What about this? Condoms stop seamen and sperm entering the woman.
Other examples of the institute's annual crop of examination howlers include:
A 60-foot tree can break wind for up to 200 yards.
A sexually transmitted disease is gonorrhoea, the penis becomes inflammable.
People should not serve in food shops if they are deceased in any way.
After sewage effluent has been treated, it is used to make toilet water.
Lead makes you sterile - it is an anti-knocking agent.
You put your finger into an agar plate, put it into an incubator and leave it there for a week.
The institute would welcome more howlers for its next compilation, and is particularly interested in diagrammatic ones which illustrate biological confusion.
And finally, just to satisfy the kill-joys, the institute would like to hear from any teachers who have used howlers constructively with their class.
Institute of Biology, 20-22 Queensberry Place, London SW7 2DZ