When Charles Darwin published the Origin of Species in 1859, his theory of natural selection set the stage for scientists to consider animal behavior in an evolutionary light. With this foundation, Konrad Lorenz, Niko Tinbergen, and Karl von Frisch began to seriously practice ethology, the study of animal behavior. In 1973, Tinbergen, Lorenz, and von Frisch shared the Nobel Prize.

Niko Tinbergen developed four questions that have been used ever since to model the study of animal behavior. The first question asks about the mechanisms of a behavior. What stimulates the animal to respond with the behavior it displays, and what are the response mechanisms? The second question concerns the translation of genotype to phenotype. How does an organism develop as the individual matures? As an individual grows from an embryo to an adult, what developmental processes allow the implementation of behaviors? The third question deals with the function of a particular behavior. Why is the behavior necessary for the animal's success and how does evolution act on that behavior? The fourth question examines the evolutionary history of a behavior. How has a particular behavior evolved through time? Can we trace a common behavior of two species back to their common ancestor? The first two questions are proximate questions: they are the "how" questions. The last two questions are ultimate questions: these are the "why" questions. Ultimate questions involve evolutionary and historical thinking.

In this SparkNote, we will first study instinctive aspects of behavior, both in terms of receiving information and responding to that information. Then we will look at more complex forms of reception and implementation, the cognitive process of learning. Next, we will see how animals communicate, sending information about themselves to other animals, and receiving information about other animals. Following that, we will learn about the ways in which animals orient in and navigate about their environments in response to the information they have received. Finally, we will explore the ecological aspects of behavior, including optimal strategies, kin relationships, and sexual behavior.