Flows of energy and matter

Energy cannot be created or destroyed; it can only be transformed from one form to another.

An open system exchanges both energy and matter with its surroundings.

Energy does not cycle; it flows through ecosystems and is lost as heat.

Main input is sunlight; main output is heat.

Every energy transfer is inefficient; some energy is dissipated as heat, so less usable energy remains.

Energy cannot be created or destroyed, only transformed.

Energy transfers are inefficient and some energy becomes heat.

Energy is used for respiration, movement and maintenance and much is lost as heat, so only a small proportion becomes new biomass.

Energy flows through ecosystems and is eventually lost as heat, so it cannot be recycled.

Use “energy is transformed” for the first law and “transfers are inefficient with heat loss” for the second law.

Sunlight is captured by producers, transferred by feeding through consumers, and leaves the system as heat at each step.

An open system exchanges energy and matter with its surroundings.

Heat loss at each transfer reduces usable energy at higher trophic levels, limiting the number of trophic levels supported.

Energy is lost as heat at each transfer so less usable energy remains to build biomass at higher levels.

Fewer energy transfers means less heat loss, so more of the original energy supports food production.

Energy efficiency is the percentage of energy transferred from one trophic level to the next.

Photosynthesis.

Photosynthesis is the conversion of light energy into chemical energy stored in glucose.

Energy is lost as heat from respiration and in waste/uneaten material (faeces, bones, plant fibre).

Cellular respiration is the process that releases energy from glucose in cells, usually using oxygen.

Incomplete consumption is when not all parts of an organism are eaten, so energy in those parts is not transferred.

Cellular respiration.

On average, about 10% of energy at one trophic level becomes biomass available to the next level.

Inputs: carbon dioxide and water. Outputs: glucose and oxygen.

Some energy is transferred to ATP for life processes and a significant amount is released as heat.

Inefficient digestion is when not all ingested food is absorbed; energy leaves the body as faeces.

Heat loss from respiration and losses in waste/uneaten material.

Photosynthesis occurs in chloroplasts.

Yes. Plants respire continuously to release energy for life processes.

Energy is used for respiration, movement and maintenance and is lost as heat and waste rather than becoming new biomass.

Organisms use energy for metabolism and release much of it as heat, so less becomes new biomass available to the next level.

About 10% (order-of-magnitude).

Energy leaves mainly as heat released during respiration.

It traps solar energy and stores it as chemical energy in biomass that can be transferred through food chains.

Low transfer efficiency leaves too little energy at higher trophic levels to support many levels, so chains are short.

Because only a small proportion of energy becomes new biomass at each trophic transfer; most is lost as heat and waste.

Respiration releases heat, showing that energy transfers are inefficient and usable energy decreases.

Less energy becomes new biomass at each transfer because most is lost as heat and waste, so biomass decreases at higher levels.

Fewer trophic transfers means less energy is lost as heat before reaching humans.

Energy enters mainly as sunlight and is captured by producers via photosynthesis.

Ecological pyramids are diagrams that represent trophic levels using numbers, biomass, or energy, with producers at the base.

Biomass is the total dry mass of living organisms in a given area, representing stored chemical energy at a trophic level.

A pyramid of numbers shows the number of individual organisms at each trophic level.

A pyramid of biomass shows the total dry mass of organisms at each trophic level.

A pyramid of energy shows energy flow per unit area per unit time at each trophic level.

Energy is lost as heat at every trophic transfer, so less energy is available at higher levels.

One large producer, such as a tree, can support many consumers like insects, making the level above wider.

Producers capture incoming energy, usually sunlight, and convert it into biomass that supports all higher trophic levels.

Water content varies widely and does not contain usable chemical energy, so drying allows fair comparison of stored energy between organisms and trophic levels.

Producers like phytoplankton have low standing biomass but reproduce rapidly, supporting larger consumer biomass.

They show that numbers, biomass, and available energy usually decrease at higher trophic levels.

Productivity measures a rate: how quickly new biomass is produced.

Productivity is the rate at which new biomass is produced in an ecosystem.

Productivity is the rate at which new biomass is produced in an ecosystem, usually by producers through photosynthesis.

Gross productivity is total energy captured; net productivity is what remains after respiration losses.

Gross productivity is the total biomass or energy gained by producers through photosynthesis before losses to respiration.

Net productivity equals gross productivity minus respiration: NP = GP − R.

Net productivity is the biomass or energy remaining after respiration losses, available for growth, reproduction, and transfer to the next trophic level.

NP = GP − R.

Net productivity equals gross productivity minus respiration: NP = GP − R.

Respiration represents energy used by organisms for metabolism and life processes, released mainly as heat.

Net productivity is available to consumers because it is the biomass remaining after producers use energy for respiration.

Energy is lost as heat through respiration at each transfer, so less energy remains to form new biomass at higher levels.

Producers such as plants and algae are responsible for most productivity because they convert sunlight into chemical energy through photosynthesis.

Productivity measures how quickly new biomass is produced over time, not the total amount present.

Energy used in respiration is released as heat to the environment and cannot be passed to the next trophic level.

Net productivity is transferred because it represents biomass remaining after respiration.

Energy is lost at each trophic transfer, so progressively less energy is available to support higher trophic levels.

More energy is used for life processes and released as heat, leaving less energy available to form new biomass.

High light availability, suitable temperature, and sufficient nutrients can all increase productivity.