When two organisms interact, the impact is either positive, negative, or neutral. Ecologists have named the different combinations of interactions and we can explore these interactions using a chart:
Amensalism (0/-), cattle stepping on grass
Commensalism (+/0), birds that ride the backs of herbivores which kick up bugs
Competition (-/-), both deer eat same plant
Mutualism (+/+), anemone protects the clownfish while the clownfish protects the Anemone.
Predation & Parasitism (+/-), wolf eats deer or tick takes resources from deer
Neutralism (o/o), may not exist