Question

Microbial mats __________.

a. are the earliest forms of life on Earth

b. obtained their energy and food from hydrothermal vents

c. are multi-layered sheets of prokaryotes including mostly bacteria but also archaea

d. all of the above

Short answer

All statements are correct in the given options.

Step-by-step solution

Explanation

Microbial mats are the layers of prokaryotes formed some billions of years ago. This biofilm of prokaryotes includes the bacteria as well as archae. As the earlier earth was not evolved for the photosynthesis process, hence these prokaryotes in microbial mats were used to obtain their energy from the chemicals found near the fissures in the earth's surface called hydrothermal vents.

Final answer

Hence, the option 'd' with all of the above is correct.