Tactic Movements.

Tactic movement

Tactic movement is a type of movement in plants and plant-like organisms where the entire organism moves towards (positive) or away (negative) from a stimulus.

Characteristics of tactic movement

1. The entire organism or cell moves in response to an external stimulus.
2. The movement can be towards the stimulus (positive tactic movement) or away from it (negative tactic movement).
3. It is not limited to plants but is also exhibited by certain plant-like organisms (e.g., Euglena) and even some animals.

Mechanism of tactic movement

1. A tactic is the process by which an organism moves from one place to another in response to an external stimulus.
2. This movement is a direct response to the stimulus, and the direction of movement is determined by the source of the stimulus.

Types of tactic movements (taxes)

Based on the nature of the stimulus involved, tactic movements are categorized as follows:

1. Phototaxis (Response to Light):
   • Movement in response to light.
   • Positive Phototaxis: Movement towards a light source.
     • Example: Euglena (a plant-like organism) moves towards light for photosynthesis.
   • Negative Phototaxis: Movement away from light.
2. Chemotaxis (Response to Chemicals):
   • Movement in response to chemical substances.
   • Example: In lower plants like Funaria, male gametes move towards chemical substances released by egg cells.
3. Geotaxis (Response to Gravity):
   • Movement in response to gravitational force.
   • Example: Movement of certain aquatic organisms towards or away from the bottom of a water body.
4. Aerotaxis (Response to Oxygen):
   • Movement in response to the presence of oxygen.
   • Example: Certain bacteria move towards higher oxygen concentrations.
5. Magnetotaxis (Response to Magnetic Field):
   • Movement in response to magnetic fields.
   • Example: Some bacteria orient themselves along Earth's magnetic field.
6. Rheotaxis (Response to Water Current):
   • Movement in response to water currents.
   • Example: Certain aquatic organisms orient and move against or along water currents.