Symbiosis is a scientific term used to describe a close and long-lasting relationship between two different living organisms. In this type of relationship, the organisms involved often live in close physical proximity to each other and have evolved together over time. In many cases both organisms rely on each other for survival.

There are three main types of symbiotic relationships:

• Mutualism: In mutualistic symbiosis, both organisms involved benefit from the relationship. For example, certain species of ants and aphids have a mutualistic relationship where the ants protect the aphids from predators and in return, the aphids secrete a sugary substance called honeydew, which the ants feed on.
• Commensalism: In commensalism, one organism benefits from the relationship while the other is neither helped nor harmed. An example of this is the relationship between barnacles and whales. Barnacles attach themselves to whales and feed on small organisms in the water, while the whales are unaffected by their presence.
• Parasitism: In parasitic symbiosis, one organism, called the parasite, benefits at the expense of the other organism, called the host. Parasites often live on or inside the host organism, causing harm or inconvenience.

These symbiotic relationships are widespread and play important roles in ecosystems, influencing population dynamics, species distributions, and even the evolution of species.