EVERYDAY SCIENCE

Detailed explanation-1: -In unicellular organisms, diffusion across the cell membrane is sufficient for supplying oxygen to the cell (Figure 20.2). Diffusion is a slow, passive transport process.

Detailed explanation-2: -A single-celled organisms does not need specific organs for taking in food, exchange of gases or removal of wastes because the entire surface of the organism is in contact with the environment. Thus tha exchange of gases can take place by simple diffusion and there is no need of special organs.

Detailed explanation-3: -Unicellular organisms are one-celled and perform all the life process that are essential to maintaining the life of cell or organisms like nutrition, respiration, reproduction, excretion etc. Thus, the correct answer is option C.

Detailed explanation-4: -In unicellular (single-celled) organisms, diffusion across the cell membrane is sufficient for supplying oxygen to the cell. Diffusion is a slow, passive transport process. In order to be a feasible means of providing oxygen to the cell, the rate of oxygen uptake must match the rate of diffusion across the membrane.

Detailed explanation-5: -Cells can incorporate nutrients by phagocytosis. This amoeba, a single-celled organism, acquires energy by engulfing nutrients in the form of a yeast cell (red). Through a process called phagocytosis, the amoeba encloses the yeast cell with its membrane and draws it inside.