Behavior, like anatomy, may vary across individuals, be heritable, contribute to fitness, and therefore be susceptible to natural selection evolution.
Natural selection can act on behaviors as well as anatomical features. A behavior that is beneficial in the presence of predators or other dangerous animals can allow an individual to avoid being eaten. A behavior that increases the likelihood of survival and reproduction will tend to spread through a population, even if it is not necessary for every individual to perform it. This form of selection is called "selective pressure". Natural selection can also cause traits that are not necessarily beneficial to survive in the population long enough to produce offspring of their own. For example, males of many species compete with each other for access to females, and because these competitions can be very violent they often result in death. However there are cases where males who are more vulnerable to violence from other men have adapted ways to prevent themselves from being beaten up, such as by only fighting when they have the advantage or when there are no witnesses around. These techniques are called "defenses" against selective pressures. It is also possible for a male to lose a fight and yet still reproduce because he was the first to mate with the female after her partner died. This form of selection is called "sexual selection".
Animal Behavior Evolution Natural selection may be used to evolve behaviors that are governed by genes. If such actions improve fitness, they are likely to grow more prevalent over time. They are likely to become less prevalent if they lose fitness. The process by which these behaviors spread is called evolution.
Animal behaviorists have studied the behaviors of animals from bacteria to mammals to learn how and why they act as they do. This knowledge has helped scientists create better ways to manage and protect wildlife populations, and has also improved our understanding of human behavior.
Early researchers of animal behavior relied on natural observations to describe what animals do and why. But it was not until much later that scientists began to experiment with animals to see what behaviors would arise when they were placed in new situations. For example, psychologists have shown that animals will often try different approaches to find a way out of a problem situation, such as when their cage door is locked from inside. These experiments have helped us to understand how animals think and learn.
In addition to studying how animals behave, scientists have also tried to explain why certain behaviors are common or rare among species. They use this information to build theories about how and why animals differ from each other. For example, many birds will fight each other for territorial rights or food.
Because changes in behavior are considered to expose organisms to novel selection pressures and result in fast evolution of morphological, life cycle, and physiological features, behavior has been seen as a pacemaker of evolutionary change. Theoretically, if exposing individuals to new selection pressures could trigger evolutionary changes, then any aspect of an organism's environment could do so. Recent studies have shown that behavioral differences between species can be the result of natural selection and not just random events, providing evidence for this idea.
In addition to influencing what traits animals evolve, behavior also affects how they evolve. For example, behaviors such as migration or social grouping can influence which parts of an animal's genome are used by natural selection. These aspects of behavior can therefore play a role in determining an animal's evolutionary success or failure.
Finally, behavior can affect evolution by altering the rate at which organisms adapt to their environments. If most individuals in a population behave in a similar way, over time these behaviors will increase in frequency due to natural selection. This will reduce the ability of individuals to survive who differ from the majority behavior. Over many generations this will cause the evolution of a new behavior to occur more often than not. This is called "the drift problem" and is one reason why it can take so long for evolution to produce useful innovations - because we need rare mutations with large effects to overcome it.
Natural selection can lead to the evolution of behavior that is at least partially genetically controlled. Being governed by genes, however, is not the sole prerequisite for a behavior to evolve through natural selection. For example, a behavior may be under genetic control but be sensitive to environmental factors, such as learning behaviors.
Genes, via their impacts on morphology and physiology, form a framework within which the environment functions to define an individual animal's behavior. The environment can influence morphological and physiological development, and behavior develops as a result of the shape and internal workings of the animal. Morphology and physiology allow animals to cope with their surroundings; therefore, behaviors such as nesting or hunting spring up to help an organism deal with these pressures from natural selection.
The environment can also affect behavior through learning. An animal may learn what actions produce what results, allowing it to adjust its behavior accordingly. This is called "conditioning" and can occur in two ways: through direct experience (e.g., someone teaches an animal how to respond to a certain sound) or through indirect means (e.g., someone shows an animal how to respond to a certain sound). Direct experience tends to be more important than indirect experience in determining an animal's behavior. For example, a young bird might be taught by its parents how to find food, but this would not have much impact on its overall survival rate because other birds will copy this behavior. However, if a young bird learns from another bird that flying helps it get away from predators, then this would be an advantageous trait to have.
Finally, the environment can influence behavior via genetics. Genetic differences between individuals allow some people to be left-handed or right-handed, while others are forced to use either hand.
Natural selection results in adaptation, or a population dominated by creatures that are physically, behaviorally, and physiologically well suited to live and reproduce in a particular environment. Adaptation also implies that as environmental conditions change, the distribution of characteristics in a population might shift. This is because those individuals better able to survive and reproduce will do so, leaving behind offspring more like themselves.
For example, if the climate changes and it becomes warmer outside, then only animals capable of withstanding heat will be able to survive and reproduce. Over time, these heat-resistant organisms will dominate the population. Their offspring will also be resistant to heat, and so forth.
This process will continue until something stops it. Maybe the heat becomes too severe for any more evolution to occur (or maybe not), but either way, the result is the same: A population dominated by organisms best adapted to its surroundings.
Here's another example: If there is a poison in the water that affects both plants and animals, natural selection will cause plants and animals to evolve traits that allow them to survive in this contaminated environment. Some plants will be better at removing the poison from the water, while others will be less dependent on using photosynthesis to live and instead find other ways to get energy. Animals that eat these plants will also evolve to avoid consuming them, since doing so would mean being poisoned too.