Earth's largest ecosystems, biomes, are defined primarily by:

a. the seasonal variability in rainfall.

b. the average temperature.

c. the seasonal variability in temperature.

d. the average rainfall.

e. All of the above.

Answer: e. All of the above.

Explanation:

Rainfall, temperature, seasonal variability are the important factors which determines the type of vegetation will grow in a biome, the type of animals will adapt and survive. Also these factors also determine the fact that type of landforms will form over a region. These factors are necessary for the development of the biodiversity. A biodiversity can be define as the variability and variety of life forms that can be found in the ecosystem or biome.