Final answer:
Motility encompasses the movement of a cell/organism through an environment, movement past a cell, internal cell component movement, and cell size or shape changes. Flagella, cilia, and pseudopodia are among the structures enabling motility, which also includes directed movement like taxis.
Step-by-step explanation:
Motility refers to the capacity of an organism or cell to move. Flagella and cilia are commonly involved in motility, aiding in the movement of cells or organisms through their environments. Flagella enable a whip-like or rotary action, facilitating propulsion, while cilia, being shorter and more numerous, beat in a coordinated manner to swim or move fluids. Additionally, some cells utilize pseudopodia, which are temporary cytoplasmic extensions, for movement or to engulf food. Moreover, motility can also include internal movement such as cytoplasmic streaming within cells, which helps transport materials when diffusion is inadequate, especially in larger cells.
Therefore, motility can be defined as:
- Movement of a cell/organism through its environment
- Movement of the environment past a cell (such as cilia moving mucous)
- Movement of components within a cell (like organelles during cytoplasmic streaming)
- Changes in the shape or size of a cell, such as during engulfing of food or cellular locomotion
Taxis, another form of motility, is the directed movement towards or away from a stimulus; for example, phototaxis is movement towards light.
Given the above information, the answer to the student's question would be 'E) All of the above are correct.'