fuel formation over millions of years.

Early Earth Atmosphere

Young Earth (~4.0 Ga) possessed an anoxic atmosphere rich in CH4, NH3, H2, and CO2, with intense surface UV radiation.

Hydrothermal Vent Life Origin

Deep-sea vents shielded early life from surface UV radiation, providing minerals and chemical/thermal gradients.

White Smokers vs. Black Smokers

White Smokers are alkaline, lower-temperature, methane-rich vents (Lost City) ideal for life's origin; Black Smokers are superheated, highly acidic vents.

G Stars (Sun-like)

Solar-type stars; rare (~7%); ~10 billion year lifespan; luminous and supports life, but shorter lived than smaller stars.

M Dwarfs (Red Dwarfs)

Most abundant stars (~75%); burn extremely slowly for trillions of years; close orbital zones expose planets to violent flares and radiation.

K Dwarfs (Orange Dwarfs)

"Goldilocks stars"; 3x more abundant than G stars; 15-45 billion year lifespan; stable radiation without severe flares.

Hadean Eon (4.5 - 4.0 Ga)

Earth formation; heavy bombardment, severe volcanism, and no initial liquid surface water.

Archean Eon (4.0 - 2.5 Ga)

Origin of first single-celled prokaryotes (~3.8-4.0 Ga); anoxic atmosphere; oldest fossil evidence in stromatolites (~3.5 Ga).

Proterozoic Eon (2.5 Ga - 542 Ma)

Great Oxidation Event (~2.5 Ga); Banded Iron Formations; first aerobic eukaryotes (~1.0-1.5 Ga); soft-bodied multicellularity (~650 Ma).

Great Oxidation Event (~2.5 Ga)

Cyanobacteria flood atmosphere with O2 via photosynthesis; causes global glaciation and mass die-offs of obligate anaerobes.

Phanerozoic Eon (542 Ma - Present)

Eon marked by the emergence and diversification of complex, visible multicellular life.

Cambrian Period (542 - 485 Ma)

Cambrian Explosion; hard shells, Trilobite compound eyes, early chordates (Pikaia).

Ordovician-Silurian (485 - 419 Ma)

Life colonizes land (~400 Ma); fungi (Tortotubus - 440 Ma) build soil; early spore plants and invertebrates.

Devonian Period (419 - 359 Ma)

"Age of Fishes"; armored Placoderms dominate; evolution of first tetrapods from lobe-finned fish.

Carboniferous Period (359 - 299 Ma)

Extensive coal swamps; high atmospheric O2 allows giant arthropods; evolution of the amniotic egg.

Permian Period (299 - 251 Ma)

Dominated by synapsids (Dimetrodon); ends with the End-Permian Mass Extinction (~96% marine species lost).

Mesozoic Era (251 - 65 Ma)

Dominance of Archosaurs and Dinosaurs across Pangaea; ends with Cretaceous-Tertiary (K-T) asteroid extinction (~65 Ma).

Cenozoic Era (65 Ma - Present)

Mammalian adaptive radiation and diversification; first ancestral hominids appear (~5 Ma).

Oxygen Revolution Evolutionary Impact

Toxic O2 forced surviving lineages to evolve aerobic respiration, yielding vastly higher ATP energy outputs.

Cambrian Arms Race Drivers

Rising O2 permitted higher metabolic rates; compound vision and active predation selected for protective shells and exoskeletons.

Land Adaptation Requirements

Adaptations to combat gravity, desiccation, and aerial respiration; amniotic eggs freed land animals from aquatic reproduction.

Biomagnification

Lipophilic, non-degradable toxins (DDT, PCBs, heavy metals) accumulate at higher concentrations at higher trophic levels.

GPP and NPP Relationship Formula

NPP = GPP - R (or GPP = NPP + R).

Gross Primary Productivity (GPP)

The total chemical energy fixed by autotrophs per unit area per unit time.

Net Primary Productivity (NPP)

The net biomass remaining after autotroph respiration (R); represents energy available to herbivores.

10% Trophic Transfer Rule

~90% of energy is lost as heat, respiration, and waste at each step; only ~10% passes to the next trophic level.

Exponential Growth (J-Curve)

Uninhibited population expansion described by P(t) = P0 · e^(rt) under ideal conditions.

Logistic Growth (S-Curve)

Population growth incorporating environmental resistance as size approaches carrying capacity (K).

r-Selected Species

Short-lived, small body size, high offspring volume, low parental investment; thrives in unstable/disturbed environments (e.g., weeds, insects).

K-Selected Species

Long-lived, large body size, few offspring, high parental investment; thrives in stable, predictable environments at carrying capacity K (e.g., elephants, whales).

Extinction Vulnerability Factors

Low reproductive rate (K-selected), specialized feeding/niche requirements, fixed migratory routes, human conflict.

Planetary Tipping Points

Thresholds where incremental environmental stresses trigger rapid, non-linear, irreversible shifts in Earth systems.

50% Ecosystem Threshold

Converting 50% to 90% of natural land cover can destabilize planetary ecosystems and trigger sudden collapse.

Stromatolites (3.5 Ga)

Layered rock structures formed by ancient cyanobacterial mats; oldest fossil evidence of terrestrial life.