The relationship between an alga and a fungus that makes up a lichen can be best characterized as mutualism and symbiosis. Here's why:
1. Mutualism: In this relationship, both the alga and the fungus benefit from each other. The alga provides food through photosynthesis, while the fungus offers protection and absorbs minerals from the environment. This mutual exchange of resources benefits both organisms.
2. Symbiosis: Symbiosis refers to a close and long-term interaction between two different species. In the case of lichens, the alga and the fungus live together in a mutually beneficial partnership, forming a new organism with unique characteristics that neither organism could achieve alone.
Therefore, the relationship between an alga and a fungus in a lichen is best described as mutualism (where both benefit) and symbiosis (a close interaction between different species).
