All the different plant populations make up the plant in this swamp. the plants are part of the bigger that contains many biotic and abiotic factors.

All the different plant populations make up the plant community  in this swamp. The plants are part of the bigger ecosystem, that contains many biotic and abiotic factors.

Explanation:

In ecological studies a community can be described as a different population of species that live in an area at a specific time. For example, different kinds of plants and animals living in an area at a particular time.

In ecological studies, an ecosystem can be described as a community possessing both its biotic and abiotic factors. For example, all the animals, plants, decomposers of a community along with abiotic factors like water, soil sunlight etc.

b. read the phase at the intersection of any given temperature and pressure.

that is wrong, its not thymus.