23.2 - Biomass Transfer

Question 1

What is a trophic level?

Answer 1

Each stage in a food chain

Question 2

What are producers?

Answer 2

• First trophic chain
• Convert sunlight into energy

Everything else is a consumer

Question 3

Define biomass

Answer 3

The mass of living material present in a particular place or in organisms.

Question 4

How to measure biomass?

Answer 4

At trophic levels:
- Multiply biomass by total no of organisms in trophic level

Easy way:

• Measure mass of fresh material without water
• Organisms are killed to be dried
• placed in oven at 80 degrees for all water to evaporate (2 identical mass readings)
• small sample taken, may not be representative
• measured in gm-2 or gm-3

Question 5

Describe the efficiency of biomass and energy transfer between trophic levels

Answer 5

• Biomass in trophic level less than trophic level below
• Only a small proportion of food that an animal ingests is turned into new tissue, and only this is transferred to the next trophic level
• Biomass = energy
• Energy available at each trophic level = kilojoules per metres squared per year which allows changes in photosynthesis production and feeding patterns

Question 6

What is the efficiency like at producer level?

Answer 6

• Only convert 1-3% of sunlight into biomass
• Not all solar energy used for photosynthesis
• Other factors limit photosynthesis
• Some energy is lost as it is used in photosynthetic reactions

Question 7

What is gross production?

Answer 7

• total solar energy plants convert to organic matter
• plants use 20-50% of energy in respiration, the rest is biomass
• the rest of net production

Question 8

What is the equation for net production ?

Answer 8

Net production = gross production - respiratory losses

Question 9

How is the efficiency at consumer levels?

Answer 9

• consumers convert 10% of biomass in their food
• not all biomass is eaten e.g bones
• energy transferred e.g metabolic heat
• some parts are indigestible and egested like faeces
• some energy is lost through excretory materials like urine

Question 10

How to work out ecological efficiency?

Answer 10

(Energy or biomass available after the transfer/ energy or biomass available before transfer) x 100

Question 11

How do humans manipulate biomass in ecosystems?

Answer 11

Agriculture:

• growing specific crops or rearing specific animals
• env is adapted to suit certain species
• competition is removed
• good because only 2 trophic levels so energy is transferred more efficiently