CSEC Biology notes on human impact, natural resources, deforestation, pollution, climate change, recycling, conservation, and ecological investigations.
This page covers the part of Section A where ecology meets real life: how human activity affects ecosystems and how careful management can reduce damage.
Natural resources are materials or energy sources obtained from the environment.
Renewable resources can be reused or replenished quickly if managed properly. Examples include solar, wind, tidal, and geothermal energy.
Non-renewable resources exist in limited amounts and cannot be replaced quickly. Examples include coal, oil, natural gas, and minerals such as bauxite. Fossil fuels take millions of years to form, so they are effectively lost once used.
Bauxite is the ore from which aluminium is obtained. Mining bauxite can support industry and exports, but it can also damage habitats, remove vegetation, and disturb soil if not managed carefully.
Human activities can change ecosystems faster than many organisms can adapt.
Major human impacts include:
Deforestation is the removal of forests.
Effects include:
Greenhouse gases trap heat near the Earth's surface. Carbon dioxide and water vapour are examples of greenhouse gases.
Human activities such as burning fossil fuels and deforestation increase carbon dioxide levels.
Possible effects include higher global temperatures, melting ice caps, rising sea levels, ocean acidification, flooding of low-lying areas, changes in rainfall patterns, and stress on crops and ecosystems. Small island states are especially vulnerable because many communities, roads, hotels, beaches, wetlands, and coral reefs are close to sea level.
A clear climate-change answer follows the chain: more greenhouse gases → more heat trapped → global warming → environmental effects.
An invasive species is a species introduced into an area where it is not native and where it causes harm.
Invasive species may outcompete native species, have few natural predators, spread disease, damage crops, alter food webs, and reduce biodiversity.
Pollution is the addition of harmful substances to the environment. These harmful substances are called pollutants.
| Pollutant | Common Source | Effects |
|---|---|---|
| Sulphur dioxide | burning fossil fuels, industry | irritates lungs, forms acid rain |
| Nitrogen oxides | vehicle exhausts, industry | respiratory problems, acid rain |
| Carbon monoxide | motor vehicle exhaust | combines with haemoglobin and reduces oxygen transport |
| Carbon dioxide | combustion, deforestation | contributes to global warming |
Sulphur dioxide and nitrogen oxides can react with rainwater to form acids.
Effects of acid rain:
Water and land pollution can come from:
Effects include:
Agricultural pollution may come from chemical fertilisers and pesticides. Fertilisers can be washed into rivers and seas, where they may encourage excessive algal growth and reduce oxygen availability for aquatic organisms.
Pollution answers are clearest when they connect source → pollutant → effect. For example: vehicle exhaust releases carbon monoxide, which combines with haemoglobin and reduces oxygen transport in the blood.
Marine and wetland ecosystems are especially important in the Caribbean. They support fisheries, tourism, coastal protection, biodiversity, and recreation.
Pollution of marine and wetland environments can:
Polluted runoff entering a coral reef can reduce water quality, encourage algal growth, and make the reef less attractive for tourism while also damaging the habitat of many marine organisms.
Waste may be biodegradable or non-biodegradable.
Biodegradable waste can be broken down by microorganisms.
Non-biodegradable waste cannot be broken down easily and may remain in the environment for a long time.
The 3Rs are:
| Strategy | Meaning | Example |
|---|---|---|
| Reduce | use less material in the first place | avoid disposable cutlery |
| Reuse | use an item again instead of throwing it away | reuse a bottle as a container |
| Recycle | process waste material to make new products | recycling paper, glass, or plastic |
Recycling conserves land, reduces pollution, saves energy, saves raw materials, and reduces the amount of waste sent to landfills.
Recycling may be difficult because people must sort garbage correctly, collection systems must be organised, and recycling may cost more than using raw materials.
Conservation is the careful management and protection of natural resources and ecosystems.
Conservation methods include:
Conservation means using resources carefully so they remain available. Preservation means protecting an area or species from use or disturbance as much as possible.
Sustainable use means using resources at a rate that allows them to be replaced naturally or managed for future use.
Examples:
Human impact questions may use graphs, tables, maps, or field investigations.
You may be asked to:
Aim: To compare the number of plant species in a shaded area and an open area.
Possible method:
| Variable Type | Example |
|---|---|
| Independent variable | habitat type: shaded or open |
| Dependent variable | number of plant species |
| Controlled variables | quadrat size, number of samples, sampling method |
Useful precautions:
The best sampling method depends on the habitat and organism.
| Method or Equipment | Best Used For |
|---|---|
| Quadrat | estimating plant or slow-moving organism distribution in a measured area |
| Line transect | studying how organisms change along a line across a habitat |
| Belt transect | sampling a strip of habitat, useful where conditions change across an area |
| Pooter | collecting small insects safely |
| Net | collecting flying insects or aquatic organisms |
| Sieve | separating small organisms from soil or leaf litter |
| Bottle or jar | temporary collection and observation |
| Mark, release, recapture | estimating population size of mobile animals |
Density can be estimated as:
For ecological sampling, the method should match the organism. A quadrat suits plants better than flying insects; a net suits flying or aquatic organisms better than rooted plants.
Human activity can damage ecosystems, but conservation, sustainable use, pollution control, and better waste management can reduce the impact.