OCR GCSE Combined Science A key terms

A viral pathogen that causes mosaic-like leaf discolouration and reduced growth in tobacco and other plants.

The extent to which a substance causes harmful effects.

A compromise in which improving one aspect of a choice comes at the cost of worsening another.

Plant material such as wood, charcoal and crop waste burned directly as fuel, often for cooking and heating.

A line across a habitat along which organisms are recorded, either directly or using quadrats.

A device that changes the size of an alternating potential difference using primary and secondary coils linked by a magnetic core.

The movement of dissolved sugars and amino acids through phloem to parts of the plant where they are needed or stored.

The passing of a pathogen from one organism to another.

An electron microscope that transmits electrons through a thin specimen to produce a high-resolution image of its internal structures.

The loss of water vapour from a plant, mainly through pores in its leaves.

The continuous movement of water from the roots up the xylem to the leaves, replacing water lost by transpiration.

The transfer of cells, tissue or an organ into a recipient to replace damaged or missing material.

A system that carries substances between exchange surfaces and cells within an organism.

A wave whose oscillations are perpendicular to its direction of travel.

The overall direction of change in data, such as an increase, decrease or levelling off.

A lipid molecule made from one glycerol molecule chemically joined to three fatty acids.

A measuring wheel rolled along a route to measure its length.

Thyroid-stimulating hormone: a hormone released by the pituitary gland that stimulates the thyroid gland to release thyroxine.

A communicable disease caused by the bacterium Mycobacterium tuberculosis, usually affecting the lungs.

A mass of cells produced by uncontrolled cell division.

A machine with blades that rotates when driven by moving water, steam or air.

A condition in which the immune system destroys the insulin-producing cells in the pancreas, leaving the body unable to make insulin.

A condition in which blood glucose levels become too high because the body does not respond properly to insulin, and may not produce enough of it.

An approximate speed representative of an everyday activity or situation; individual speeds can be higher or lower.

The effectiveness of a contraceptive method in everyday use, including mistakes such as missed pills or incorrectly used condoms.

Electromagnetic radiation with frequencies above visible light but below X-rays. Exposure can cause sunburn, eye damage and an increased risk of skin cancer.

Forces acting on one object that combine to give a non-zero resultant force, changing its velocity.