1. discuss why reproductive isolation is necessary for divergence in populations.
3. identify the eight mechanisms of reproductive isolation.
4. explain the common ways in which sympatric speciation can occur.
5. recognize that allopatric speciation is the most common way in which new species arise.

1. Reproductive isolation is essential for population divergence. The mechanisms of reproductive isolation are essential for speciation which is the process of development of new species from preexisting species.

Due to reproductive isolation individuals of the same population will acquire different types of genetic variations and mutations such that males and females of the isolated populations cannot reproduce with each other.

3. Mechanisms of reproductive isolation are temporal isolation, behavioural isolation, gametic isolation, ecological isolation, mechanical isolation, hybrid inviability, hybrid sterility and hybrid breakdown.

4. Species populations within the same habitat become reproductively isolated in sympatric speciation. This speciation is a resultant of polyploidy where an offspring develops with twice the number of chromosomes.

5. Allopatric speciation is also called geographic isolation and it is the most common type of isolation. A geographical barrier separates individuals of  a species and the separated groups develop into new species.

organ system-an organ system is a group of organs that work together to perform one or more functions. each does a particular job in the body, and is made up of certain tissues.