Edexcel (Biology only): controlling pests with living organisms and weighing it against pesticides; and how persistent pesticides build up along food chains, with the calculations data questions ask for.
What you will learn
- Explain what biological control is and evaluate it against chemical pesticides (Edexcel, Biology only)
- Name the control agent and the pest in an example, and say what could go wrong
- Explain why a persistent pesticide is most concentrated in top predators
- Calculate concentration factors and the pesticide a predator takes in
Biological control (Edexcel, Biology only)
Biological control uses a living organism, such as a predator, parasite or pathogen, to reduce the numbers of a pest.
Ladybirds eat aphids; tiny wasps lay their eggs inside whitefly larvae in greenhouses, where the wasps cannot escape and the warmth suits them; nematode worms infect slugs.
| Biological control | Chemical pesticide | |
|---|---|---|
| speed | slow to take effect | fast |
| other species | usually targets one pest, but may harm others | often kills useful species too |
| residues | none | can remain on food and build up in food chains |
| repeat use | the agent breeds, so it keeps working | must be sprayed again; pests can become resistant |
Biological control rarely wipes the pest out: when the pest is rare, the control organism has less food, so its numbers fall too. And it can go badly wrong. Cane toads were brought to Australia to eat beetles in sugar cane; they ate many other animals, spread widely and poisoned native predators that ate them.
Edexcel also asks you to compare biological control with fertilisers, which add mineral ions such as nitrates so crops grow faster; they do not control pests.
In an example, the control agent is the organism doing the controlling; the pest is what it eats or infects.
The rest of this lesson and its 10 practice questions are locked.
In this lesson
- Biological control (Edexcel, Biology only)
- Bioaccumulation
- Try it: Who controls whom?
10 practice questions, marked as you go; about 25 minutes in all.
Key terms
Biological control, Fertilisers, Bioaccumulation
In this unit: Ecology
Communities and adaptations, sampling with quadrats, transects and capture-recapture, food chains and the carbon, water and nitrogen cycles, decay, parasitism and mutualism, eutrophication, biodiversity and human impact, biomass transfer and food security.
- Communities, interdependence and adaptations
- Sampling with quadrats, transects and capture-recapture
- Food chains, cycles and decay
- Biodiversity and human impact
- Trophic levels, pyramids and efficiency
- Food security and farming
- Biological control and bioaccumulation
- Fish farming, introduced species and the cycles in depth