Punctuated equilibrium and Gradualism

  • Explain how punctuated equilibrium is different from the gradual process of natural selection


Different species tend to evolve two different ways, one by punctuated equilibrium and the other by gradualism – these process can also occur at the same time. Gradualism occurs over longer periods of time and punctuated equilibrium usually occurs over a shorter period of time.

Gradualism is small and consistent changes over a long period of time where species develop small improvements which make them more suited to the environment. For example the horse slowly developing longer legs so it could run faster – these are micro evolutionary changes.

Punctuated equilibrium occurs when there are mutations in the genome of a couple of organisms in the species. These result in a noticeable and more sudden difference. For example if a all tigers didn’t have stripes, then a couple tigers were born with a mutation which gave the stripes. The tigers without stripes would be out competed since the stripped tigers can camouflage better hence it is easier for them to catch the prey. This would result in a rapid change where only stripped tigers would win – hence punctuated equilibrium. Scientists don’t know, whether tigers evolve dots by gradualism or punctuated equilibrium.

Fossil records and carbon dating (a technology to determine age of the fossils) have provided evidence of both gradualism and punctuated equilibrium occurring in the past.

The following graphs represent the difference between gradualism and punctuated equilibrium.


Punctuated equilibrium = rapid and large change in a species over short period of time

Gradualism = slow change in a species over a long period of time


Question 1.

Contrast and compare punctuated equilibrium and gradualism, using examples. [6 marks]

Question 2.

Explain what gradualism is? [2 marks]

Question 3.

Explain what punctuated equilibrium is? [2 marks]

Question 4.

Is the following graph an example of gradualism or punctuated equilibrium?

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