• Video
  • 5 mins
  • Level 1: Introductory

Darwin and ecology

Updated Thursday 5th March 2009

Jonathan Silvertown of The Open University and the Evolution Megalab considers the interaction between ecology and evolution - and what we can learn from thrushes and banded snails.

Watch

Copyright The Open University

Read

Darwin saw the ecological relationships between species being the source, or one of the sources, of selection pressure. That’s where the struggle for existence happens; it happens between species and between individuals in an ecological context. So a 20th Century biologist described the situation as there being an evolutionary play inside an ecological theatre - and there are lots and lots of examples.

A favourite one of mine would be the evolution of the banded snail. This is eaten by thrushes. Thrushes search for these things and, when they find them, they typically take the snails to a particular stone within their territory, called an anvil, and they beat the hell out of the snail and the shell breaks off and then they eat the snail inside. You can look at what the thrushes have been eating by looking at the remains around these thrush anvils.

And, what’s nice about this banded snail is, actually, it varies a lot in its shell colours and patterns, and so experiments have been done using the remains found around the thrush anvils and this sort of thing, which demonstrate that the patterns of these banded snails are adaptive, and the snails that are more cryptic, that are more difficult to find, appear, are eaten less often, turn up at anvils dead less often than the ones that are more conspicuous.

And this is, basically, a selection process going on, natural selection, where the agent of natural selection, the thing doing the selection if you like, is the thrush in its predation.

Why are there so many species? Well we know these species evolve through natural selection, but it’s not obvious how natural selection alone would produce these species. And the reason for this is the following: that natural selection favours those individuals that breed the most often. Different species occupy different niches, that is to say different roles in what Darwin described as “the economy of nature”, or what we’d describe today as ecology. They have different ecological roles.

So these could be different positions in the food web, so there are plants and there are things that eat plants, there are things that eat the things that eat plants, and so on. And there are many different ways of being a plant and being a herbivore, and there are different ways of capturing your food if you’re a carnivore, and these are the different niches, they’re like the roles in an economy, hence Darwin’s term “the economy of nature”. And that is the answer to why there are so many species when you combine it with natural selection, so that’s another way in which ecology and evolution are counterparts and have to be seen as different aspects of the same thing.

Darwin's influence

Darwin's influence was felt widely. Open University experts share how he helped shaped their disciplines.

 

For further information, take a look at our frequently asked questions which may give you the support you need.

Have a question?

Other content you may like

Extract from Origin Of Species Copyrighted image Icon Copyright: BBC article icon

History & The Arts 

Extract from Origin Of Species

In 1859 Darwin published a book that was to change the way in which we all viewed the world. "On the Origin of Species" was to bring this quiet man a fame that he was to shun for the rest of his days. The theory of natural selection deals with the way in which species are selected to survive by nature. Any advantage, be it the right shaped beak or a long neck, will tend to be developed by the evolutionary process. Hence the giraffe or the kangaroo or even humans have evolved a variety of ways and means that give them an advantage over other species. The following is an extract from a chapter in Darwin’s book entitled: "Natural selection".

Article
Evolution through natural selection Copyrighted image Icon Copyright: Used with permission free course icon Level 1 icon

Nature & Environment 

Evolution through natural selection

In this free course, Evolution through natural selection, we describe the theory of evolution by natural selection as proposed by Charles Darwin in his book, first published in 1859, On the Origin of Species by Means of Natural Selection, or The Preservation of Favoured Races in the Struggle for Life. We will look at natural selection as Darwin did, taking inheritance for granted, but ignoring the mechanisms underlying it.

Free course
4 hrs
Origin Day Lecture: Audience Question One Copyrighted image Icon Copyright: British Council video icon

History & The Arts 

Origin Day Lecture: Audience Question One

What would have happened had The Origin of Species never been published?

Video
5 mins
Darwin, 'The Origin' and the future of biology Copyrighted image Icon Copyright: British Council video icon

History & The Arts 

Darwin, 'The Origin' and the future of biology

On the 150th Anniversary of the publication of Charles Darwin’s On the Origin of Species, Professor E O Wilson, considered by many as Darwin’s natural heir, gives his assessment of the master naturalist, Darwin’s big idea and his own vision for a new system of biology equipped to tackle the threats to our natural world.

Video
15 mins
OU Lecture 2009: Developing natural selection Copyrighted image Icon Copyright: OU image library video icon

TV, Radio & Events 

OU Lecture 2009: Developing natural selection

Professor Richard Dawkins discusses Darwin’s peers and the development of the theory of Natural Selection.

Video
10 mins
OU Lecture 2009: Darwin and Wallace Copyrighted image Icon Copyright: OU image library video icon

TV, Radio & Events 

OU Lecture 2009: Darwin and Wallace

Dawkins discusses the ideas of Blyth, Matthew, Wallace and Darwin and begins to explore neo-Darwinism.

Video
10 mins
OU Lecture 2009: Download the lecture Copyrighted image Icon Copyright: OU image library audio icon

TV, Radio & Events 

OU Lecture 2009: Download the lecture

The full lecture to download as an mp3.

Audio
30 mins
OU Lecture 2009: Solving the riddle Copyrighted image Icon Copyright: OU image library video icon

TV, Radio & Events 

OU Lecture 2009: Solving the riddle

Random chance, design or cumulative natural selection? Dawkins explores how Darwin and his peers solved the riddle of life.

Video
10 mins
Darwin and biology Copyrighted image Icon Copyright: Production team video icon

History & The Arts 

Darwin and biology

The Open University's David Robinson considers Darwin's continuing influence on Biology as an academic discipline, including the "Out of Africa" hypothesis with regard to human evolution.

Video
5 mins