Answer: The role of an organism in the ecosystem is called its NICHE.
Explanation: The niche (pronounced 'neesh') of an organism is the specific function and purpose of the organism within its environment, ecosystem or food-web or food-chain.
Crossing over, or recombination, is the exchange of chromosome segments between nonsister chromatids in meiosis. Crossing over creates new combinations of genes in the gametes that are not found in either parent, contributing to genetic diversity.
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Interactions may be commensalism, mutualism, or parasitism.