Fish farming and non-indigenous species (Edexcel), the carbon cycle in numbers, the water cycle in depth, and what speeds up or slows down decomposition (Biology only).
What you will learn
- Describe the benefits and problems of fish farming and work out feed and fishmeal figures (Edexcel)
- Explain how non-indigenous species reduce biodiversity and analyse population data (Edexcel)
- Use carbon cycle figures to find the overall change in the atmosphere
- Explain run-off, transpiration and desalination in the water cycle
- Explain how temperature, water, oxygen and surface area change the rate of decomposition, and calculate it (Biology only)
Fish farming (Edexcel)
Fish farms keep large numbers of fish in cages or tanks and feed them a high-protein diet; limiting their movement and keeping the water at a good temperature means less energy is used in respiration, so they grow fast.
Farming gives a lot of protein-rich food and can take pressure off wild stocks.
But it has costs for biodiversity: diseases and parasites such as sea lice spread among the crowded fish and pass to wild fish; uneaten food and faeces cause eutrophication; escaped fish compete and breed with wild fish; and fishmeal for the feed is often made from wild fish.
- 2400 kg of feed; the salmon gained 1600 kg
- 1600 ÷ 2400 × 100 = 66.67% of the feed became fish
- 25% of the feed is fishmeal: 25 ÷ 100 × 2400 = 600 kg
- each kg of fishmeal needs 3 kg of wild fish: 600 × 3 = 1800 kg
The rest of this lesson and its 12 practice questions are locked.
In this lesson
- Fish farming (Edexcel)
- Non-indigenous species (Edexcel)
- The carbon and water cycles in depth
- The rate of decomposition (Biology only)
- Try it: In and out
12 practice questions, marked as you go; about 25 minutes in all.
Key terms
Non-indigenous, Evaporation, Transpiration, Condenses, Precipitation, Run-off, Desalination, Warm but not hot, Moist, Oxygen
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