How does a variation arise in a population

Population variability

learning goals

If you've worked through this page, you should

  • know what is generally understood by the term "variability",
  • can distinguish between genetic and modifying variability,
  • indicate the causes of the genetic variability,
  • be able to explain the importance of variability for evolutionary processes.
NRW curriculum

The students explain the influence of evolutionary factors (mutation, recombination, selection, genetic drift) on the gene pool of a population.

Variability is a driving force in evolution

Charles Darwin already recognized that the variability within a population is a decisive driving force in evolution. Animals and plants in a population look different and have different properties.

Due to their characteristics, some individuals are well adapted to the prevailing environmental conditions, others not so well. This is where selection comes in, the second important driving force of evolution. Those individuals who are well adapted to the environment not only have greater chances of survival for themselves, but they also have greater reproductive success, they are stronger, live longer, get by on less food, and so on, and can thus also produce more offspring who then inherit these traits and pass them on to their descendants. So heredity is another important factor that plays a big role in evolution.

Reading material

Read the following encyclopedia pages on my homepage so that you get a better understanding of the term "variability":

Thoughts on variability 1

"Genetic variability is crucial for the survival of a species" [1]

Thoughts on variability 2

"Another condition is, paradoxically, that the transfer of properties between the generations is not completely reliable." [2]

exercise 2

Assuming that the transfer of the properties from parents to children would be absolutely reliable, that is, without errors. Wouldn't all of the offspring of the parents then have to look identical, like identical twins? Explain why this assumption is wrong!

Find the solution here

Only through occasional mutations can new properties arise at all, which can then be used for selection. Many mutations are certainly disadvantageous for the individual, very few are advantageous. Most mutations, however, are "neutral", which means that they do not change the individual's chances of survival and reproduction.

Thoughts on variability 3

"The nature of biological variability, the primary source of evolutionary novelty, was the origin of some controversy that nearly buried Darwinism in the early 20th century." [2]

Task 3

Research What Darwin Knew About Variation Inheritance.

How could one understand the claim that the nature of biological variability nearly buried Darwinism in the early 20th century?

Find the solution here

Genetics made rapid advances in the 1920s to 1940s, and the contradictions that existed between the theory of natural selection and genetics were slowly resolving. The findings of genetics, especially population genetics, were integrated into Darwin's theories of evolution, and the modern synthetic theory of evolution emerged, which is still valid today because it has not yet been refuted.


  1. Savada, Hillis, Heller, Hacker: Purves Biologie, Springer Verlag Germany 2019, 10th edition. Edited by Jürgen Markl.
  2. Zrzavý, Jan; Burda, Hynek; Stork, david; Begall, Sabine; Mihulka, Stanislav. Evolution (German Edition) (p.26). Springer Berlin Heidelberg. Kindle version.