How living things change their environment - and how poisons build up
Organisms are not just passengers in their habitat; they change it, and it changes them back. This lesson finishes with bioaccumulation, the reason a tiny trace of a toxin can kill a top predator.
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
- • Organisms shape their habitat
- • The habitat pushes back
- • Bioaccumulation
- • Biomagnification up a chain
This lesson at a glance
- 30 minutes
- 19 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 19
Watch first
How living things change their environment - and how poisons build up
An English teaching video on this topic from MightyOwl. Watch it, then scroll down for the lesson.
Do it for real
The practicals below use what the film shows, with a full method you can follow at home.
In a nutshell
Understand how organisms affect, and are affected by, their environment, including the accumulation of toxic materials
What you already know
Part 2 of 19
Before we start
What you already know
You should know what a food chain is and that organisms depend on their habitat for food and shelter.
Key words
Part 3 of 19
Key words
Words you'll need today
- Habitat
- The place where an organism lives.
- Biotic factor
- A living influence on an organism, such as a predator or competitor.
- Abiotic factor
- A non-living influence, such as temperature, light or water.
- Bioaccumulation
- The build-up of a substance in an organism's body over time.
- Biomagnification
- The rising concentration of a toxin at each step up a food chain.
Learning cycle
Part 4 of 19
Learning cycle 1 of 2
Two-way effects between organisms and habitat
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 5 of 19
Learn
Organisms shape their habitat
A beaver dams a stream and creates a pond; earthworms drag leaves down and turn compacted soil into something that drains and holds air; trees shade the ground, drop leaf litter and slow the wind. Every one of these changes the conditions for other species. Some organisms create habitat for others - one oak can support hundreds of species.
Explore the idea
Part 6 of 19
Learn
The habitat pushes back
Abiotic factors - light, temperature, water, oxygen, pH - set what can survive where. Biotic factors like predators, competitors and disease set the rest. Change a factor and numbers shift: warm a river by a few degrees and it holds less dissolved oxygen, so the fish that need most oxygen go first, and everything that eats them follows.
Quick check
Part 7 of 19
Quick check
Which is an abiotic factor?
Quick check
Part 8 of 19
Quick check
Earthworms affect their environment mainly by...
Reset break
Part 9 of 19
Pause
That's sitting 1 of 2 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 10 of 19
Learning cycle 2 of 2
Toxins that build up
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 11 of 19
Learn
Bioaccumulation
Some substances - certain pesticides, mercury, some plastics-borne chemicals - are not broken down and not excreted. They stay in the body, so the amount rises through an organism's life. A single day's exposure looks harmless; a decade of it does not. That difference between dose per day and total load is the whole idea.
Explore the idea
Part 12 of 19
Learn
Biomagnification up a chain
A predator eats many prey animals, and takes on the toxin from all of them. So concentration multiplies at each step: barely detectable in water, higher in algae, higher again in small fish, and dangerous in a top predator like an otter or an osprey. That is why the pesticide DDT thinned bird of prey eggshells across Britain while the sprayed insects seemed unaffected.
Quick check
Part 13 of 19
Quick check
Bioaccumulation means a substance...
Quick check
Part 14 of 19
Quick check
Why is a top predator most at risk from a persistent pesticide?
Common mix-ups
Part 15 of 19
Common mix-ups
Things people often get wrong
- Toxins become more concentrated up a chain, not less.
- Abiotic means non-living; biotic means living.
- 'Low concentration in the water' does not mean safe for top predators.
- Organisms change their habitat as well as being changed by it.
Challenge round
Part 16 of 19
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
Challenge round
Part 17 of 19
Game · Fill the gaps
Finish the sentences
Choose the word that belongs in each gap.
Some ____ create habitat for others - one oak can support hundreds of species.
Mastery quiz
Part 18 of 19
Marked quiz
End of lesson quiz: How living things change their environment - and how poisons build up
6 questions, marked with the reasoning shown. No timer.
1. Warming a river reduces...
2. Biomagnification describes concentration rising...
3. Which factor is biotic?
4. DDT harmed birds of prey mainly by...
5. A substance is most likely to bioaccumulate if it is...
6. One oak tree supporting hundreds of species is an example of an organism...
Lesson round-up
Part 19 of 19
Lesson round-up
Ready when you are
Quiz score
Not sat
Games
Not played
Points this lesson
0
Best run
0 in a row
Luna: 0 out of 4 on the practice checks. Only if you feel up to it — one more?
Ask LunaDo the work
Your written work for this lesson
This is the part you'd do in your book at school. Pick the pieces below, write here or on paper, and photograph anything you draw or work out.
Why the school greenhouse failed
A science club grew tomato plants in the school greenhouse. In June the plants grew well: leaves were dark green and the fruit set quickly. In July the club went away for two weeks and left the greenhouse door shut. When they came back, the leaves were curled and pale and most of the fruit had dropped.
The club had a data logger inside. It showed the temperature reached 46 °C on several afternoons and the soil moisture fell close to zero. The club knew photosynthesis needs light, water and carbon dioxide, and that enzymes in a plant work best in a narrow range of temperature. Above that range the enzymes stop working properly.
The club repeated the summer with the door propped open and a water bottle drip on each pot. Temperature peaked at 31 °C and the plants survived.
Written for Good Learning Co.
Reading questions
- Name the variable the club changed the second time, and one variable they kept the same.
- Explain, using the words photosynthesis and enzymes, why the plants were damaged in July.
- Write a conclusion for the club's report, saying how far the evidence supports it.
Method and results
WritingWrite the aim, what you changed, what you measured and what you kept the same, then record your results in a table.
1 page + results table
Conclusion
WritingExplain what your results show and why, using the scientific words from the lesson. Say how you know you can trust them.
6–8 sentences
Labelled diagram
DiagramDraw the apparatus or the process in pencil, label it fully, and photograph it.
1 labelled diagram
Reading and notes
ReadingRead the lesson text again and write the key ideas in your own words.
Half a page of notes
Saved as you type.
Part 1 of 19 · Watch & discover
How this is going
- Not looked at yet
Understand how organisms affect, and are affected by, their environment, including the accumulation of toxic materials