Unit 1 · The Living World: Ecosystems

Predator-prey relationship ● (core concept) — In a predator-prey relationship, the predator is an organism that eats another organism (the prey).

Symbiosis ● (core concept) — Symbiosis is a close and long-term interaction between two species in an ecosystem. The three types are mutualism, commensalism, and parasitism.

Mutualism ● (core concept) — A type of symbiosis in which both species involved benefit from the interaction.

Commensalism ● (core concept) — A type of symbiosis in which one species benefits and the other is neither helped nor harmed.

Parasitism ● (core concept) — A type of symbiosis in which one species benefits at the expense of the other (the host).

Competition ● (core concept) — Competition can occur within a species (intraspecific) or between species (interspecific) where resources are limited.

Resource partitioning ● (core concept) — Using resources in different ways, places, or at different times, which can reduce the negative impact of competition on survival.

Biome ● (core concept) — A biome contains characteristic communities of plants and animals that result from, and are adapted to, its climate.

Major terrestrial biomes ● (core concept) — The major terrestrial biomes are taiga, temperate rainforests, temperate seasonal forests, tropical rainforests, shrubland, temperate grassland, savanna, desert, and tundra.

Distribution of terrestrial resources ● (core concept) — The global distribution of nonmineral terrestrial resources such as water and lumber trees varies because of some combination of climate, geography, latitude and altitude, nutrient availability, and soil.

Biome shifts ● (core concept) — The worldwide distribution of biomes is dynamic; it has changed in the past and may shift again as a result of global climate changes.

Freshwater biomes ● (core concept) — Freshwater biomes include streams, rivers, ponds, and lakes. These freshwater biomes are a vital resource for drinking water.

Marine biomes ● (core concept) — Marine biomes include oceans, coral reefs, marshland, and estuaries. Algae in marine biomes supply a large portion of the Earth's oxygen and also take in carbon dioxide from the atmosphere.

Distribution of marine resources ● (core concept) — The global distribution of nonmineral marine resources such as fish varies because of some combination of salinity, depth, turbidity, nutrient availability, and temperature.

Carbon cycle ● (core concept) — The carbon cycle is the movement of atoms and molecules containing the element carbon between sources and sinks.

Carbon sources and sinks ● (core concept) — A source is a process or location that releases carbon; a sink (reservoir) stores it. Some reservoirs hold carbon compounds for long periods of time, while others hold them for relatively short periods.

Photosynthesis and respiration ● (core concept) — Carbon cycles between photosynthesis and cellular respiration in living things: photosynthesis removes carbon dioxide from the atmosphere, while respiration releases it back.

Fossil fuel carbon release ● (core concept) — Plant and animal decomposition led to the storage of carbon over millions of years as fossil fuels. Burning fossil fuels quickly moves that stored carbon into the atmosphere as carbon dioxide.

Nitrogen cycle ● (core concept) — The nitrogen cycle is the movement of atoms and molecules containing the element nitrogen between sources and sinks. Its steps include nitrogen fixation, assimilation, ammonification, nitrification, and denitrification, and microorganisms in the soil play an important role in many of them.

Nitrogen fixation ● (core concept) — In nitrogen fixation, atmospheric nitrogen (N2) is converted by certain types of soil bacteria into ammonia (NH3). In the soil, ammonia quickly converts to ammonium (NH4+), which is available for biological uptake.

Nitrogen limitation ● (core concept) — The availability of nitrogen compounds in the soil is limited by the rate of nitrogen fixation. In many ecosystems, nitrogen availability limits primary production by plants and other producers.

Atmospheric nitrogen reservoir ● (core concept) — The largest reservoir of nitrogen is the atmosphere. Most of the reservoirs in which nitrogen compounds occur hold those compounds for relatively short periods of time.

Phosphorus cycle ● (core concept) — The phosphorus cycle is the movement of atoms and molecules containing the element phosphorus between sources and sinks. Unlike the other cycles, it lacks a significant atmospheric component.

Phosphorus reservoirs ● (core concept) — The major reservoirs of phosphorus are rock and ocean sediments containing phosphorus-bearing minerals. Phosphorus-bearing minerals are released as rocks weather.

Phosphorus as a limiting nutrient ● (core concept) — Phosphorus is relatively scarce in ecosystems because rocks weather slowly, so it is often a limiting nutrient for plants and other producers, particularly in freshwater and some terrestrial ecosystems.

Hydrologic (water) cycle ● (core concept) — The hydrologic cycle, which is powered by the sun, is the movement of water in its various solid, liquid, and gaseous phases between sources and sinks.

Ocean water reservoir ● (core concept) — The oceans are the primary reservoir of water at the Earth's surface, with ice caps and groundwater acting as much smaller reservoirs.

Primary productivity ● (core concept) — Primary productivity is the rate at which solar energy (sunlight) is converted into organic compounds via photosynthesis over a unit of time.

Gross primary productivity (GPP) ● (core concept) — Gross primary productivity is the total rate of photosynthesis in a given area.

Net primary productivity (NPP) ● (core concept) — Net primary productivity is the rate of energy storage by photosynthesizers in a given area, after subtracting the energy lost to respiration.

Units of productivity ● (core concept) — Productivity is measured in units of energy per unit area per unit time, for example kcal/m2/yr.

Light and aquatic photosynthesis ● (core concept) — Most red light is absorbed in the upper 1 m of water, and blue light only penetrates deeper than 100 m in the clearest water. This affects photosynthesis in aquatic ecosystems, whose photosynthesizers have adapted to the lack of visible light at depth.

Energy inflow requirement ● (core concept) — All ecosystems depend on a continuous inflow of high-quality energy in order to maintain their structure and function of transferring matter between the environment and organisms via biogeochemical cycles.

Conservation of matter ● (core concept) — Biogeochemical cycles are essential for life, and each cycle demonstrates the conservation of matter: matter is neither created nor destroyed as it cycles.

Direction of energy flow ● (core concept) — In terrestrial and near-surface marine communities, energy flows from the sun to producers in the lowest trophic levels and then upward to higher trophic levels.

10% rule ● (core concept) — The 10% rule approximates that in the transfer of energy from one trophic level to the next, only about 10% of the energy is passed on.

Thermodynamics and energy loss ● (core concept) — The loss of energy that occurs when energy moves from lower to higher trophic levels can be explained through the laws of thermodynamics.

Food chain ● (core concept) — A food chain depicts the flow of energy and matter from producers (autotrophs) to primary consumers (herbivores) and secondary and tertiary consumers (omnivores and carnivores).

Food web ● (core concept) — A food web is a model of an interlocking pattern of food chains that depicts the flow of energy and matter in two or more food chains.

Detritivores and decomposers ● (core concept) — Detritivores and decomposers play an essential role in food chains and food webs by returning nutrients to the soil.

Feedback loops in food webs ● (core concept) — Positive and negative feedback loops can each play a role in food webs: when one species is removed from or added to a food web, the rest of the food web can be affected.