Ecosystems | Quizlet

What are the major abiotic factors affecting life?

Temperature, water and oxygen, sunlight, salinity, and soil.

What primarily determines terrestrial biome distribution?

The combination of temperature and precipitation.

How does increasing latitude generally affect climate and biomes?

Temperature generally decreases as you move away from the equator, producing shifts toward colder biomes.

How can increasing elevation resemble increasing latitude?

Both generally produce colder conditions and can cause similar changes in biome type.

What is a biome?

A large ecological region characterized primarily by climate and its dominant vegetation.

What characterizes a tropical rainforest?

Warm temperatures, high precipitation, high productivity, and high biodiversity.

What characterizes a savanna?

Warm climate with distinct wet and dry seasons, dominated by grasses with scattered trees.

What defines a desert?

Very low precipitation; deserts can be hot or cold.

What characterizes a temperate grassland?

Seasonal temperatures, moderate precipitation, and vegetation dominated by grasses.

What characterizes taiga/boreal forest?

Cold conditions, coniferous vegetation, and a relatively short growing season.

What characterizes tundra?

Very cold conditions, low precipitation, and a very short growing season.

What is primary productivity?

The rate at which primary producers capture energy and produce organic material.

How do temperature and precipitation generally affect terrestrial productivity?

Warm, wet environments generally support greater productivity than cold or dry environments.

What is the photic zone?

The region of water receiving enough light to support photosynthesis.

What is the aphotic zone?

The region where insufficient light is available for photosynthesis.

What is the pelagic zone?

The open-water portion of an aquatic ecosystem.

What is the benthic zone?

The bottom substrate of an aquatic ecosystem.

What is the intertidal zone?

The coastal area periodically submerged and exposed by tides.

What is thermal stratification?

The formation of water layers with different temperatures and densities, which can reduce mixing.

Why is thermal stratification ecologically important?

It affects mixing and therefore the distribution of nutrients and oxygen within a body of water.

What is upwelling?

The movement of nutrient-rich deep water toward the surface.

Why does upwelling increase productivity?

It supplies nutrients to producers in surface waters where light is available for photosynthesis.

How are energy and nutrients different in ecosystems?

Energy flows through ecosystems and is eventually lost as heat, while nutrients are recycled through biogeochemical cycles.

What are primary producers?

Autotrophs that capture energy and form the base of trophic systems.

What is a trophic level?

A feeding position within a food chain or food web.

Approximately how much energy passes from one trophic level to the next?

About 10%.

Approximately how much energy is lost between trophic levels?

About 90%, much of it dissipated as heat through metabolism.

Why are food chains limited in length?

Energy decreases dramatically at each trophic transfer, eventually leaving too little energy to support another level.

Can an energy pyramid be inverted?

No. Energy decreases at every trophic transfer, so energy pyramids are always upright.

Can biomass or pyramids of numbers sometimes be inverted?

Yes. Unlike energy pyramids, biomass or numbers may sometimes be greater at a higher trophic level than at the level below.

What is a limiting nutrient?

An essential nutrient that is in short supply relative to biological demand and therefore limits productivity.

What is nitrogen fixation?

Conversion of atmospheric nitrogen gas into biologically usable forms of nitrogen.

Why can nitrogen be limiting even though the atmosphere contains abundant N2?

Most organisms cannot directly use atmospheric nitrogen gas and depend on nitrogen fixation to produce usable forms.

What is the major distinguishing feature of the phosphorus cycle?

Phosphorus does not have a major atmospheric phase and is largely released through weathering of rocks.

What major processes move carbon between organisms and the environment?

Photosynthesis incorporates carbon dioxide into organic matter, while respiration returns carbon dioxide to the environment.

What is a top-down effect?

A change at a higher trophic level affects organisms at lower trophic levels.

What is a bottom-up effect?

A change in resources or primary producers affects organisms at higher trophic levels.

A predator population decreases. What would you predict for herbivores and vegetation?

Herbivores would tend to increase and vegetation would tend to decrease; this is a top-down effect.

What is a trophic cascade?

Indirect effects across multiple trophic levels caused by a change at one trophic level.

If primary producer abundance increases and higher trophic levels subsequently increase, what type of effect is occurring?

A bottom-up effect.

What is species richness?

The number of different species present in an ecosystem or community.

How can greater species richness affect ecosystem stability?

Greater species richness may increase stability and resistance to environmental changes or disturbances.

Where is species diversity generally greatest?

Tropical regions near the equator.

What happens to species diversity as latitude increases away from the equator?

It generally decreases.

What does the equilibrium model of island biogeography describe?

Island species richness as a balance between colonization and extinction.

Why do larger islands generally contain more species?

They provide more habitat and populations are generally less vulnerable to extinction.

Why do islands near a mainland generally contain more species than distant islands?

Nearby islands have higher rates of colonization.

Which island should generally have the greatest species richness: large/near or small/far?

A large island near the mainland.

Which island should generally have the lowest species richness: large/near or small/far?

A small island far from the mainland.

A region becomes warmer and wetter. What ecological change might you predict?

Primary productivity may increase because temperature and water availability strongly influence plant growth.

Deep nutrient-rich water rises into a sunlit ocean region. What should happen to primary productivity?

It should increase because upwelling supplies nutrients to photosynthetic producers.

Why can a change in predators ultimately affect primary producers?

Predators regulate consumers such as herbivores, so changing predator abundance can indirectly change plant abundance through a trophic cascade.

What is the single most important difference between energy flow and biogeochemical cycling?

Energy moves through trophic levels and is lost as heat, whereas matter such as carbon, nitrogen, phosphorus, and water is recycled.