Reason for fast speciation in present-day crop plants is:

1. Mutation

2. Isolation

3. Polyploidy

4. Sexual Reproduction

Forthcoming generations are less adaptive than their parental generation due to: 
1.  Natural selection
2.  Mutation
3.  Genetic drift
4.  Adaptation

Two opposite forces operate in the growth and development of every population. One of them is related to the ability to reproduce at a given rate. The force opposite to it is called:
1.  Fecundity
2.  Environmental resistances
3.  Biotic control
4.  Mortality