Final answer:
In the tundra biome, an example of mutualism is the relationship between caribou and the gut microorganisms that help them digest cellulose, allowing the caribou to gain nutrients from a sparse and fibrous diet.
Step-by-step explanation:
Mutualism in the Tundra Biome
An example of a mutualism ecological relationship in a tundra biome would be between caribou or reindeer and the microorganisms in their gut. The caribou feed on the lichens and other vegetation that's sparse in the tundra region, while the microorganisms, which could consist of bacteria or protozoa, help break down the cellulose in the plants that the caribou eats. Like the herbivores in more temperate regions, these animals derive nutrients from a diet that would otherwise provide little energy due to its difficult-to-digest nature.
In this symbiotic relationship, the microorganisms obtain a secure habitat and a steady supply of food, while the caribou gains the ability to digest cellulose and access to the energy content of its fibrous diet, thereby enjoying improved nutritional value from the lichens and grasses. This kind of relationship is fundamental to the survival of many herbivorous animals and a key element in the tundra ecosystem's food web.