Answer:
Mechanical barriers — which include the skin , mucous membranes , and fluids such as tears and urine — physically block pathogens from entering the body. Chemical barriers — such as enzymes in sweat , saliva , and semen — kill pathogens on body surfaces.
Answer:
the process by which green plants and some other organisms use sunlight to synthesize nutrients from carbon dioxide and water. Photosynthesis in plants generally involves the green pigment chlorophyll and generates oxygen as a by-product.
The answer is signal transduction. It is also known as cell signaling. It is the transmission of molecular signals beginning from a cell's exterior to its interior. Signals got by cells must be transferred efficiently into the cell to make certain a suitable response. This step is started by the cell-surface receptors.
