Answer:
1. Parasitism (+/-)
2. Mutualism (+/+)
3. Commensalism (+/0)
Explanation:
In biology, symbols are often used to differentiate between different types of symbiosis - a certain relationship between organisms, which could be beneficial, harmful, or neutral.
To distinguish between parasitism, mutualism, and commensalism, biologists use the positive (+), negative (-), or neutral (0) symbols.
1. Parasitism (+/-)
One organism benefits from the other and the other one gets harmed. For example, the Gordian worm infects a cricket. It gets nutrients from the cricket and once it is fully grown and able to reproduce, it leaves the cricket's body. The cricket eventually dies. This indicates that the cricket doesn't receive any benefit, but the opposite.
+ gains (parasite); - loses (host)
2. Mutualism (+/+)
Both organisms benefit each other. For example, the algae and the coral. The corals provide protection and refuge, plus nutrients the algae need for photosynthesis and, in turn, the algae provides oxygen.
+ gains (coral); + gains (algae)
3. Commensalism (+/0)
In this relationship, one organism benefits the other while the other neither benefits nor is harmed. For example, the leopard shark and remoras. Remoras attach to sharks with the aim of travelling to further areas without spending energy and the leopard shark doesn't get harmed nor is benefited by the remoras.
+ gains (remoras); 0 not benefited, not harmed (leopard shark)
