13- food webs and energy flow

Flashcards based on lecture notes about Ecosystems.

What is the focus of study for ecosystem scientists?

interactions among biotic and abiotic components, processes, like energy flow and nutrient cycling, and ecosystem stability & its responses to disturbance.

Is Earth an open or closed system in terms of energy?

Earth is an open system in terms of energy. Energy flows in as sunlight and out as heat

Is Earth an open or closed system in terms of matter?

Earth is a closed system in terms of matter, where matter is recycled.

What is the sequence of energy flow in an ecosystem?

Solar Energy -> Producer (autotrophs) -> Consumer (herbivores) -> Consumer (carnivores) -> Decomposers.

What is an autotroph, and what are they also known as?

makes own food

• Primary producer or producer.

What is a heterotroph, and what are they also known as?

consumes food

• Secondary producer or consumer.

What is photosynthesis?

Energy from the sun (radiant energy) is captured by autotrophs and transformed into chemical energy of sugar molecules

What is Gross Primary Productivity (GPP)?

GPP is the total rate of photosynthesis or total energy assimilation by autotrophs.

what does cellular respiration do?

makes ATP and turns the glucose back into carbon dioxide, which is used in photosynthesis

What is Net Primary Productivity (NPP)?

NPP is the total rate of energy storage as organic matter, representing the total amount of biomass produced

what is the equation for NPP?

NPP = GPP – R

what is biomass?

the amount of organic material or tissue present; represents the amount of energy available to consumers

how much sunlight do producers absorb a year?

only 1%

What are the limitations to NPP?

Climate (temperature, precipitation), and nutrients (nitrogen, phosphorus, etc.).

what is NOT a limitation of growth for producers>

energy from the sun

What two factors are the biggest drivers of NPP?

Temperature and precipitation.

Where is NPP highest in oceans?

Shallow waters around continents due to higher nutrient availability.

what is the Light compensation point?

depth of water or level of light at which photosynthesis and respiration balance each other

What is the photic zone?

Zone of water above the light compensation point, where photosynthesis and respiration balance each other.

where are producers restricted to in the ocean?

photic zone

where are nutrients highest in when referring to aquatic systems, and why?

highest in shallow waters

• Greater mixing with bottom sediments

• Inputs from terrestrial systems

what determins the nutrient availability in the photic zone?

the interaction between Abiotic and biotic factors

why predicting NPP in freshwater systems more complex?

light, plant community, and nutrient inputs vary across systems

What is a trophic level?

Each link in a food chain where energy from food passes from one organism to another.

What percentage of energy is typically passed on to the next trophic level?

About 10% of the energy is passed on to the next trophic level.

What is secondary productivity?

The formation of living biomass of heterotrophic organisms.

What is Assimilation Efficiency?

A/I *100

• Assimilation (A): the portion of food used by the body (I - W)

• Ingestion (I): what you eat.

• Egestion (W): What you excrete as waste.

What is Production Efficiency?

P/A * 100

• Production (P): secondary production

• Respiration (R): the portion of food used by the body.

how do consumers vary in efficiency of secondary production in terms of Assimilation Efficiency?

• Endotherms more efficient than ectotherms

• Carnivores more efficient than herbivores

how do consumers vary in efficiency of secondary production in terms of production efficiency?

• Ectotherms more efficient than endotherms

• Invertebrates more efficient than vertebrates

• Large animals more efficient than small

what are ecological pyramids?

diagram that shows amount of energy in different trophic levels in ecosystem

How much NPP is consumed by decomposers?

Large majority of NPP (90-96%) is consumed by decomposers.

What is the rule of thumb for energy loss between trophic levels?

90% of energy is lost from one trophic level to the next.

what do food webs include?

Grazing and Detrital Food Chains

what are the three types of ecological pyramids?

number, biomass, and energy