biology

Shelford's law of tolerance

Shelford's law of tolerance is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Shelford's law of tolerance rather than just read about it. In short: Shelford's law of tolerance is a principle developed by American zoologist Victor Ernest Shelford in 1911. It states that an organism's success is based on a complex set of conditions and that each organism has a certain minimum, maximum, and optimum environmental factor or combination of factors that determine success.

Key takeaways

Shelford's law of tolerance belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Shelford's law of tolerance to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Shelford's law of tolerance from memory before moving on to harder problems.

Reference excerpt

Shelford's law of tolerance is a principle developed by American zoologist Victor Ernest Shelford in 1911. It states that an organism's success is based on a complex set of conditions and that each organism has a certain minimum, maximum, and optimum environmental factor or combination of factors that determine success. The further elaboration on the theory of tolerance is credited to Ronald Good.

Points out the second limitation of Liebig's law of the minimum - that factors act in concert rather than in isolation. A low level of one factor can sometimes be partially compensated for by appropriate levels of other factors. In case of chemical reactions it is known as law of limiting factor.

A corollary to this is that two factors may work synergistically (e.g. 1 + 1 = 5), to make a habitat favorable or unfavorable. Geographic distribution of sugar maple. It cannot tolerate average monthly high temperatures above 24–27 °C or winter temperatures below −18 °C. The western limit is determined by dryness, and this coincides with the western limits of forest vegetation in general. Because temperature and rainfall interact to determine the availability of water, sugar maple tolerates lower annual precipitation at the edge of its northern range (by about 50 cm). Good restated the theory of tolerance as: Each and every species is able to exist and reproduce successfully only within a definite range of environmental conditions. The law of tolerance, or theory of tolerance, is best illustrated by a bell shaped curve. The range of the optimum. Tolerance ranges are not necessarily fixed. They can change as: Seasons change. Environmental conditions change. Life stage of the organism changes. Example – blue crabs. The eggs and larvae require higher salinity than adults. The range of the optimum may differ for different processes within the same organism. Photosynthesis and growth in the pea plant

References

Worked examples

Example 1 — a first encounter with Shelford's law of tolerance

Start with the simplest possible case. Write down what Shelford's law of tolerance claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Shelford's law of tolerance before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Shelford's law of tolerance ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Shelford's law of tolerance

In research: Shelford's law of tolerance appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Shelford's law of tolerance in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Shelford's law of tolerance is common in secondary-school and first-year university syllabi. It links to neighbouring topics Ecological theories, Ecology stubs, so understanding it makes those chapters shorter.
In everyday life: Look for Shelford's law of tolerance outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Shelford's law of tolerance in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Shelford's law of tolerance means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Shelford's law of tolerance out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Shelford's law of tolerance in simple terms?

Why does Shelford's law of tolerance matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Shelford's law of tolerance?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Shelford's law of tolerance.