Prairie dogs dig extensive series of tunnels. beavers build dams that alter the hydrologic profile of an area. what sort of organisms are prairie dogs and beavers?

The mentioned species are ecosystem engineers.  

An organism that substantially amends, creates, destroys or maintains a habitat is known as an ecosystem engineer. These species can exhibit a huge influence on the landscape-level heterogeneity of a region and the species richness.  

The dams created by beavers help in monitoring the quality and quantity of water downstream that are used by both humans and animals. Their flooded regions and ponds develop habitat for various animals and plants like birds, fish, amphibians, and insects.  

The prairie dogs develop burrows required by the birds and snakes, they are the tasty meals for the predators, and even assist to mow the lawn that motivates the new development and plant diversity.  

the answer is 1. photosynthesis. glad to