Describe the three types of symbiosis and give mammal examples.

• A. Mutualism (both benefit, e.g., gut microbes aiding digestion in mammals), Commensalism (one benefits, the other unaffected, e.g., fur mites with little host impact), Parasitism (one benefits at host's expense, e.g., fleas, ticks).
• B. Parasitism is when both species benefit; mutualism is when neither benefits.
• C. Commensalism occurs when both benefit; mutualism occurs when one benefits; parasitism when none benefits.
• D. Mutualism is when one benefits at the other's expense; commensalism is when both benefit.

Answer: (A)

Symbiosis describes close, long-term interactions between two species, and the three classic types tell us who benefits. In mutualism, both partners gain something from the relationship; for mammals, gut microbes help digest complex foods and make vitamins, while the host provides a meal and a habitat. In commensalism, one partner benefits and the other is largely unaffected; an example you might see on mammals is certain fur-associated organisms that derive nutrients without noticeably helping or harming the host. In parasitism, one partner benefits at the expense of the other; fleas and ticks feed on blood, gaining nourishment while potentially harming the mammal host.

The correct description aligns each type with its benefit pattern and gives mammal-relevant examples for each, making it a clear and accurate answer. The other options mix up who benefits or reverse the relationships, which contradicts how these interactions work.