Oxford, Cambridge and RSA Examinations (OCR) is an examination board that sets examinations and awards qualifications (including GCSEs and A-levels). It is one of England,Wales and Northern Ireland's five main examination boards.

A female hormone that causes development and change in the reproductive organs

Oral contraceptives are medicines taken by mouth to help prevent pregnancy. They are also known as the Pill, OCs, or birth control pills

Expansion or development of land to the point of damage

Fishing with a sufficiently high intensity to reduce the breeding stock levels to such an extent that they will no longer suppport a sufficient quantity of fish for sport or commercial harvest

A naturally occurring, highly reactive gas comprising triatomic oxygen formed by recombination of oxygen in the presence of ultraviolet radiation. 

The reduction of the protective layer of ozone in the upper atmosphere by chemical pollution.

A hole or gap in the protective layer of ozone in the upper atmosphere.