Food chain / web

Synthesise organic compounds from atmospheric or aquatic CO2 using light energy

Obtain energy from consuming other organisms (Animals)

Decomposers that recycle nutrients back into the ecosystem

Each stage in a food chain or web

Energy transfer

Total mass of living material in a given area Available for consumption and energy transfer through an ecosystem

Measured as mass of carbon or dry mass of tissue per given area

The water content of living tissue can vary, so dry mass is a more reliable measure

Units for dry mass are mass per unit area, e.g. kg m^-2

Requires dry mass Heat in an oven around 100 °C to evaporate water Record mass and reheat continually until constant mass achieved Water content can vary in fresh mass

It can take a long time to fully dehydrate a plant sample to find its dry mass; the drying process could take several days for larger samples Precise equipment may not be available in a school laboratory A very precise digital balance should be used to detect extremely small changes in mass

use a measuring cylinder to measure a set volume of water into a copper beaker record the mass of the water record the starting temperature of the water using a thermometer record the starting mass of the dry sample place the sample in a crucible and place beneath the beaker of water set fire to the sample and allow it to burn until it has completely burned away record the final temperature of the water calculate the change in temperature of the water calculate the energy transferred per gram of the dry sample as follows: Q = MC/\T where m is mass of water then divide it by however many grams of sample you used so its joules per gram

Pyramid of energy as it shows total amount of energy stored in the biomass of organisms at each trophic level More accurate as two organisms can have identical biomasses but different energy stores

The area/volume of each organism