Key terms
131 terms- Ecosystem§56.1
- All the organisms living in a particular place plus the abiotic environment there
- Abiotic environment§56.1
- The nonliving physical and chemical surroundings of an ecosystem
- Biogeochemical cycle§56.1
- Movement of atoms of an element through organisms and geological systems
- Reservoir§56.1
- A place where a large amount of an element is stored, such as the atmosphere or ocean
- Flux§56.1
- A movement of an element from one reservoir to another, such as photosynthesis or respiration
- Carbon fixation§56.1
- Photosynthetic conversion of gaseous CO₂ into nongaseous organic compounds
- Carbon dioxide (CO₂)§56.1
- Most significant abiotic carbon compound; 0.03% of atmospheric volume
- Bicarbonate (HCO₃⁻)§56.1
- Ion formed when CO₂ reacts spontaneously with water; a carbon source for aquatic photosynthesis
- Organic carbon§56.1
- Carbon molecules occurring within an organism
- Methanogen§56.1
- Microbe that breaks down organic matter by anaerobic respiration and releases CH₄
- Methane (CH₄)§56.1
- Anaerobic breakdown product; oxidized abiotically to CO₂ in the atmosphere
- Fossil fuels§56.1
- Coal, petroleum, and natural gas formed from organic matter buried over geologic time
- Water cycle§56.1
- Circulation of water among atmosphere, land, oceans, and organisms
- Evaporation§56.1
- Change of liquid water to vapor, requiring a large input of thermal energy
- Transpiration§56.1
- Evaporation of water from leaves and other plant surfaces after root uptake
- Precipitation§56.1
- Fall of water droplets or crystals as rain or snow once they grow large enough
- Percolation§56.1
- Downward seepage of water through soil that recharges groundwater
- Groundwater§56.1
- Water under the ground; over 95% of all freshwater in the United States
- Aquifer§56.1
- Permeable underground layer of rock, sand, and gravel often saturated with water
- Water table§56.1
- Upper unconfined groundwater layers that feed streams and are partly reachable by roots
- Ogallala Aquifer§56.1
- Deep Great Plains aquifer being depleted faster than it is recharged
- Nitrogen (N₂)§56.1
- Elemental atmospheric nitrogen, 78% of air by volume, unusable by plants and animals
- Ammonia (NH₃)§56.1
- Nitrogen form usable by plants and algae; also the main animal nitrogen waste
- Ammonium (NH₄⁺)§56.1
- Fixed nitrogen salt manufactured industrially from N₂ for fertilizer
- Nitrate (NO₃⁻)§56.1
- Oxidized nitrogen form usable by plants and algae; the ion tracked at Hubbard Brook
- Nitrogen fixation§56.1
- Synthesis of nitrogen compounds from N₂; strictly, the step N₂ → NH₃
- Nitrogenase complex§56.1
- Enzyme system (nif gene complex) certain prokaryotes use to fix nitrogen
- Nitrification§56.1
- Prokaryotic oxidation of part of the NH₃ to form NO₃⁻
- Ammonification§56.1
- Microbial conversion of organic nitrogen wastes such as urea back to NH₃
- Denitrification§56.1
- Prokaryotic conversion of NO₃⁻ nitrogen into N₂ or other nitrogen gases such as N₂O
- Symbiotic nitrogen fixers§56.1
- Fixing microbes living in the roots of legumes, alders, myrtles, and similar plants
- Legumes (Fabaceae)§56.1
- The pea family, the classic host of root-symbiotic nitrogen-fixing microbes
- Urea§56.1
- Nitrogen waste excreted in mammalian urine; microbes convert it back to NH₃
- Phosphate (PO₄³⁻)§56.1
- The single oxidation state in which phosphorus exists in ecosystems
- Phosphate remineralization§56.1
- Decay microbes releasing inorganic PO₄³⁻ from dead organic matter for reuse
- Weathering§56.1
- Breakdown of rock that releases new phosphate into terrestrial systems
- Limiting nutrient§56.1
- The element in shortest supply relative to the needs of plants and algae
- Iron limitation§56.1
- Iron limits phytoplankton in about one-third of the oceans, supplied by wind-borne dust
- Saharan dust§56.1
- Iron-rich dust blown west on the Trade Winds that fertilizes distant ocean waters
- Eutrophication§56.1
- Explosive growth of formerly nutrient-limited species after nutrient enrichment
- Hubbard Brook Experimental Forest§56.1
- New Hampshire watershed study of nutrient cycling in a temperate deciduous forest
- Deforestation experiment§56.1
- One of six Hubbard Brook valleys clear-cut in 1965–1966 with regrowth prevented
- Nitrate runoff§56.1
- Nitrate lost in stream water; went from +5 to −53 kg per hectare per year after clearing
- Algal bloom§56.1
- Downstream explosion of algae fueled by nitrate lost from the deforested valley
- Energy flow§56.2
- One-way passage of energy through an ecosystem, ending as heat radiated to space
- Open system (energy)§56.2
- Earth with respect to energy: sunlight in, infrared heat out
- First Law of Thermodynamics§56.2
- Energy is neither created nor destroyed but frequently changes form
- Second Law of Thermodynamics§56.2
- Entropy tends to increase, so some energy is inevitably converted to heat
- Chemical-bond energy§56.2
- The form of energy animals must obtain, stored in the bonds of food molecules
- Heat§56.2
- The degraded end form of energy that no organism can use as an energy source
- Greenhouse effect§56.2
- Atmospheric changes that impede outgoing radiation and raise global temperature
- Autotroph§56.2
- Organism that builds organic compounds from inorganic precursors using abiotic energy
- Photoautotroph§56.2
- Autotroph using light energy: plants, algae, cyanobacteria
- Chemoautotroph§56.2
- Autotroph using inorganic oxidation reactions; all are prokaryotic
- Heterotroph§56.2
- Organism that must take in organic compounds made by other organisms
- Food chain§56.2
- Sequence of species that eat one another in order, such as plants → insect → shrew → hawk
- Food web§56.2
- The realistic branching network formed because species feed at multiple trophic levels
- Trophic level§56.2
- A feeding level used to organize who eats whom in an ecosystem
- Primary producers§56.2
- Trophic level 1 — all the autotrophs in the system
- Consumers§56.2
- The heterotrophs occupying every trophic level above the primary producers
- Herbivores§56.2
- Trophic level 2 — heterotrophs feeding directly on primary producers
- Primary carnivores§56.2
- Trophic level 3 — heterotrophs that eat or parasitize herbivores
- Secondary carnivores§56.2
- Trophic level 4 — heterotrophs that feed on primary carnivores
- Omnivore§56.2
- Animal that eats both primary producers and other animals
- Detritivore§56.2
- Trophic level feeding on the remains of already dead organisms
- Detritus§56.2
- Dead organic matter
- Decomposers§56.2
- Subcategory of detritivores — microbes and minute organisms that break up dead matter
- Productivity§56.2
- Rate at which a trophic level collectively synthesizes new organic matter
- Primary productivity§56.2
- The productivity of the primary producers
- Gross primary productivity (GPP)§56.2
- The raw rate at which primary producers synthesize new organic matter
- Net primary productivity (NPP)§56.2
- GPP minus producer respiration — the organic matter available to herbivores
- Secondary productivity§56.2
- The productivity of any heterotroph trophic level
- One percent rule§56.2
- Producers capture about 1% of the solar energy impinging on an ecosystem
- Ten percent rule§56.2
- Energy available to a trophic level is about 10% of that available to the level below
- Biome§56.2
- A general ecosystem type such as tropical rainforest, savanna, or desert
- World NPP§56.2
- Productivity per square meter multiplied by the world area that ecosystem type covers
- Cayuga Lake study§56.2
- Energy accounting showing 1000 cal of algae yields 6 cal to smelt-eaters, 1.2 to trout-eaters
- Ecological pyramid§56.2
- Stacked boxes whose widths show an ecological property across trophic levels
- Pyramid of energy flow§56.2
- Ecological pyramid based on productivity; always upright
- Standing crop biomass§56.2
- The biomass of all individuals alive at the same time
- Pyramid of biomass§56.2
- Ecological pyramid based on standing crop biomass; usually but not always upright
- Inverted pyramid of biomass§56.2
- Pyramid in which a level holds more biomass than the level below it
- Pyramid of numbers§56.2
- Ecological pyramid based on counts of individuals; usually upright
- Phytoplankton§56.2
- Single-celled algae whose rapid turnover permits an inverted biomass pyramid
- Trophic cascade§56.3
- Effects exerted at an upper trophic level flowing down through two or more lower levels
- Top-down effect§56.3
- An effect exerted from an upper trophic level downward
- Bottom-up effect§56.3
- An effect flowing up the chain from primary producers to higher trophic levels
- Brown trout experiment§56.3
- New Zealand three-level study: trout cut invertebrates by a third and raised algae fivefold
- Damselfly nymph experiment§56.3
- Northern California four-level study: fish cut nymphs, raised insects, lowered algae
- Sea otter cascade§56.3
- Otters eat urchins, urchins eat young kelp; otter abundance controls kelp forest development
- Sea urchin§56.3
- Grazer that suppresses kelp forests when released from otter predation
- Kelp forest§56.3
- Algal forest that flourishes when otters keep urchin numbers low
- Orca predation§56.3
- Recent killer whale switch to eating otters, pushing the kelp system toward the urchin state
- Keystone species§56.3
- A species whose loss reshapes the whole community, as the otter does for kelp forests
- Aldo Leopold§56.3
- Naturalist who described wolfless mountains browsed bare, anticipating trophic cascades
- Barro Colorado Island§56.3
- Panama Canal island that lost large predators; at least 15 bird species then vanished
- Mesopredator increase§56.3
- Explosion of monkeys, peccaries, coatimundis, and armadillos after top predators are lost
- Overfishing cascade§56.3
- Billfish and cod cut to about 10% of former numbers, releasing their shrimp and crab prey
- Eel River experiment§56.3
- Roofed river enclosures varying light to test bottom-up predictions
- Species richness§56.4
- The number of species present in a community
- Ecosystem stability§56.4
- Remaining relatively constant in composition and resisting disturbance
- Invasibility§56.4
- The ease with which nonnative species establish in a community; a measure of stability
- Cedar Creek Natural History Area§56.4
- Minnesota site where 207 prairie plots were monitored for 11 years
- Nitrogen uptake study§56.4
- Cedar Creek study of 147 plots linking more species to more uptake and more biomass
- Sampling objection§56.4
- Criticism that richer plots simply have a better chance of containing one productive species
- Overyielding§56.4
- Plot productivity exceeding that of the single most productive species grown in isolation
- Hump-shaped curve§56.4
- Species richness peaking at intermediate productivity rather than rising steadily
- Habitat heterogeneity§56.4
- Spatial variation in the abiotic environment providing many habitat types
- Structural complexity§56.4
- Plant architecture variation that predicts desert lizard species richness
- Climatic stability§56.4
- Low temperature variation, correlated with higher mammal species richness
- Species diversity gradient§56.4
- Steady increase in species richness from the Arctic to the tropics
- Evolutionary age hypothesis§56.4
- Idea that long uninterrupted tropical history allowed more diversification
- Glacial refuges§56.4
- Small areas to which tropical forest contracted during glaciations, shown by pollen cores
- Productivity hypothesis§56.4
- Idea that greater tropical sunlight and year-round growth support more species
- Stability hypothesis§56.4
- Idea that reduced tropical seasonality allows more, narrower niches; best supported
- Predation hypothesis§56.4
- Idea that intense tropical predation reduces competition and permits niche overlap
- Spatial heterogeneity hypothesis§56.4
- Idea that structurally complex tropical forests create many microhabitats
- Island biogeography§56.5
- Study of the patterns and causes of species richness on islands
- Species-area relationship§56.5
- The observation that larger islands contain more species than smaller ones
- MacArthur and Wilson§56.5
- Authors of the 1967 equilibrium model of island biogeography
- Equilibrium model§56.5
- Island richness as a dynamic balance between colonization and extinction
- Colonization rate§56.5
- Arrival rate of new species; falls as the pool of absent species is depleted
- Extinction rate§56.5
- Loss rate of resident species; rises as more species are present
- Equilibrium number of species§56.5
- The species number at which colonization and extinction rates are equal
- Area effect§56.5
- Smaller islands have higher extinction rates, shifting equilibrium to fewer species
- Distance effect§56.5
- More distant islands have lower colonization rates, again shifting equilibrium left
- Species turnover§56.5
- Ongoing replacement of species at equilibrium; observed to be lower than predicted
- Simberloff and Wilson experiment§56.5
- Florida Keys mangrove islands censused, fumigated, and monitored during recolonization
- Adaptive radiation§56.5
- One ancestral species giving rise to many descendants each in a different niche
- Allopatric speciation§56.5
- Speciation after a population is split by a barrier such as a river
- Character displacement§56.5
- Evolution of differences between species that allows them to coexist