Toxic build-up along a food chain
A pollutant too dilute to harm a single organism can still kill a top predator, because food chains concentrate what they cannot excrete.
Part of your national curriculum
- Biology: interactions and interdependencies: Understand how organisms affect, and are affected by, their environment, including the accumulation of toxic materials
Lesson overview
What you'll learn in this lesson
Understand how organisms affect, and are affected by, their environment, including the accumulation of toxic materials
Key learning points
- • Why concentration climbs
- • Evidence in the field
- • Other ways organisms change environments
This lesson at a glance
- 25 minutes
- 20 parts to scroll through
- 4 quick checks
- Marked quiz at the end
- Gentle pace: short sittings with pauses
Words to know
Scroll down — the lesson carries on below
Watch & discover
Part 1 of 20
Visual introductionPicture this
Toxic build-up along a food chain
A pollutant too dilute to harm a single organism can still kill a top predator, because food chains concentrate what they cannot excrete.
In a nutshell
Understand how organisms affect, and are affected by, their environment, including the accumulation of toxic materials
Learning cycle
Part 2 of 20
Learning cycle 1 of 2
Part 1 · Why concentration climbs
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 3 of 20
Learn
Why concentration climbs
Some substances, such as certain pesticides and mercury compounds, are not broken down or excreted. Each consumer eats many organisms from the level below, so the toxin from all of them accumulates in one body. At each step the concentration in tissue rises.
Reset break
Part 4 of 20
Pause
That's sitting 1 of 5 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Explore the idea
Part 5 of 20
Learn
Evidence in the field
Populations of birds of prey fell sharply in the mid-twentieth century where persistent pesticides were used; thinning eggshells meant fewer chicks hatched. When the pesticides were restricted, populations slowly recovered — evidence linking cause and effect over time.
Quick check
Part 6 of 20
Quick check
Part 7 of 20
Reset break
Part 8 of 20
Pause
That's sitting 2 of 5 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Learning cycle
Part 9 of 20
Learning cycle 2 of 2
Part 2 · Other ways organisms change environments
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 10 of 20
Learn
Other ways organisms change environments
Accumulation is one route. Organisms also change their environment by competing, spreading disease, altering soil and, in the case of humans, changing land use, water flow and atmosphere composition.
Quick check
Part 11 of 20
Reset break
Part 12 of 20
Pause
That's sitting 3 of 5 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Quick check
Part 13 of 20
Explore the idea
Part 14 of 20
Worked example
Worked example: reading concentration data
Water 0.001 ppm, plankton 0.05 ppm, small fish 1 ppm, heron 20 ppm. Conclusion: concentration rises at each trophic level, so the toxin is persistent and stored in tissue. The heron is most at risk despite never touching a lethal dose in any single meal.
Challenge round
Part 15 of 20
Game · Sort it
Which of these are true?
Drag each card into the right column. Tap a card first if dragging is fiddly.
True
Not true
Reset break
Part 16 of 20
Pause
That's sitting 4 of 5 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Challenge round
Part 17 of 20
Game · Fill the gaps
Finish the sentences
Choose the word that belongs in each gap.
Each consumer eats many ____ from the level below, so the toxin from all of them accumulates in one body.
____ is one route.
Organisms also change their ____ by competing, spreading disease, altering soil and, in the case of humans, changing land use, water flow and atmosphere composition.
Challenge round
Part 18 of 20
Game · Recall cards
An arrow in a food chain points…
Card 1 of 4
Mastery quiz
Part 19 of 20
Marked quiz
End of lesson quiz: Toxic build-up along a food chain
4 questions, marked with the reasoning shown. No timer.
1. An arrow in a food chain points…
2. Roughly how much energy passes to the next trophic level?
3. Removing a top predator most likely…
4. Predator numbers usually peak…
Lesson round-up
Part 20 of 20
Lesson round-up
Ready when you are
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Ask LunaPart 1 of 20 · Watch & discover
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Understand how organisms affect, and are affected by, their environment, including the accumulation of toxic materials