A given ecosystem: biotic factors: kinds of living things characteristics: - number of species - dominance - species diversity Characteristics of a given ecosystem: soil: pH, humidity, ... climate: sunlight, precipitation, ... organisms: quantity, species, other ... Role of certain biotic and abiotic factors Types of relationships: living/living: commensalism, parasitism,... living/nonliving: plant, soil,... nonliving/nonliving: temperature, water, ... 19.