Environment, Ecology and Conservation
This domain tests how organisms depend on each other and their surroundings, how energy moves through food chains, and how human activity can help or harm ecosystems.
Key ecological terms
A population is all members of one species in an area; a community is all the populations living there; a habitat is where an organism lives; an ecosystem is the community plus the physical environment. Producers make their own food by photosynthesis, consumers eat other organisms, and decomposers break down dead material and return nutrients to the soil.
Food chains, energy and adaptation
A food chain starts with a producer. Arrows point from the organism being eaten to the eater, showing the direction of energy transfer. Energy is lost as heat at each level, so fewer organisms can be supported further along the chain. Organisms have adaptations - sharp beaks, camouflage, waxy leaves, stored water - that help them survive, and they compete for light, water, food and space.
Human impact and conservation
Deforestation destroys habitats and can cause soil erosion. Fertilisers washed into rivers cause eutrophication, where algae bloom and later decay, removing oxygen from the water. Plastic waste harms wildlife, and overfishing reduces populations. Conservation includes protected areas, replanting trees, recycling, reducing waste and biological pest control.
Worked example
Removing a predator from a food chain lets its prey population rise. The prey then overgrazes the producers, and animals further along the chain lose food, so the whole community is affected.
Traps that cost marks
Do not put the Sun as a link in the food chain; it is the energy source, not an organism. Never reverse the arrows. Decomposers are not the same as predators, and a pyramid of numbers is not the same as a pyramid of energy.