What term describes diffusion across a biological membrane requiring no cellular energy?

The circulatory system is responsible for transporting oxygen molecules to different locations throughout the body. Oxygen is crucial for cellular respiration, the process by which cells generate ATP (adenosine triphosphate), the energy currency of the cell. In the circulatory system, oxygen is transported by red blood cells, which are specialized cells that contain the protein hemoglobin. Hemoglobin binds to oxygen in the lungs, where oxygen concentration is high due to inhalation, and releases it in tissues where oxygen concentration is low due to cellular respiration. This process ensures that oxygen is efficiently delivered to all cells in the body for their metabolic needs.

The aerodynamic nature of a bird's wing is an example of the central theme in biology known as "Structure and function." This theme emphasizes the relationship between the form and function of biological structures. In the case of a bird's wing, its structure, including its shape, size, and arrangement of feathers, is intricately related to its function, which is to provide lift and thrust for flight. The specific structure of the wing, such as the curvature of the airfoil shape, enables it to generate lift by creating a pressure differential between the upper and lower surfaces of the wing when air flows over it. Thus, the structure of the wing is adapted to its function of facilitating flight in birds.

The magnification of a standard ocular lens on a light microscope is typically 10X. The ocular lens, also known as the eyepiece, is the lens closest to the observer's eye. It magnifies the image produced by the objective lens, which is the lens closer to the specimen being observed. Together, the ocular lens and the objective lens determine the total magnification of the microscope. The standard ocular lens provides a magnification of 10X, meaning it magnifies the image by a factor of 10 compared to the naked eye.

The slide, containing the specimen to be observed, is placed on the stage of a light microscope. The stage is a flat platform located beneath the objective lenses and above the light source. It typically has a mechanical stage control that allows precise movement of the slide in both the x-axis (side to side) and y-axis (front to back). The stage clips or a stage holder secure the slide in place during observation, ensuring that the specimen remains in focus under the objective lenses.