40 Ecology and Applied Environmental Science
Simple predation models have a strategic character. An essential qualitative result is that predation causes population sizes to oscillate, however it
does not generally cause extinction of one of the populations.
3.5 natural SElEction and Evolution
Evolution of a population is the total of successive alterations of the genetic
information, i.e. of the population’s hereditary characteristics’ changes.
A basic mechanism that causes evolution is natural selection that is the
differential reproduction of the genetic types. The genetic characteristics
of the population are not always reproduced according to their existing
frequency; some may be favoured and reproduced more, thus increasing the
frequency of their presence in the population.
An example of evolution observed in insects’ populations is their increased
tions under the pressure of mortality caused by the insecticide. The individuals of the insect population vary in relation to their resistance to the given
insecticide, and this variance has a genetic, and therefore hereditary, basis.
If the insecticide is applied, the most resistant insects have a greater probability for survival, and consequently for reproduction, that is, increased
fitness for the given environment that includes the insecticide. Thus, since
the hereditary quality of increased resistance will be transferred to more
and more descendants, the population will become more and more resilient,
with each successive generation, to the given conditions of the environment.
Another characteristic example is the continuous increase of the average
volume of the human brain, which was observed in paleontological findings.
In the human populations there was some variety in brain volume. Probably
the individuals with the largest brains were on average more capable of
using information, and this made them more capable of surviving, of finding
a mate for reproduction and raising children. Therefore the number of fertile descendants, that is, their fitness for the environment, was increased in
comparison to individuals with smaller brains. The result was the increase
of the average brain size of human populations during prehistoric periods.
We conclude from the above that natural selection acts only if genetic
variety pre-exists in the population. In populations without genetic variety,
no differential reproduction of genetic types is possible. Such a population
would find it hard to survive in the long run in an environment that would
change, given that it would not have the ability to make evolutionary adaptations in the changing conditions.
A basic mechanism that creates new genetic variety in the population is
mutation; that is, the accidental sudden alteration of the genetic information. Most mutations are harmful or even lethal, in which case they are
rejected by the natural selection mechanism and become lost because they
Simple predation models have a strategic character. An essential qualitative result is that predation causes population sizes to oscillate, however it
does not generally cause extinction of one of the populations.
3.5 natural SElEction and Evolution
Evolution of a population is the total of successive alterations of the genetic
information, i.e. of the population’s hereditary characteristics’ changes.
A basic mechanism that causes evolution is natural selection that is the
differential reproduction of the genetic types. The genetic characteristics
of the population are not always reproduced according to their existing
frequency; some may be favoured and reproduced more, thus increasing the
frequency of their presence in the population.
An example of evolution observed in insects’ populations is their increased
tions under the pressure of mortality caused by the insecticide. The individuals of the insect population vary in relation to their resistance to the given
insecticide, and this variance has a genetic, and therefore hereditary, basis.
If the insecticide is applied, the most resistant insects have a greater probability for survival, and consequently for reproduction, that is, increased
fitness for the given environment that includes the insecticide. Thus, since
the hereditary quality of increased resistance will be transferred to more
and more descendants, the population will become more and more resilient,
with each successive generation, to the given conditions of the environment.
Another characteristic example is the continuous increase of the average
volume of the human brain, which was observed in paleontological findings.
In the human populations there was some variety in brain volume. Probably
the individuals with the largest brains were on average more capable of
using information, and this made them more capable of surviving, of finding
a mate for reproduction and raising children. Therefore the number of fertile descendants, that is, their fitness for the environment, was increased in
comparison to individuals with smaller brains. The result was the increase
of the average brain size of human populations during prehistoric periods.
We conclude from the above that natural selection acts only if genetic
variety pre-exists in the population. In populations without genetic variety,
no differential reproduction of genetic types is possible. Such a population
would find it hard to survive in the long run in an environment that would
change, given that it would not have the ability to make evolutionary adaptations in the changing conditions.
A basic mechanism that creates new genetic variety in the population is
mutation; that is, the accidental sudden alteration of the genetic information. Most mutations are harmful or even lethal, in which case they are
rejected by the natural selection mechanism and become lost because they