if someone told you they had discovered a new microscopic life form, tell me three characteristics that you would expect the life to possess.

there might be single celled  and very sensitive to change they might They are vitally important in the food chain and to the health of our planet.

not necessarily. higher fitness requires the organism to be reproductive successful. for example, an organism at age 10 with 15 offspring is much more fit than an organism at age 15 with only 5 offspring.