The functions as a gateway through which chemicals and small particles, such as enter or leave the cell. Substances may move through the membrane by (physical) processes, such as . Substances can also move through the membrane by (physiologicial) processes, such as .

cell membrane

such as water, micro-organism

physical process

simple diffusion, osmosis and filtration

such as potasssium permaganate in water,urea a liver waste diffuses from the body and the kidney help in filtering it out

physiological processs

active transport, phagocytosis and pinocytosis

such as soduim-potassium pump, exocytosis

Explanation:  transportation in and out of cell is done in different ways listed above but a barrier to this movement is the cell membrane which is an outer covering of the cell. it protect the cell and only some materials can penetrate the cell membrane e.g micro-organism, water e.t.c. the various physical and physiological processes are the various ways substance  cna be liquid, solid or gas are transported within or outside the  cell e.g food

i believe it's c. the trait for large beaks will be passed on to future generations through natural selection.

since eventually smaller beaks would have to find another source of food or even eventually just die out from the lack of food.