Include prokaryotic autotrophs that float near the surface of water and are the basis of the food chain.

The correct answer is: Phytoplankton

Phytoplankton is an autotrophic organismthat lives in water and it is incapable of swimming against the water current. They can be found in all water systems, oceans, seas and freshwater basin ecosystems. Phytoplanktons are prokaryotic, usually single-celled organisms, bacteria or protists. The most common kinds are cyanobacteria, dinoflagellates, green algae, and coccolithophores.

A. Hole-punching the leaves- The purpose of hole punching the leaves is to make discs out of the leaves which are able to fit in into the syringe used in the experiment and which are also able to float

B. Adding bicarbonate buffer- Bicarbonate buffer is added as a source of carbon to leaves undergoing photosynthesis.

C. Exposing the disc to vacuum in the syringe - the leaves are exposed to vacuum in the syringe in order to remove or displace trapped air in the leaves so that the bicarbonate buffer can enter the interior of the leaves and the disc will then sink to the bottom of the syringe.

D. Adding a plain buffer- the plain buffer serves as the control experiment as it does not provide a carbon source for the discs in the experiment.

Explanation:

The floating disc experiment is used to demonstrate the process of photosynthesis in leaves. In the experment, the following procedures are followed:

A. Hole-punching the leaves- The purpose of hole punching the leaves is to make discs out of the leaves which are able to fit in into the syringe used in the experiment and which are also able to float

B. Adding bicarbonate buffer- Bicarbonate buffer is added as a source of carbon to leaves undergoing photosynthesis.

C. Exposing the disc to vacuum in the syringe - the leaves are exposed to vacuum in the syringe in order to remove or displace trapped air in the leaves so that the bicarbonate buffer can enter the interior of the leaves and the disc will then sink to the bottom of the syringe.

D. Adding a plain buffer- the plain buffer serves as the control experiment as it does not provide a carbon source for the discs in the experiment.

In the results of the experiment, the discs in the bicarbonate buffer will float as oxygen is produced during photosynthesis. However, the discs in the control remain at the bottom of the syringe as photosynthesis do not occur in the absence of a carbon source.