Are lichen animal, mineral or vegetable

A. They are actually living creatures drawn from up to three different 'kingdoms'.

Q. Kingdoms

A. Yes, the natural world, at the broadest level, can be divided into five different groups or kingdoms.

Living organisms are classified into these kingdoms according to cell structure, number of cells, food source and movement. The five kingdoms are plant, animal, moneran, fungus and protist.

Humans belong to the animal kingdom.

Q. And which ones do lichen belong to

A. They are living structures that are made up a fungus and either a member of the Protista Kingdom or Monera Kingdom. The main difference between Protista and Monera organisms, which are both single-celled, is that the former has a nucleus and the latter doesn't.

Q. Why more than one

A. Lichen - such as the flavoparmelia caperata shown under a microscope on our home page - are the result of a mutually beneficial relationship between two different organisms. The fungus 'farms' algae for food, while the algae uses the water absorbed by the fungus to make the food, which it also uses.

Q. Where do lichen live

A. Normally they grow on exposed rocks or trees. It seems that nowhere is too hot or too cold for them: they're found in both deserts and tundra.

Q. How many species of lichen are there

A. About 17,000 and that's only the ones we know about, there could be more.

Q. How fast do they grow

A. Very slowly, but given enough time they can make it up to several metres across. Some lichen can live for 1,000 years.

Q. Can lichens be used for anything

A. Yes, where there's little else on offer they make an important meal for animals. The 'manna' described in the Bible, which kept the Jews from starving while in the wilderness, is thought to be a lichen.

They have also been commercially used as dyes, medicines (thanks to their antibiotic properties), poisons, cosmetics and perfumes; and are good indicators of pollution.

Do you have a question about the classification of the natural world Ask The AnswerBank here.

by Lisa Cardy