Orientation responses in animals Taxis and Kinesis

Orientation movements Are of two kinds: Simple, short-distance movements that bring immediate benefit – either taxis or kinesis. Complex, long distance migratory movements which results from an internal motivation.

Taxes A taxis is a movement of an organism towards or away from a stimulus. Taxes are mainly confined to animals. Taxes usually require a more developed brain. They are named based on the kind of stimulus and the direction of the response. Complete BZ pgs 7-8

Examples of taxes Positive phototaxis Organisms move towards the light.

Negative phototaxis Organisms move away from the light.

Positive gravitaxis Organisms move towards gravity.

Negative gravitaxis Organisms move away from gravity.

Positive rheotaxis Organisms moving against a water current.

Positive thermotaxis Organisms move towards heat.

Positive chemotaxis Organisms move towards a chemical.

Kinesis (Comes from kinetic/movement) Kinesis is the orientation of an animal that results in change in rate of activity. Fast activity = unhappy, slow activity = happy. Kinesis is an animal's non-directional (random movement) response to a stimulus, for example humidity. The animal does not move toward or away from the stimulus but moves at either a slow or fast rate depending on its "comfort zone." In this case a fast movement means that the animal is searching for its comfort zone but a slow movement indicates that it has found it. Only requires a ‘simple’ brain to behave this way. The rate of movement in Kinesis is governed by the intensity of the stimulus, not the direction (remember that taxes is the movement towards/away from a stimulus). There are two kinds of kinesis: Orthokinesis Klinokinesis

Orthokinesis Orthos (Greek) = straight In orthokinesis, the intensity of the stimulus governs the speed of movement. It is the frequency of change from rest to movement. Examples of orthokinesis are seen in lampreys, which are more active in high intensities of light, and in cockroaches, which are more active in low intensities; flatworms and many kinds of fly larvae, among other invertebrates, exhibit orthokinesis.

Klinokinesis Klino (Greek) – to make bend A form of kinesis in which the frequency or rate of turning is proportional to stimulus intensity. Klinokinesis is well demonstrated by the movements of the wood louse. When wood lice are placed in dry air, they crawl about actively but without direction until they become gradually dehydrated. When the wood lice are placed in humid air, they move at first, but any activity they exhibited soon ceases and they become quiet. Wood lice placed in a container with dry air at one end and humid air at the other gradually congregate at the humid end. This transfer is achieved through what appear to be random rather than directed movements. Complete BZ pgs 5-6

Experiment example: Choice chambers Invertebrates such as slaters are able to respond to several different kinds of stimulus in their environment – humidity, temperature, light intensity. Choice chambers are used to find out which stimuli or stimulus an animal is responding to. Pill bugs (woodlice or slaters) are commonly used for these experiments looking at kinesis.

The difference between taxes and kinesis