Alternate forms of a gene for the same trait are called:

Passive transport refers to the movement of molecules across a biological membrane without the expenditure of cellular energy. This process occurs down the concentration gradient, meaning molecules move from areas of higher concentration to areas of lower concentration until equilibrium is reached. It includes simple diffusion, where small, non-polar molecules like oxygen and carbon dioxide can pass directly through the lipid bilayer of the membrane, as well as facilitated diffusion, where larger or polar molecules move across the membrane with the help of transport proteins, such as channel proteins or carrier proteins. Overall, passive transport is essential for maintaining the balance of molecules within cells and between different cellular compartments.

The cytoskeleton is critical to cellular motility, providing structural support and facilitating movement within the cell. It is a dynamic network of protein filaments and tubules that extend throughout the cytoplasm, giving the cell its shape, organizing its internal structure, and enabling various cellular processes. The cytoskeleton is involved in cell motility through the interaction of its components, such as actin filaments, microtubules, and intermediate filaments, with motor proteins that generate force and movement. Cytoskeletal elements are responsible for processes such as cell crawling, cell division, intracellular transport, and the maintenance of cell shape and integrity.

The cell wall is the part of a plant cell that acts as a barrier and provides support to the cell. It is a rigid, protective structure located outside the cell membrane and is composed primarily of cellulose, a complex carbohydrate. The cell wall gives plant cells their characteristic shape and provides mechanical support, preventing the cell from bursting due to osmotic pressure. It also helps regulate the movement of water and solutes into and out of the cell and protects the cell from pathogens and mechanical damage. In addition to cellulose, the cell wall may contain other polysaccharides, proteins, and lignin, depending on the type of plant cell and its function.

Contractile vacuoles are organelles found in some protists and single-celled organisms, primarily freshwater unicellular organisms. These vacuoles are responsible for regulating the water content of the cell by actively pumping excess water out of the cell. Contractile vacuoles collect excess water from the cytoplasm through a process of osmosis, where water diffuses into the cell due to differences in solute concentration between the cell and its environment. Once filled, contractile vacuoles contract rhythmically, expelling the excess water from the cell to maintain osmotic balance and prevent cell swelling or bursting. This process is particularly important for organisms living in hypotonic environments where water uptake is significant.