Biology Test

Explanation
A cell can keep its necessary balance only within limits of environmental changes. This is because cells are highly sensitive to changes in their surroundings, such as temperature, pH levels, and nutrient availability. Any significant deviations from the optimal environmental conditions can disrupt the cell's normal functioning and lead to various cellular dysfunctions or even cell death. Therefore, maintaining a stable and suitable environment is crucial for a cell to maintain its necessary balance and ensure proper cellular processes.

Explanation
Homeostasis is a biological process that maintains a stable internal environment within an organism. This process involves regulating various factors, including the concentration of substances. It is true that the concentration of substances is not the same for a cell, tissue fluid, and blood. Each of these components has its own specific concentration levels that are necessary for proper functioning and homeostasis ensures that these concentrations are maintained within a certain range.

Explanation
A membrane that is permeable to a substance allows that substance to pass through it. In other words, the substance can move across the membrane freely without any restrictions. Therefore, the correct answer is "permeable."

Explanation
Diffusion refers to the gradual and even spreading out of molecules. It occurs when molecules move from an area of higher concentration to an area of lower concentration, resulting in a uniform distribution. This process is essential for various biological and physical phenomena, such as the exchange of gases in the lungs, the movement of nutrients across cell membranes, and the mixing of substances in a solution. Diffusion plays a crucial role in maintaining homeostasis in living organisms and is a fundamental concept in chemistry and biology.

Explanation
Substances actually diffuse from areas of greater concentration to areas of lesser concentration. This process is driven by the natural tendency of particles to spread out and achieve a state of equilibrium.

Explanation
Osmosis is the process of diffusion of water across a semipermeable membrane. It occurs when there is a difference in the concentration of solutes on either side of the membrane, causing water molecules to move from an area of lower solute concentration to an area of higher solute concentration. This movement of water helps to equalize the concentration of solutes on both sides of the membrane. Therefore, the correct answer is "diffusion of water."

Explanation
Contractile vacuoles are organelles found in certain organisms, such as protozoa, that help maintain a water balance in the cells. These vacuoles collect excess water from the cytoplasm and expel it out of the cell, preventing the cell from bursting due to osmotic pressure. By regulating the water content, contractile vacuoles help to maintain the proper functioning and shape of the cell. Therefore, contractile vacuoles are the correct answer to the question.

Explanation
Osmosis is a passive process that occurs spontaneously and does not require any energy or control from the cell. It is the movement of water molecules from an area of higher concentration to an area of lower concentration across a semi-permeable membrane. The cell membrane acts as a semi-permeable membrane, allowing water to freely move in and out of the cell through osmosis. Therefore, the cell does not have control over the process of osmosis.

Explanation
Active transport is the correct answer because it refers to the process in which the plasma membrane uses energy to move molecules against the concentration gradient, or diffusion pressure. This process requires the expenditure of energy to transport molecules from an area of lower concentration to an area of higher concentration. Endocytosis is the process of bringing molecules into the cell through the formation of a vesicle, while hypothesis does not relate to the movement of molecules. Lower transport is not a recognized term in biology.