NEET BIOLOGY

Detailed explanation-1: -These tactic movements are in response to unidirectional light. Examples: Free swimming algae, zoospores, gametes when swim towards the diffused light are said to be positively phototactic and when they move away from the strong light, they are called negatively phototactic.

Detailed explanation-2: -Tropism is when a plant moves in response to an external stimulus in the environment. Positive tropism is when a plant moves towards a stimulus. Negative tropism is when a plant moves away from a stimulus.

Detailed explanation-3: -The movement of roots towards the pull of gravity is an example of positive geotropism, whereas the movement of plant stem in the direction opposite to the pull of gravity is an example of negative geotropism.

Detailed explanation-4: -An example of thigmotropism is the coiling movement of tendrils in the direction of an object that it touches. On the other hand, the folding movement of the Mimosa pudica leaflets, can be considered as an example of thigmonastism.