In a random mating population in equilibrium, which of the following brings about a change in gene frequency in a non-directional manner?

Darwin in his 'Natural Selection Theory' did not believe in any role of which one of the following in organic evolution:

1. Parasites and predators as natural enemies

2. Survival of the fittest

3. Struggle for existence

4. Discontinuous variations

The most likely reason for the development of resistance against pesticides in insects damaging a crop is:

1. Genetic recombination

2. Directed mutations

3. Acquired heritable changes

4. Random mutations 

De Vries gave his mutation theory on organic evolution while working on:

1. Oenothera lamarckiana

2. Drosophila melanogaster

3. Pisum sativum

4. Althea rosea