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BIO110 Evolution Through Natural Selection - OPEN University

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Open University

S103_1
4 Hours 

Level
Introductory

Course Home (Click Here)

Course Description

In this unit, 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.

Learning Outcomes

At the end of this unit you should know that:

  • By biological evolution we mean that many of the organisms that inhabit the Earth today are different from those that inhabited it in the past.
  • Natural selection is one of several processes that can bring about evolution, although it can also promote stability rather than change.
  • The four propositions underlying Darwin's theory of evolution through natural selection are: (1) more individuals are produced than can survive; (2) there is therefore a struggle for existence; (3) individuals within a species show variation; and (4) offspring tend to inherit their parents’ characters.
  • The three necessary and sufficient conditions for natural selection to occur are: (1) a struggle for existence; (2) variation; and (3) inheritance.
  • Endler's experiment with guppies demonstrated that evolution through natural selection can occur in relatively few generations.
  • Mutation is the ultimate source of variation.
  • The frequency of a particular character in a particular population may be due to chance events.


 

Introduction

  • Introduction Resource
  • In this unit, 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...

 

1 Charles Darwin

  • 1 Charles Darwin Resource
  • Charles Darwin (1809–1882) briefly studied medicine in Edinburgh before going to Cambridge intending to become an Anglican clergyman. Soon after the voyage of the Beagle (1831–1836), during which he was...

 

2 Darwin and natural selection

  • 2 Darwin and natural selection Resource
  • While Darwin knew nothing about the mechanism of inheritance, he was very aware of many other aspects of living organisms. Among these, three are particularly emphasized in his theory:

 

3 Natural selection in the guppy

  • 3.1 Introduction Resource
  • The purpose of this section is to consolidate your understanding of the theory of evolution through natural selection by looking at a specific example. The guppy (Poecilia reticulata) is a small fish whose...
  • 3.2 Number of progeny Resource
  • Female guppies begin to breed as soon as they become mature at about three months old; they then produce clutches of eggs, most of which become fertilized, at roughly one-month intervals until they die...
  • 3.3 The struggle for existence Resource
  • During their lives, guppies face a variety of environmental hazards which cause mortality. They must find food and, if food supply is limited, some will die through starvation. Heavy rain periodically...
  • 3.4 Variation Resource
  • Guppies vary in a number of characters; in particular, male guppies vary in the number, size and brightness of the coloured spots that decorate their bodies (Figure 2). This variation can be detected within...
  • 3.5 Inheritance Resource
  • The adaptive explanation for bright coloration in male guppies given above can only be correct, and can only have evolved by natural selection, if male coloration has a heritable basis. Direct evidence...

 

4 Other influences on evolution

  • 4 Other influences on evolution Resource
  • One of the crucial conditions for natural selection to occur is that there must be variation. However, it is extremely important to appreciate that natural selection does not itself cause that variation;...

 

5 Summary

  • 5 Summary Resource
  • By biological evolution we mean that many of the organisms that inhabit the Earth today are different from those that inhabited it in the past.

 

References and Acknowledgements

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Copyright 2007, by the Contributing Authors. Cite/attribute Resource. administrator. (2010, January 28). BIO110 Evolution Through Natural Selection - OPEN University. Retrieved March 13, 2010, from Free University Courses OCW Courses OpenCourseWare Freeversity Foundation Web site: http://freeversity.org/science-and-mathematics/biology/bio110-evolution-through-natural-selection-open-university. This work is licensed under a Creative Commons License Creative Commons License