Growth rates of marine algae can be investigated using experimental mesocosms such as those shown.

Data are shown for percentage growth rates of red algae, grown in their natural environment and using mesocosms. The conditions investigated included competition from green algae and from elevated $\mathrm{CO}_{2}$, as well as competition from green algae combined with elevated $\mathrm{CO}_{2}$.

The diagram shows the greenhouse effect.

The diagrams below show different organisms (not drawn to scale).

Compounds of carbon, hydrogen and oxygen are used to supply and store energy.

In ecosystems, energy is used to convert inorganic compounds into organic matter. Energy enters ecosystems through producers.

Feeding relationships between organisms on rocky shores along the Pacific Coast of North America were studied. The food web shows the proportions of the total energy consumed by the two carnivorous species, a starfish (Pisaster ochraceus) and a small gastropod (Thais emarginata).