Evolution by Roger Abrantes
The fundamental principles: evolution by means of natural selection, variation, selection, fitness, evolutionarily stable strategies.
This is, probably, the best and the shortest introduction to evolution that you can read. It is essential reading for all students of animal behavior and animal trainers. Without understanding evolution, we cannot expect to understand why animals developed the behavior they display.
Chapter 1 Evolution by means of natural selection.
Chapter 2 The origin of life and the origin of species.