GCSE Biology - Pyramids of Biomass #87

Summary

This video explains biomass pyramids, illustrating the decreasing mass of organisms across trophic levels in a food chain. It uses an example with grass, rabbits, snakes, and hawks, highlighting how only about 10% of biomass and energy is transferred to the next level due to consumption inefficiencies, indigestibility, and energy use for respiration. The video concludes with a formula to calculate biomass transfer efficiency as a percentage.

Takeaways

• 🌿 Biomass pyramids represent the mass of living organisms at each trophic level in a food chain.
• 🐰 Grass is the producer, rabbits are primary consumers, snakes are secondary consumers, and hawks are tertiary consumers.
• 📊 The bars in the pyramid decrease in size as you move up the trophic levels, indicating a reduction in total mass of organisms.
• 🐍 Even though a snake is heavier than a rabbit, there are fewer snakes, leading to less total biomass.
• 🔄 Approximately 10% of biomass and energy is transferred to the next trophic level with each consumption.
• 🦅 Organisms don't consume every part of what they eat, leading to biomass loss.
• 💩 Consumed parts that aren't absorbed are excreted as waste, reducing the biomass passed on.
• 🔥 Most absorbed nutrients are used for energy release through respiration, not stored indefinitely.
• 📉 Biomass is often released as waste products like CO2 and urea, not retained by the organism.
• 📊 To calculate biomass transfer efficiency, use the formula: (biomass transferred / biomass available) * 100.

Q & A

What does a pyramid of biomass represent?

A pyramid of biomass represents the total mass of living organisms at each trophic level in a food chain.

What is the significance of the bars in the biomass pyramid?

The bars in the biomass pyramid get smaller as you go up the trophic levels, indicating that the total mass of organisms decreases with each level.

Why do the bars get smaller as you move up the trophic levels?

The bars get smaller because only about 10% of the biomass and energy is transferred to the next trophic level when one organism is consumed by another.

What are the three main reasons that only about 10% of the biomass and energy gets passed on each time?

The three main reasons are: 1) Organisms don't eat every part of their prey, 2) Some parts consumed are not absorbed and are excreted, and 3) Most nutrients absorbed are used for respiration and are released as waste products.

Why might a hawk not eat the entire snake it catches?

A hawk might not eat the entire snake because it doesn't consume parts like the skeleton or teeth, which are not digestible.

What is meant by biomass being 'used for respiration'?

Biomass being 'used for respiration' means that the nutrients are used to release energy, which is then released as waste products like carbon dioxide and urea, rather than being stored within the organism.

How is the efficiency of biomass transfer calculated?

The efficiency of biomass transfer is calculated as the percentage of biomass that has passed on to the next trophic level, using the formula: (biomass transferred to the next level / biomass available at the previous level) * 100.

What is the efficiency of biomass transfer between rabbits and snakes in the given example?

The efficiency of biomass transfer between rabbits and snakes is 10.4 percent, calculated as (15 kg / 144 kg) * 100.

What is the efficiency of biomass transfer between snakes and hawks in the given example?

The efficiency of biomass transfer between snakes and hawks is 10.7 percent, calculated as (1.6 kg / 15 kg) * 100.

Why is it important to understand the efficiency of biomass transfer?

Understanding the efficiency of biomass transfer is important because it helps us understand how energy and nutrients flow through an ecosystem and how much is lost at each trophic level.