lecture 7: ecosystems and energy flows

Photosynthesis

The process by which plants, algae, and some bacteria convert sunlight, CO₂, and water into chemical energy (glucose) and oxygen.

Respiration

The process by which organisms break down organic molecules to release energy (ATP), producing CO₂ and water as byproducts.

Gross Primary Productivity (GPP)

all the energy obtained from sunlight by autotrophic organisms

Net Primary Production (NPP)

all the energy available to other organisms from autotrophs

Net Primary Productivity (NPP)

The energy remaining after primary producers use some for respiration (NPP = GPP - R). This energy is available to consumers in the ecosystem.

NPP Equation and units

NPP = GPP - R (biomass/unit area/time)

Respiration

the energy used directly for metabolism

2 Things that Limit Terrestrial NPP

water and extreme temperatures

why does water limit productivity

plants lost water in exchange for gaining carbon in photosynthesis

why do extreme temperatures limit productivity

photosynthetic enzymes are temp sensitive

5 Trophic levels

primary producers, herbivores, primary carnivores, secondary carnivores, detritivores

detritivores

eat dead tissues and organisms

energy flow

The movement of energy through an ecosystem, from sunlight to producers to consumers, with losses at each trophic level.

ecological efficiency

the percentage of energy transferred from one trophic level to the next, typically around 10% due to energy lost as heat and respiration.

assimilation fraction

fraction of energy used by organism for growth and respiration

trophic pyramid

A graphical representation of energy flow in an ecosystem, showing the decrease in energy at higher trophic levels.

top-down control

When predators regulate ecosystem structure by controlling the population of herbivores and producers.

bottom-up control

produces are most limiting resource for everything else

sociometabolism

metabolism of humans accounting for bodily energy use (metabolism) and also indirect consumption

Equation for NPP

NPP = GPP - R (Net Primary Productivity is what remains after respiration).

ecological efficiency equation

(energy available to next trophic level) / (energy consumed) * 100%.

assimilation fraction equation

(energy used for growth and respiration) / (energy consumed)

fossil fuels

dead plants (biomass) produced by long time photosynthesis