The ultimate energy of a food chain/pyramid comes from the sun.
The sun provides energy for plants, the primary producers, which are consumed by, and thus transfer energy, to the secondary consumers, which transfer energy to the tertiary consumers, and so on. When these organisms die, detritivores and decomposers break down the remains.
Answer:
It is known as a parasitic relationship.
Explanation:
Parasitic relationships are exactly what you described. We see these sorts of relationships in nature in worms for instance.
When a worm attaches to a host, it oftentimes leeches off the host's blood for nutrients and the like. In this manner, the worm benefits while the host gets weaker and loses nutrition.
Other examples include ticks and leeches.
