Reproduction, Heredity, Variety in fitness of population, and variety in characters among the population are all four conditions for natural selection.
The necessary conditions for natural selection are as follows:
-That there is a variability among individuals (attribute or trait).
-There is a relationship between the attribute or trait and the efficiency of the individual who has that attribute or trait.
-That the attribute or trait can be inherited.
Explanation:
Natural selection is the interaction between phenotypes and the environment. Natural selection is the final consequence of the work of ecological processes. For natural selection to occur, the conditions explained above must be met. Finally, the natural selection process only occurs in common environments. It is not possible to measure the selection on two individuals who are in different environments, because natural selection facilitates the adaptation of an organism to its environment.
Yes, it is possible for a father and son to suffer from haemophilia. Most people who have hemophilia are born with it. It almost always is inherited (passed down) from a parent to a child.
