Ecosystems and Global Ecology

Flashcards about Ecosystems and Global Ecology based on lecture notes.

What is an ecosystem?

Multiple communities of organisms that live in an area and their chemical and physical (abiotic) environment. It is composed of primary producers, consumers, decomposers, and the abiotic environment. Ecosystems are linked by the movement of energy and nutrients.

What limits terrestrial ecosystem productivity?

Temperature, water, and/or sunlight.

What limits marine ecosystem productivity?

Availability of nutrients.

Define Gross Primary Productivity (GPP).

The total amount of chemical energy produced in a given area and time period.

Define Net Primary Productivity (NPP).

The remaining energy (after the producer uses some to stay alive via cellular respiration) that can be put into growth and reproduction. Also known as Biomass (NPP = GPP - R).

List the four components of an ecosystem and their roles.

1. Decomposers: feed on dead organisms or their waste products.
2. Consumers: eat other living organisms.
3. Primary producers (autotrophs): synthesize their own food.
4. Abiotic environment: the soil, climate, atmosphere, and the particulate matter and solutes in water.

Define Trophic Levels.

Steps in energy transfer in an ecosystem; consist of organisms that obtain their energy from the same type of source.

What is a food chain?

Connected trophic levels in an ecosystem.

What is a food web?

A system of interlocking and interdependent food chains.

Why does productivity decline at higher trophic levels?

Inefficient energy transfer and loss of energy through respiration & other life processes. Only a fraction of the energy stored in one trophic level is transferred to the next.

What factors influence the number of trophic levels in an ecosystem?

Inefficient energy transfer, environmental stability, and environmental complexity.

What is a biogeochemical cycle?

The path an element takes as it moves between abiotic systems and organisms. Controlled by reservoirs, rates of exchange, and interactions with other cycles.

Describe the terrestrial nutrient cycle.

Nutrients cycle from organism to organism and are mostly reused.

How does water move in the global water cycle?

Ocean evaporation exceeds precipitation, precipitation falls on the continents, and water moves from the land to the oceans via streams and groundwater.

How do humans impact the global water cycle?

Humans are lowering the water table on every continent.

What are the major carbon reservoirs?

The ocean, terrestrial organisms, soil, litter, peat, and fossil fuels.

How do humans impact the global carbon cycle?

Intensive agriculture, deforestation, and the burning of fossil fuels have added large amounts of carbon dioxide to the atmosphere.

What forms of nitrogen can plants use?

Ammonium (NH4+) or nitrate (NO3-).

How is atmospheric nitrogen converted to usable forms?

Naturally converted by bacteria and lightning. Humans convert N2 to NH3 by burning fossil fuels, growing N fixing crops, and producing fertilizers.

What are the consequences of excess nitrogen in ecosystems?

"Dead zones" (too many nutrients à too many organisms that use up the local oxygen à mass mortality) and competitive exclusion (one organism uses N very well and dominates locally).

Define Biomagnification.

The increasing concentration of a substance, such as a toxic chemical, in the tissues of organisms at successively higher levels in a food chain.

What causes global warming?

Worldwide average increase in temperature due to increases in greenhouse gases.

What are the biological effects of climate change?

Geographic range shifts, phenology shifts, evolutionary adaptation, extinction, and acidification.