Digest
- Evolution by natural selection takes place when some individuals survive and reproduce better than others in a particular environment and the heritable characteristics of a population change from one generation to the other due to that.
- Fitness is measured by the number of descendants left by individuals in a population.
- Evolution is not perfect: Evolved individuals might have characteristics that are suited to the environments of their ancestors but not so much to their current environments.
- Fitness is relative: evolved individuals can be the best fit for their current environments but not the perfect fit.
- Precise matches between an organism and its environment may equally be seen as constraints making such organism dependent on such specific environment.
Questions
- Does fitness depend on the number of offspring only and why?
- What is the ultimate fitness?
Digest
- At the heart of ecology lies the relationship between organisms and their environments. Fundamentally, this is an evolutionary relationship.
- Theodosius Dobzhansky, Russian-American biologist, said: "Nothing in biology makes sense, except in the light of evolution." This is also very true of ecology.
- Adaptation: "Organism X is adapted to live in environment Y" means that environment Y has provided forces of natural selection that have affected the life of X’s ancestors and so have molded and specialized the evolution of X. Adaptation means that genetic change has occurred.
- The theory of evolution by natural selection is an ecological theory.
- It was first elaborated by Charles Darwin in 1859.
- Its essence was also appreciated by his contemporary Alfred Russell Wallace.
- The theory of evolution by natural selection rests on a series of propositions:
- Individuals making up a population of a species are not identical
- Some variation among individuals is heritable
- Populations have the potential to populate the whole earth but they do not
- Different ancestors have different numbers of descendants
- Number of descendants an individual leaves depends crucially on the interaction between the characteristics of the individual and its environment
Questions
- Is evolution a theory in biology or ecology?
- What is the relationship between organisms and their environment?
