What about symbiotic relationships are they not also types of heterotrophic nutrition in English

That's a great question that highlights an important distinction!

Symbiotic relationships are not a type of heterotrophic nutrition themselves. Instead, symbiosis describes the interaction or close association between two different species. Within these symbiotic relationships, one or both organisms might be heterotrophic, and their method of obtaining nutrients (heterotrophic or autotrophic) plays a role in how the symbiosis functions.

Here's the breakdown:

1. Symbiosis is a broad term for any close, long-term biological interaction between two different biological organisms. It includes:

   • Mutualism: Both organisms benefit (e.g., lichens, where fungi and algae live together). The fungus is heterotrophic, and the alga is autotrophic.
   • Commensalism: One organism benefits, and the other is neither harmed nor helped (e.g., barnacles on whales). The barnacle is heterotrophic.
   • Parasitism: One organism (the parasite) benefits at the expense of the other (the host). As we discussed, parasitic nutrition is a type of heterotrophic nutrition.

2. Heterotrophic nutrition describes how an organism obtains its food – by consuming other organisms or organic matter.

So, while a parasitic relationship is a type of symbiosis where the parasite uses heterotrophic nutrition to get food from its host, symbiosis itself is about the relationship, not the nutritional mode. Many symbiotic partners are heterotrophic, but the term "symbiosis" describes their living arrangement, not their feeding strategy.