an ecosystem contains large numbers of living organisms
group_of_living_organisms is group_of_living_things. multicellular_organism is living_organism. animal is living_organism. earth has many_different_living_organisms microorganism is living_organism. group_of_animals is group_of_living_organisms. large_living_organisms_tend_to has more_mass_than_smaller_ones biome is ecosystem. population is group_of_living_organisms. aquatic_organism is living_organism.