Final answer:
In biology, an injection is the delivery of substances like vaccines or insulin into the body using a needle and syringe. Vaccines stimulate the immune system to prepare it against future encounters with the pathogen, while insulin injections regulate blood glucose in diabetics.
Step-by-step explanation:
The meaning of injection in the context of biology refers to the method of delivering substances directly into the body, typically using a needle and a syringe. In medical practices, injections are commonly used for the administration of vaccines, which are biological preparations that provide active acquired immunity to a particular infectious disease. A vaccine contains agents that resemble the disease-causing microorganism and is often made from weakened or killed forms of the microbe, its toxins, or one of its surface proteins. The agent stimulates the body's immune system to recognize the agent as a threat, destroy it, and keep a record of it so that the immune system can more easily recognize and destroy any of these microorganisms that it later encounters.
An example of an injection is the administration of insulin for people with diabetes. Insulin is a hormone produced by the pancreas that regulates the level of glucose in the blood. For individuals whose bodies do not produce sufficient insulin, injections of the hormone can be life-saving.