Animal behavior

definition, types of behaviour, reflex action, mechanism, example

1. Animal behavior Dambar Singh Khatri

2. All living organisms show some kind of reaction to the external environment. The reaction may be visible or automatic expression in response to stimuli. Stimuli may be chemical, physical or external substance, i.e. light, heat, radiation, sound, touch, gravity etc. The expression of organisms in response to the external environment is called behavior. The study of the behavior is called ethology.

3. Types of behavior Innate or stereotyped behavior: This type of behavior includes inherited mechanisms with which animals face the environment. The innate behavior is migration, leadership, mating, dominance etc. it is genetic behavior so it can be transmitted though generation to generation. Learned behavior: this kind of animal behavior is learned through the course of life cycle, i.e. form past experience. This kind of animal behavior is short lived and depends on the memory of organisms.

4. Reflex action The quick or immediate response toward stimulus is called r eflex action. This is automatic or involuntary action. The reflex action is also known as automatic response. In this response only a part of body is involved at a given time. It was first studied by Marshall Hall in 1883. There are many example of reflex action in human body, i.e. the blinking of eye, sneezing, hunger etc.In such actions, the impulses are carried by the sensory fibers from the receptor organ to the brain and back to the effector organ. The path or the route through which the impulses travel from the receptor is called a  reflex arc . Sensory nerves- from receptor to the brain. Motor nerves- From brain to receptor cells.

5. Mechanism of reflex action The center of reflex action is spinal cord. And it is controlled by central nervous system. The reflex action comprises four steps- reception, conduction, modulation and effect. The afferent fiber or sensory fiber enters the spinal cord through the dorsal root and carries the impulse from the effectors organ to spinal cord. The efferent fiber or motor fiber passes through the ventral root and carries impulses away from the spinal cord to the effectors organ. The adjustor neuron in spinal cord communicates between afferent and efferent neuron

6. Example: withdraw of hand from hot object On touching hot object unexpectedly, the heat or pain receptors in the skin are stimulated and nerve impulses are generated. Thus generated nerve impulse travel along the Dendron of the sensory neuron whose cell is located in the dorsal root ganglion and then along its axon to the spinal cord, where impulse is modulated. On reaching the grey matter of the spinal cord, the impulse passes from the sensory neuron to an interneuron across a synapse. Spinal cord sends impulse which travel through the axon of the motor neuron, the ventral root to the effector organ, the muscle(biceps). The impulse on reaching the arm muscles bring about its contraction, pulling the hand away from the hot object. The whole process takes place very fast. The involuntary and spontaneous action protects from damage due to heat.