physical substance that everything in the world is made of; not mind or spirit

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a living thing, especially one that is extremely small

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a particular group of people or animals living in a particular area

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developing or happening first; earliest

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an organism that produces organic compounds from simple substances such as water and carbon dioxide; an autotroph.

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the total amount of rain that falls in a particular area in a particular amount of time; an occasion when rain falls

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the light from the sun

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third in order, rank or importance

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the simplest and smallest forms of life. They exist in large numbers in air, water and soil, and also in living and dead creatures and plants, and are often a cause of disease.

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the animal and plant life of particular region

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complex molecules such as sugar or starch which provide the body with energy

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any animal that eats meat

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a part or element of a larger whole, especially a part of a machine or vehicle.

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to use something, especially fuel, energy or time

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a system that has no inputs from outside

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an organism, especially a soil bacterium, fungus, or invertebrate, that decomposes organic material.

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an animal which feeds on dead organic material, especially plant detritus.

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dead organic material

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all the plants and living creatures in a particular area considered in relation to their physical environment

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a situation in which a plant, an animal, a way of life, etc. stops existing

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an organism (= a living thing) that is similar to a plant without leaves, flowers or green colouring, and that usually grows on plants or on decaying matter. mushrooms and mildew are both fungi.

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all the waters on the earth's surface, such as lakes and seas, and sometimes including water over the earth's surface, such as clouds.

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divide (something) by passing or lying across it.

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the part of the Earth's environment where life exists

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extremely small living things that cannot be seen by naked eyes

(a)