Condensed notes on the topics in the Biology GCSE (AQA spec but also relevant to many other courses) that I found the hardest to remember and understand. Topics include:
- Human Influences on the Environment (including effects of farming and pollution)
- Gas Exchange and Transport in Plants
Ec...
Biology
Human Influences on the Environment
Eutrophication
• Fertilisers or sewage are leached into water
• Nitrate levels rise
• Causes algae to grow – algal bloom
• Light is blocked so plants can’t photosynthesize
• Plants die and are decayed by bacteria
• Water becomes anoxic – more respiration from bacteria
• Aerobic fish die
Pesticides
Chemical Pesticides – chemical poisons that kill pests (e.g. DDT)
• Easy to use
• Fast effect
• Cheap
• Reduces biodiversity
• Pesticide resistance
• Bioaccumulation
Biological control – using a predator to control pest numbers (e.g. cane toad)
• Single use
• Specific to pest
• No bioaccumulation or toxins
• Difficult to contain and control
• Doesn’t completely eliminate pest
• Imbalance to food chain and ecosystem
Acid Rain
Sulfuric Acid – sulphur dioxide released from fossil fuels, dissolves in rain
Nitric Acid – nitrogen oxides released in car fumes, dissolve in rain
Effects:
• Damages leaves and roots- can’t photosynthesize or get minerals
• Acidic lakes – fish die/don’t hatch, amphibians’ skin is damaged
• Ions dissolve more, so are leached away with rain, reducing soil fertility
, Carbon Monoxide
Made during incomplete combustion of fossil fuels and plastics
Bonds strongly to haemoglobin in blood, reducing its ability to carry oxygen
Global Warming
Greenhouse Gases:
• Carbon dioxide – from fossil fuels
• Methane – from agriculture, e.g. cows, rice
• CFCs – from aerosols and refrigerators
Greenhouse gases – short-wave radiation from sun is absorbed and reflected by
greenhouse gases as long-wave radiation – stuck in atmosphere
Effects:
• Rising sea levels
• Changes in ocean currents
• Changes in rainfall patterns
• Changes in migration patterns
• New crop pests
• Species extinction
Deforestation
Causes:
• Agriculture
• Population increase – housing
• Wood used for timber
Effects:
• Erosion of soil
• Ions leached
• Imbalance of water cycle
• Carbon dioxide levels rise
• Oxygen levels decrease
• Loss of habitats
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