Reflex and Complex Behavior, Biology tutorial


The study of animal behavior is termed as Ethology. Ethologists examine the methods and evolution of behavior. Charles Darwin discovered the scientific study of behavior and showed by numerous illustrations that behavior and also morphology and physiology, is an adaptation to ecological demands and can raise the chances of species survival.

Between the year 1930 and 1950, the Austrian naturalist Konrad Lorenz and the Dutch ethologist Niko Tinbergen found which certain animal's exhibit fixed-action patterns of behavior (FAPs) that are strong responses to the specific stimuli. For illustration, male stickleback fish attack other breeding males which enter their territory. The defensive male recognizes intruders through a red stripe on their underside. Tinbergen found that the male sticklebacks he was studying were so attuned to the red stripe that they would attempt to attack passing red British mail trucks visible via the glass of their tanks. Tinbergen named the red stripe a behavioral releaser, a simple stimulus which brings around an FAP.

Complex programmed behavior comprises some steps and is more complex than FAP. If birds build nests and beavers build dams they are showing complex programmed behavior.

Reflexes are as well innate behavior. A reflex is an inborn, simple, automatic response by a portion of the body to a stimulus. At its simplest, a reflex comprises receptor and sensory neurons and an effectors organ, for illustration, if certain coelenterates take out their tentacles. More complex reflexes comprise processing interneurons among the sensory and motor neurons and also specialized receptors.

Definition of Reflex:

Reflexes are involuntary, unlearned, simple responses to particular stimuli. Reflexes are controlled by the portion of the brain termed as the cerebellum, or primitive brain-animals don't have cognizant control over them. Illustrations of reflexes comprise shivering in response to the cold or blinking if an object flies in the direction of the eye.

At times it is hard to differentiate between reflexes and complex behavior. Complex behavior might be made up of some reflexes. For instance: Running, walking and jumping are all learned behaviors, however they comprise some reflexes such as those that control balance.

Complex Behavior Patterns:

Evolution, working on the four general methods explained by ethology, has produced an almost endless list of behavioral wonders through which animals seem nearly perfectly adapted to their world. Prime illustrations are the honey bees systems of navigation, communication and social organization. Bees rely mainly on the sun as a reference point for navigation, keeping track of their flight direction having respect to the sun and factoring out the effects of the winds that might be blowing them off course. The sun is a complex landmark for navigation because of its obvious motion from east to west; however bees are born knowing how to recompense for that. If a cloud obscures the sun, bees make use of the patterns of ultraviolet polarized light in the sky to find out the sun's location. When overcast vague both sun and sky, bees automatically switch to a third navigational system based on their cerebral map of the landmarks in their home range.

Animal and motivation:

Animal behavior is significant as a source of inspiration for all work comprising autonomous robots. Animals are capable to function perfectly in their atmosphere, and to adapt to changes in it. The models of animal behavior, both low-level models comprising individual neurons and high-level phenomenological models, can serve up as an inspiration for the growth of the corresponding behavior. Moreover, animals are usually experts in allocating the time in an optimal or near-optimal fashion to numerous activities (like eating, sleeping, drinking, fleeing and so on) that they should carry out in different situations, and lessons concerning behavior choosing in animals can give vital clues to the solution of identical problems.

Bottom-up approaches vs. black-box approaches:

As is the case with numerous different topics in science, animal behavior can be studied by using either a bottom-up approach or a top-down approach. The bottom-up approach can, in principle, lead to a more complete and detailed comprehending of the objects or organisms under study. Though, in sufficiently complex systems, the bottom-up approach might fail to give significant insights.

On other hand, a bottom-up study (that is, on the level of individual neurons) can reveal lots of significant features of simple systems, such as example: the much studied worm C. Elegans or the sea-slug Aplysia. The neural level is relevant as well in the field of autonomous, where simple behaviors are frequently implemented by using neural network architectures.

Nervous systems of animals:

In essence, the brain of vertebrates comprises of three structures namely, the forebrain, the midbrain and the hindbrain. The central nervous system (or CNS) comprises of the brain and the spinal cord. Moreover to the CNS, there is the peripheral nervous system, which comprises of the sensory neurons which carry information to the CNS and motor neurons which carry motor signals from the CNS to muscles and glands. The peripheral nervous system can be sub-divided to the somatic nervous system that deals by the external environment (via sensors and muscles) and the autonomic nervous system that gives the control of internal organs like the heart and lungs.

The autonomic nervous system is usually related with involuntary actions, like heart beat and breathing.

Moreover to the nervous system, there is a parallel system for feedback in the body of animals that is the endocrine system. The glands of the endocrine system discharge hormones (to the blood stream) which influence body and behavior. For illustration, elevated levels of the hormone angiotensin (whose source is the kidney) lead to the feeling of thirst, while adrenaline is comprised in fight-or-flight reactions (that is, fear, anxiety and aggression). Hormone discharge by the endocrine system is controlled either directly through the brain or by (that is, the levels of) other hormones.


Historically, various approaches to animal behavior were considered in Europe and USA. While European scientists, like the winners of the year 1972 Nobel Prize for medicine or physiology, Lorenz, Tinbergen and von Frisch, usually were concerned by the study of the behavior of animals in their natural atmosphere. In fact, the word ethology can be stated as the study of animals in their natural atmosphere.

By contrary, American scientists working by animal behavior usually performed experiments in controlled environments (example: a laboratory). This field of research is named comparative psychology. Both approaches have benefits and demerits: The controlled experiments taken out in comparative psychology let more rigor than the observational actions of Ethologists, however the behaviors considered in such experiments might, on the other hand, distinct strongly from the behaviors exhibited through animals in their natural environment.


Reflexes, the simplest forms of behavior, are involuntary reactions to the external stimuli. An illustration is the withdrawal reflex that is present even in much simple animals (and, obviously, in humans also). Though, even re-flexes exhibit a certain level of modulation. For instance, some reflexes show warm-up, meaning that they don't reach their maximum intensity instantaneously (an illustration is the scratch reflex in dogs). As well, reflexes might show fatigue, that is, a reduced, and finally disappearing, intensity even when the stimulus remains unchanged. Two evident reasons for fatigue might be muscular or sensory exhaustion, that is, either an inability to move or an inability to sense.

Kineses and taxes:

The other form of elementary behavior is the orientation of motion, either towards an object, substance or other stimulus, or away from it. In taxis, the animal follows a gradient in a stimulus like a chemical (or chemotaxis) or a light source (klinotaxis). Typical illustrations are trail following in ants, an illustration of chemotaxis, and the motion towards a light source through fly maggots: It is simple to comprehend how such klinotaxis takes place: the maggots compare the light intensity on each side of their bodies and can therefore estimate the light gradient. Motion towards the higher concentration (of food, for illustration), is exhibited even through very simple organisms, like bacteria.

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