Blank is not the only factor in determining the characteristics of an organism environment is also a major factor

Genes is not the only factor in determining the characteristics of an organism environment is also a major factor.

Explanation:

The organisms having the traits which are very favorable or suited in an environment have greater probability of surviving and reproducing at the higher rate than any organism which are less suited to that environment.When an organism start developing from one stage to another, the interaction of genes with the environment initiates at every moment of its life.The interaction of genes and environment determines the characteristics of that organism.

Yes he thought they should be left to chance why, because he thought that was the best thing to do