Download Natural selection at work File

Natural selection at work
http://www.techapps.net/interactives/pepperMoths.swf

Variation
occurs

The new feature /
characteristic now
dominates the former.

Increase in
population


‘Fittest’ survive
and reproduce
Original allele
frequency reduced


The new allele
frequency increases
Their gene/allele
frequency remains high

This variant survives
and reproduces


Environmental
change occurs
A different
variant is now
better suited
In natural selection, some of the population may die as a result of a change in the
environment, whatever the selective agent is. Those that survive, adapt to the new
environmental change because of beneficial mutations that allowed them to tolerate
the new change. These mutated genes will be passed on to next generations.
Two examples are peppered moth and mosquitoes.
Peppered moth: in a heavily industrialized regions, moth colour changed from white
to brown. A selective agent such as a bird can easily spot them against the white
lichen covering the trees. But when peppered moth cover a tree trunk that has been
blackened due to chemical pollution, then it is selected to adapt to the new change in
the environment.