Mutations A.Gene 1. Base pair deletions, additions B. Chromosomal 1. Translocations Adaptation is constrained by mutation and gene flow, immigration of new genes, and the fact that the environment is always changing. A. Variations in climate B. Introduction of organisms C. Changes in predators or prey D. Change in diseases that are already present Natural Selection works on phenotypes- the observable traits of an organism. Different genotypes produce different phenotypes and embryology and development is affected by many environmental conditions.
Ecologists are interested in phenotypes like seed number, body size.
For example in the Galapagos ground finch, during a prolonged drought the birds that survived were those with large beaks that could crack both small and large seeds. Those birds with small beaks were at a disadvantage to utilize food and thus a larger proportion of birds with large beaks survived. Insecticide resistance is another example of selection.