This chapter provides numerous examples of the main points. These examples are interesting and helpful at illustrating the concepts. In order to understand the concepts, it is helpful to read at least some of the examples carefully.
Adaptive explanations can focus on the proximate or the ultimate level.
Males cats that approach females in heat are more likely to sire offspring, thereby increasing their fitness. Natural selection is widespread, so we can expect that, in fact, many traits will have been shaped by natural selection and will therefore be adaptive. Organisms are not perfect. There is a trade-off between size and number, due to finite amount of resources that can be allocated to some combination of size and number. One might think it would be adaptive to get rid of the sepals, etc sooner than that, in order to conserve plant resources.