Which of the following is the most important precondition for speciation to occur?

(1) Reproductive isolation

(2) A crash of the population size

(3) Adaptive radiation

(4) Random mating

What does the term 'reproductive isolation' refers to?

(1) An individual is unable to fertilise itself 

(2) Genes are not exchanged between two populations

(3) Individuals from two populations never mate

(4) Individuals form two populations never produce offsprings

One of the important consequences of geographical isolation is:

1. no change in the isolated fauna

2. preventing speciation

3. speciation through reproductive isolation

4. random creation of new species