Sustainability and Interdependence: overview of SQA Higher Biology Area 3

Sustainability and Interdependence is the third of the three areas of SQA Higher Biology. It explores the biology behind feeding a growing population sustainably, the relationships between species, and the threats facing the variety of life. This page maps the six key areas and shows how they connect.

The six key areas

Food supply and photosynthesis

Sustainable food production for a growing population depends on photosynthesis, where the light reactions and carbon fixation make sugars, limited by light, carbon dioxide and temperature.

Plant and animal breeding

Inbreeding, crossbreeding (F1 hybrids and hybrid vigour) and genetic technology improve yield and resistance, and new varieties are tested in randomised, replicated field trials.

Crop protection

Weeds, pests and disease reduce yield; control uses selective and systemic pesticides, cultural and biological control, and integrated pest management.

Animal welfare

Intensive and free-range systems trade productivity against welfare, which is judged from behavioural indicators such as stereotypy and misdirected behaviour.

Symbiosis and social behaviour

Parasitism and mutualism are co-evolved relationships, while social hierarchy, co-operative hunting, social defence, altruism and kin selection aid survival in groups.

Biodiversity and mass extinction

Biodiversity has genetic, species and ecosystem components; human activity threatens it, raising the prospect of a sixth mass extinction.

How to study Area 3

1. Master the photosynthesis stages. Know what the light reactions and carbon fixation produce and use.
2. Compare and evaluate. Breeding methods, control methods and farming systems are often tested as costs and benefits.
3. Define the behaviour terms. Mutualism, parasitism, altruism and kin selection need precise definitions.
4. Link to sustainability. Tie each key area back to feeding people without degrading the environment.

For the official course specification

The SQA publishes the full Higher Biology course specification, specimen and past papers, and marking instructions at sqa.org.uk. Always revise from the current specification and SQA past papers.