Question

Movements by pseudopodia of amoeba are due to change in
A. Pressure
B. Atmosphere
C. Temperature
D. viscosity

Answer 1

Hint: Amoeboid movement is a crawling-like type of movement and is the most common mode of locomotion noticed in eukaryotic cells. This is performed by extension of the cytoplasm of the cell. This type of movement is noticed in the cells or organism that do not possess any definite organs of locomotion.

Complete answer: Amoebas are unicellular protozoans that belong to the order Amoebida. They are composed of a mass of cellular fluid that is enclosed by a membrane. One or more nuclei can be found in these microbes as well as other cell organelles, such as food vacuoles. The movement of amoeba is known as amoeboid movement and is a type of crawling movement. The amoeboid movement are also used by some types of cells and unicellular organisms that have no set structures for mobility i.e. amoeboid movement can be applied to those with no set feet, fins, or wings and is involved in the formation of pseudopodia and posterior uropod.
The process of amoeboid movement operates by utilizing the cytoplasmic flow, or the force of the volume of fluid inside of the cell. This serves to pull the cell in the forward direction. Since the cell locomotory organ is its own, it essentially forms pseudopodia. The term pseudopodia means fake feet.
In order to produce the pseudopodia or little fake feet, the cytoplasm of the cell goes through the various biochemical changes. The biochemical changes are due to alteration of the viscosity or thickness of the fluid within different areas of the cell. So, it can be said that amoeboid movement is like rhythmic interactions which takes place between the viscosity or thickness of the cytoplasmic fluid in different areas of the cell.
When the cell starts to move in the direction it wants, the cytoplasm at that end of the cell becomes waterier than the cytoplasm which is called plasmasol. On the other side at the same time, the cytoplasm at the tail-end becomes thicker and forms a gelatinous version which is called plasmagel. This plasmagel builds a wall so that the more watery plasmasol can’t move towards it but can flow forward. This process is known as sol-gel theory proposed by Mast and Pantin.
The movements by pseudopodia of amoeba are results due to change in thickness or viscosity of the body fluids or the cytoplasm.

Therefore, the correct answer is option D. 

Note: Movement by pseudopodia or amoeboid movement is possible only over a hard surface. It depends upon the thickness of the plasmagel at the tail-end of the body which helps the plasmasol to move forward into the expanding pseudopodium. This process is called a sol-gel theory. According to sol-gel theory, due to a change in viscosity, the movements of amoeba by pseudopodia take place.