Question

The contractile vacuole present in amoeba is useful for (a) Ingestion (b) Locomotion (c) Both (a) and (b) (d) Excretion

Short answer

(d) Excretion

Step-by-step solution

Understanding the Contractile Vacuole

The Contractile Vacuole is an organelle in most unicellular organisms, such as amoeba. It plays a role in osmoregulation, specifically with expelling excess water. It is not involved in the processes of ingestion or locomotion

Matching the Function

Out of the given options, it is clear that the function of the contractile vacuole is neither ingestion nor locomotion, leaving the only possible answer to be excretion.

Key concepts

Osmoregulation in Amoeba

Osmoregulation in amoeba is a crucial biological process that allows the organism to maintain the appropriate balance of water and ions despite the changing environment. Amoebas live in freshwater environments where the water is hypoosmotic compared to their cytoplasm, which means that there is a natural tendency for water to flow into the cell due to osmosis. Without regulation, this influx of water would cause the amoeba to swell and potentially burst.

The contractile vacuole plays a central role in preventing this from happening. It acts as a bilge pump to expel excess water that enters the cell, actively collecting and then contracting to remove the water through the cell's membrane. By rhythmically expanding and contracting, the contractile vacuole effectively manages the water content inside the amoeba, demonstrating a form of excretion. This process is vital for the amoeba's homeostasis, which is the stability of its internal environment.

Unicellular Organisms

Unicellular organisms, such as amoebas, paramecia, and many types of algae, are composed of a single cell that performs all the functions necessary for life. Despite their simplicity, they are remarkably complex in their functionality. These organisms do not have the specialized systems found in multicellular organisms; instead, each cell must be able to carry out all life processes independently, including respiration, digestion, reproduction, and, importantly, excretion.

The contractile vacuole – present in many unicellular organisms – exemplifies how a single organelle can handle excretion and osmoregulation. In a single-celled context, the scope of excretion is not just about eliminating waste products from metabolic activities but also about regulating water content and ion concentrations to ensure cell survival. Unicellular organisms must be master regulators of their internal environments to thrive in various external conditions, making their survival mechanisms a captivating study in biological efficiency.

Excretion in Amoeba

In amoebas, excretion plays a dual role. It's not only about the removal of waste products generated from metabolic processes but also involves the regulation of fluid within the cell's internal environment. Here, the contractile vacuole is the star player. As we have established, it pumps excess water out of the cell, but it is also responsible for the expulsion of metabolic waste dissolved in that water.

Metabolic waste products such as ammonia are diffused into the vacuole, mixed with excess water, and expelled from the organism during the vacuole's contraction phase. This type of excretion is passive for solutes, relying on diffusion, but active for water expulsion, requiring energy. Although simple in structure, amoebas efficiently manage excretion, underlining the sophistication of even the most elementary forms of life and their ability to adapt to their environment.