Pyramids of Biomass.

https://www.revisely.com/gcse/biology/aqa/video/SK6

Whats biomass

We can measure the mass of all of the organisms at a certain trophic level, this is called biomass.

What would a scientist do to work out the biomass of a caterpillar in a food chain.

They would collect all catterpillars in an area and kill them . they would then dry them and weigh them. This gives us the dry biomass.

Dry biomass is more useful than wet biomass, this is because the moisture content of organisms can vary widely and produce inaccurate results.

Instead of killing , they could just look up data in scientific journal.

What does a pyramid of biomass look like

Trophic level 1 are producers, theyre plants or algae that use light energy to carry out photosynthesis.

Why does amount of biomass decrease in each trophic level

Biomass is the living tissue of an organisms including proteins, lipids and carbohydrates.

Imagine a bird eats 10g of biomass of a caterpillar, only 10% of biomass of caterpillar ends up in bird, so 1g. This is because not all of the material that bird ingests is absorbed, some is released as faeces.

Some of the biomass that is absorbed is converted into waste products of metabolism and is released e.g urea in humans.

A large amount of biomass is used by the bird for respiration to release energy, aerobic resp also produces co2 and water, so biomass is used to produce these waste compounds. Energy from resp is used for movement, and to keep constant body temp in mammals.

Why do food chains have low trophic levels

Only 10% of biomass passes onto next trophic level, This is more realistic diagram

In the course of a month, a cow consumes 300kg of grass biomass and gains 15kg of body mass. Calculate efficiency of biomass transfer.

Efficiency = 15 / 300. = 0.05 × 100 = 5%

How do we work out efficiency

Gain in Biomass / Total biomass intake.