Behavior can be defined in various, generally unsatisfactory ways. In this chapter, behavior will be considered to constitute the responses of different organisms to stimuli coming from their external and internal environment, where these responses most often consist in the changes of their position or in the position and state of their organs. The integration of signals and storage of the information that directs an individual’s behavior is not performed at the genome level, but at the level of specialized organs or organ systems and, in animals, especially at the level of the neural system. Behavior is basically an integral compound of the organism’s phenotype. In some cases, it is quite difficult to distinguish the point where the individual’s traits (morphological, physiological or molecular) end and its behavior begins. Even the body color, i.e. the part of its phenotype that, at first sight, definitely belongs to the category of morphological attributes, can be (and in animals often is) a result of the behavior of the organism – for example, the seasonal changes in skin color in beach volleyball players or similar, only slightly more spectacular changes in chameleons, cephalopods and some fish. Comparing the morphological attributes to computer hardware and behavior to software may seem to be a useful analogy. The genotype of an individual during the ontogenetic process determines the attributes of the organism. The way the organism will handle these attributes, how is it going to use the organs that nature has given it during the ontogenetic process, i.e. how is it going to behave, depends on its software. The same morphological structure (hardware) may be used for completely different purposes – the same beak can be used with the same success for shelling seeds or breaking snails out of their shells; prehensile primate limbs are even more universal. While the hardware, i.e. the body structure, remains practically unchanged during the adult’s lifetime (at least if we ignore the manifestations of wear and tear), the software can develop continuously; the individual is able to change its behavior, for example, as a result of accumulated experience. It is obvious that components of behavior exist that, in principle, resemble software, e.g., learned patterns of behavior whereas others are more reminiscent of hardware, e. g. inherited fixed behavioral patterns.

I reserved a separate chapter for the evolution of behavior  mainly because some evolutionary mechanisms actually function, though not entirely, mainly in this area. On the other hand, the subject of cultural evolution, which would logically also belong to this chapter, is considered in a separate chapter (XVII).

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The classical Darwinian theory of evolution can explain the evolution of adaptive traits only in asexual organisms. The frozen plasticity theory is much more general: It can also explain the origin and evolution of adaptive traits in both asexual and sexual organisms Read more
Draft translation from: Evoluční biologie, 2. vydání (Evolutionary biology, 2nd edition), J. Flegr, Academia Prague 2009. The translation was not done by biologist, therefore any suggestion concerning proper scientific terminology and language usage are highly welcomed. You can send your comments to flegratcesnet [dot] cz. Thank you.