The process of inducing any living organisms to show some response is called stimulation. The physical source which allow to show response is called source of stimulation.
The movement which is shown by an organism in response to the source of stimulus is called reaction.
|1||Light||Phototaxis||Positive||Movement of algae towards light|
|Negative||Movement of earthworm against light|
|2||Chemicals||Chemotaxis||Positive||Antherozoids of fern move Malic acid|
|Negative||Mosquitoes fly away from anti mosquito mat|
|3||Heat||Thermotropism||Positive||Opening of lotus in sun's heat|
|Negative||Closing of lilies during day|
|4||Gravity||Geotropism||Positive||Growth of roots into the ground|
|Negative||Growth of the shootsaway from the ground|
|5||Water||Hydrotropism||Positive||Movement of roots towards water|
|Negative||Sporangiospores of many molds grow away from a moist substratum|
|6||Contact||Thigmotropism||Positive||Whapping of tendrils of climbers|
|Negative||Collapsing of leaves of mimosa plant|
A response shown by different parts of a plant to any external stimulus is called tropism.
Animals respond to different stimuli. The response shown by an animal (or an organism) by moving towards or away from the stimulus is called taxis, e.g. when earthworm moves away from light, it is called negative photo taxis.
When an organism moves only a part of its body due to a stimulus, the response is called tropism. On the other hand, if the organisms moves as a whole due to a stimulus, it response is called taxis.
The response of an organism to light, either towards the source of light or away from it is known as phototropism. The movement of shoot of the plant towards light is called positive phototropism. When an organism responds to light by moving its whole body towards or away from light, it is called photo taxis. The movement of earthworm away from light is called negative photo taxis.
a. Chemo taxis: The responses shown by an organism to a chemical by moving its body towards or away from a chemical is called chemo taxis. For example mosquitoes move away from the mosquito repellant chemicals show in negative chemo taxis.
b. Hydrotropism: When an organism responds to water/moisture by moving a part of its body towards or away from water is called hydrotropism. For examples root of plants move towards water showing positive hydrotropism.
An earthworm when kept on the soil it moves inside the soil because of negative photo taxis. Earthworm moves away from the light showing negative photo taxis.
a. Closing of tulip flowers at low temperature- Negative thermo tropism
b. Movement of roots of germinating seedling towards the center of the earth- Positive geotropism.