Inaugurated by IN-SPACe
ISRO Registered Space Tutor
S4-SA3-0853
What is the 10 Percent Law (biology)?
Grade Level:
Class 6
Space Technology, EVs, Climate Change, Biotechnology, HealthTech, Robotics, Chemistry, Physics
Definition
What is it?
The 10 Percent Law in biology states that only about 10% of the energy from one trophic level is transferred to the next trophic level. The remaining 90% of the energy is lost as heat or used for life processes like breathing and moving.
Simple Example
Quick Example
Imagine you have 100 rupees. If you give 10% of that money to your friend, they get 10 rupees. In the same way, if a plant has 100 units of energy, the animal that eats it only gets about 10 units of that energy.
Worked Example
Step-by-Step
Let's say a field of grass (producers) has 10,000 units of energy.
---
Step 1: Calculate the energy transferred to primary consumers (like a deer eating the grass). Only 10% is transferred. So, 10% of 10,000 units = (10/100) * 10,000 = 1,000 units.
---
Step 2: Now, calculate the energy transferred to secondary consumers (like a tiger eating the deer). Only 10% of the deer's energy is transferred to the tiger. So, 10% of 1,000 units = (10/100) * 1,000 = 100 units.
---
Step 3: If a tertiary consumer (like a larger predator) eats the tiger, it would get 10% of 100 units = 10 units.
---
Answer: A tiger would get 100 units of energy from eating the deer, which ate the grass with 10,000 units of energy.
Why It Matters
Understanding the 10 Percent Law helps us see why food chains are usually short and why there are fewer top predators. This concept is crucial for environmental scientists studying climate change impacts on ecosystems and for biotechnologists developing sustainable food systems. It even helps us understand how much land is needed to feed a population.
Common Mistakes
MISTAKE: Thinking 90% of energy is transferred. | CORRECTION: Only 10% of energy is transferred to the next level; 90% is lost or used up.
MISTAKE: Believing the 10% rule applies to biomass (weight) directly. | CORRECTION: The 10% rule specifically refers to the transfer of energy, not necessarily the exact weight or number of organisms.
MISTAKE: Assuming the energy loss is only due to predation. | CORRECTION: Energy is lost at each level mainly as heat during metabolic processes (like breathing, digestion) and through waste products, not just when one animal eats another.
Practice Questions
Try It Yourself
QUESTION: If producers have 5,000 units of energy, how much energy will primary consumers get? | ANSWER: 500 units
QUESTION: A hawk (tertiary consumer) gets 20 units of energy from eating a snake (secondary consumer). How much energy did the plant (producer) originally have? | ANSWER: 2000 units (Plant -> Primary Consumer: 200 units, Primary Consumer -> Snake: 20 units, Snake -> Hawk: 2 units. Wait, calculation error in the question setup. Let's re-correct for the answer to be 2000 units for a Class 6 student. If Hawk gets 20 units, Snake had 200 units (20/0.1), Primary Consumer had 2000 units (200/0.1), Plant had 20,000 units (2000/0.1). Let's make the question simpler: A hawk (secondary consumer) gets 20 units of energy from eating a mouse (primary consumer). How much energy did the plant (producer) originally have? ANSWER: 2000 units (Plant -> Mouse: 200 units, Mouse -> Hawk: 20 units).
QUESTION: A food chain consists of grass -> rabbit -> fox. If the grass has 8,000 units of energy, how much energy will the fox receive? What happens to the remaining energy at each step? | ANSWER: The rabbit will receive 800 units (10% of 8,000). The fox will receive 80 units (10% of 800). The remaining 90% at each step is lost as heat or used for the organism's life processes.
MCQ
Quick Quiz
What percentage of energy is typically transferred from one trophic level to the next?
0.01
0.1
0.5
0.9
The Correct Answer Is:
B
According to the 10 Percent Law, only about 10% of the energy is transferred to the next trophic level. The rest is lost as heat or used by the organism.
Real World Connection
In the Real World
This law helps explain why vegetarian diets are often considered more energy-efficient. For example, if we eat plants directly (like dal, roti, sabzi), we get energy closer to the source. If we eat meat from an animal that ate plants, we are getting energy from a higher trophic level, meaning much more original plant energy was needed to produce that meat.
Key Vocabulary
Key Terms
TROPHIC LEVEL: The position an organism occupies in a food chain | PRODUCERS: Organisms that make their own food, like plants | CONSUMERS: Organisms that get energy by eating other organisms | ENERGY TRANSFER: The movement of energy from one living thing to another | FOOD CHAIN: A sequence showing how energy is transferred from one living thing to another
What's Next
What to Learn Next
Now that you understand energy transfer in food chains, you can explore Food Webs, which are more complex networks of interconnected food chains. You can also learn about ecological pyramids, which visually represent how energy, biomass, and numbers decrease at higher trophic levels.
