One of the most common symbiotic relationships is between various species of algae and fungi, or between cyanobacteria (commonly known as blue-green algae though it's not algae) and fungi. These paired species take the form of lichens. The term symbiosis was first used in the 19th century to describe the lichen relationship, which was thought to be highly unusual. Since then, we've discovered symbiosis is the norm, rather than the exception. In fact, it has shaped the evolution of most life on Earth. Symbiosis is almost everywhere we look Lichens are diverse. They grow on tree trunks, on roof tiles and on ancient rocks. The symbiosis of two different species allows both to survive in environments they might not be able to colonize otherwise. The fungus provides a suitable environment for its partnering species of algae or cyanbacteria to grow—it might otherwise be too exposed or dry, for example. In return, the fungus gets to share some of the carbohydrates produced by photosynthesis. This is an example where both partners benefit from their relationship. It's called mutualistic symbiosis. Lichens are often very good indicators of air quality and more general ecosystem health. Their absence can indicate poor air quality. Because they absorb air pollutants such as heavy metals they can be used as biomonitors. In another very common example of mutualistic symbiosis, most plant species live in a close relationship with fungi in the soil. It's known as a mycorrhizal association. The plants harness the energy in sunlight to make sugar from water and carbon dioxide in the process called photosynthesis. The plants share this food with the fungus, which relies on them for survival. In return, the fine threads of the fungus greatly increase the surface area of the plant roots for absorbing water and nutrients. Not all partners benefit Not all symbiotic relationships benefit both partners. In... |