Darwin failed to provide an explanation for which of the following?

Select the appropriate option for $Saltation$.

Industrial melanism is an example of what?

Identify $P, Q,$ and $R$ in the following descriptions of natural selection types:
$P -$ More individuals acquire peripheral character values at both ends of the distribution curve.
$Q -$ More individuals acquire mean character value.
$R -$ More individuals acquire value other than the mean character value.
$\quad\quad P \quad\quad\quad Q\quad\quad\quad R$

Which characteristic is responsible for an organism to survive in the environment,enable reproduction,and maintain genetic stability?

What is meant by the term 'Darwinian fitness'?