Abiotic factors & species distribution

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A **non-living**, physical or chemical feature of a habitat — e.g. temperature, water, light, pH or salinity.

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A **living** influence on a habitat — e.g. predators, competitors, food or disease.

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**Temperature, water (moisture), light, pH and salinity** (also oxygen, wind, soil minerals).

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The **span of values** of an abiotic factor over which a species can **survive**; outside it, the species is absent.

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It is most **abundant** — conditions suit it best and its cell processes work well.

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The species is **absent** — the factor is too high or too low for it to survive.

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The one factor in **short (or excess) supply** that holds a species back and stops it living in a place.

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It sets the rate of **enzyme-controlled reactions**; extremes **denature** proteins, so a species is absent where it is too hot or too cold.

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Light is needed for **photosynthesis**, so plants are limited to places with **enough light** (e.g. not in deep shade or deep water).

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Too **little** water causes dehydration; too **much** can drown roots — so each species is restricted to a moisture range it tolerates.

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Name a specific **abiotic factor** AND give the **reason** for its effect — a bare list of factors only scores half.

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It lives only where the **abiotic conditions stay within its range of tolerance**; outside those limits it cannot survive.