What are the two main food webs on earth?

There isn't a simple division of Earth's food webs into just two main types. Instead, food webs are incredibly diverse and interconnected, with many overlapping and interconnected networks.

However, if we broadly categorize based on primary energy source, we can identify two major categories:

1. Terrestrial food webs: These webs are driven by photosynthesis, where plants and some microorganisms capture sunlight and convert it into energy. This energy flows through herbivores that eat plants, then to carnivores that eat herbivores, and so on.

2. Aquatic food webs: These webs are driven by chemosynthesis in some cases, where bacteria use energy from chemicals like hydrogen sulfide to produce organic matter. However, the majority of aquatic food webs are based on photosynthesis, with phytoplankton (microscopic algae) playing a vital role. These primary producers are consumed by zooplankton, which are then eaten by larger animals, leading to complex food chains within the aquatic environment.

It's important to remember that:

* These categories are not absolute. Many organisms exist in both terrestrial and aquatic environments, contributing to multiple food webs.

* Food webs are constantly changing based on environmental factors, interactions between species, and the availability of resources.

Rather than thinking in terms of just two main food webs, it's better to understand that Earth's food webs are a vast, interconnected network that supports all life on the planet.