Transfer of Biomass | Biology

📖 In-Depth Theory

Why Biomass Is Lost at Each Level

When an organism is eaten, not ALL of its biomass is transferred to the predator.

BIOMASS IS LOST BECAUSE:

1. RESPIRATION:

Organisms use energy from food for movement, growth, reproduction, and maintaining body temperature.

This energy is released as HEAT to the surroundings — not available to the next level.

Warm-blooded (endothermic) animals lose proportionally more energy keeping warm.

2. EGESTION:

Not all food consumed is digested — indigestible material (cellulose in plant cell walls, bones) is excreted as FAECES.

Faeces energy is lost to decomposers, not to the next trophic level.

3. EXCRETION:

Waste products of metabolism (urine, urea) are excreted — energy in these molecules is lost.

4. MOVEMENT:

Energy used for movement is released as heat.

ONLY the energy that becomes part of the organism's OWN BIOMASS (growth) is available to the next level.

Efficiency of Energy Transfer

The EFFICIENCY of energy transfer between trophic levels is typically about 10%.

EFFICIENCY EQUATION:

Efficiency (%) = (biomass transferred to next level ÷ biomass at current level) × 100

EXAMPLE:

Grass has biomass of 1000 g/m².

Grasshoppers consuming this grass have biomass of 100 g/m².

Efficiency = (100 ÷ 1000) × 100 = 10%

APPLICATION — Why eating lower in the food chain is more efficient:

If humans eat grain (trophic level 2): 10% of grain energy available to us.

If humans eat beef (trophic level 3): only 10% × 10% = 1% of original grain energy available.

Eating lower in the food chain is 10× more energy-efficient — important for global food security.

FARMING IMPLICATIONS:

Reducing energy losses from farm animals INCREASES efficiency:

Keeping animals warm → less energy wasted maintaining body temperature.

Limiting movement → less energy wasted on movement.

Result: more biomass available for human consumption.

Calculating Biomass Transfers

WORKED EXAMPLE:

A pond has 10,000 g/m² of algae (level 1).

Small fish eat algae and have biomass of 1000 g/m² (level 2).

Large fish eat small fish and have biomass of 100 g/m² (level 3).

Efficiency level 1→2: (1000 ÷ 10,000) × 100 = 10%

Efficiency level 2→3: (100 ÷ 1000) × 100 = 10%

WHAT HAPPENED TO THE OTHER 90% AT EACH LEVEL?

About 60–70%: used in respiration → heat.

About 20–30%: lost in egestion (undigested food).

Small fraction: lost in excretion.

INTERPRETING DATA:

If given biomass at two consecutive levels, can calculate:

Mass transferred = biomass at next level.

Mass not transferred = biomass at current level − biomass at next level.

% efficiency = (next level biomass ÷ current level biomass) × 100.

⚠️ Common Mistake

The 10% transferred is the biomass that becomes part of the predator's BODY — not the amount eaten. An animal may eat 1000 g of prey but only incorporate 100 g into its own biomass (10%). The rest is lost through respiration, egestion and excretion.

📐 Key Equations

Efficiency (%) = (biomass transferred ÷ biomass at current level) × 100

📌 Key Note

Biomass lost at each level due to: respiration (heat), egestion (faeces), excretion. ~10% efficiency per transfer. Efficiency = (next level ÷ current level) × 100. Eating lower in food chain more efficient. Restricting farm animal movement and controlling temperature improves efficiency.

🎯 Matching Activity — Biomass Transfer

Match each reason for biomass loss to the correct description. — drag the symbols on the right to match the component names on the left.

Respiration

Drop here

Egestion

Drop here

Excretion

Drop here

~10% efficiency

Drop here

Waste metabolic products (urine) removed — energy in these compounds is lost

Energy used for life processes released as heat — not passed to next trophic level

Only about 1/10 of biomass at each level is transferred to the next

Indigestible material leaves as faeces — energy goes to decomposers not predators

⚽ FIFA Worked Examples

Efficiency Calculation

Grass has biomass 2000 g/m². Rabbits eating this grass have biomass 160 g/m². Calculate the efficiency of transfer.

F

Efficiency (%) = (biomass at next level ÷ biomass at current level) × 100

I

Next level (rabbits) = 160; Current level (grass) = 2000

F

Efficiency = (160 ÷ 2000) × 100 = 0.08 × 100

A

Efficiency = 8%

🔬 Triple Science Only

Transfer of biomass (4.7.4.3) is biology-only. Includes calculating efficiency of biomass transfer, reasons for biomass loss (respiration, egestion, excretion), and the implications for farming and food security.

🎯 Test Yourself

Question 1 of 2

1. Producers have biomass 5000 g/m². Primary consumers have biomass 500 g/m². What is the efficiency of transfer?

2. Why do intensive farming methods restrict farm animals' movement to improve food production efficiency?

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🌿 Transfer of Biomass

Why Biomass Is Lost at Each Level

Efficiency of Energy Transfer

Calculating Biomass Transfers

Mr. Badmus AI