Question

Thigmotaxis is not shown by
A) Paramecium
B) Amoeba
C) Ascaris
D) Hydra

Answer 1

A change in direction of locomotion in a motile organism or cell which made in response to tactile stimulus (touch), and where the direction of movement is determined by the direction from which the stimulus is received. It may inhibit movement, causing the organism to come into close contact with a surface.

Complete Answer:
Thigmotaxis is commonly observed in insects.
- Paramecium on contact with hard objects, shows avoiding substances.
- Amoeba shows thigmotaxis as on coming in contact with solid substances, it generally changes its direction by using its pseudopodia.
- Ascaris do not show thigmotaxis as it is the internal parasite of humans. It is the most common worm for producing infection in humans.
- Hydra shows thigmotaxis as it is known to respond to a variety, both external and internal. On contact with a solid object other than prey, the whole body usually contracts rather rapidly.

So from the above discussion it is concluded that the right answer will be C as Ascaris has no ability to show movement by touching any substance.

Note: Thigmotaxis is an organism response to the stimulus of contact or touch. This response can be either positive or negative. An organism that is positively thigmotactic will seek contact with other objects, while one that is negatively thigmotactic will avoid contact.