Food security is the ability of human populations to access food of sufficient quality and quantity.

The increase in human population and a concern for food security leads to a demand for increased food production.

Food production must be sustainable and not degrade the natural resources on which agriculture depends.

Agricultural production depends on factors that control photosynthesis and plant growth.

Increased food production will depend on factors that control plant growth, like

• breeding of higher yielding cultivars
• use of fertiliser
• protecting crops from pests, diseases, and competition.

All food production is dependent ultimately upon photosynthesis.

Plant crop examples include cereals, potato, roots and legumes.

Breeders seek to develop crops with

• higher nutritional values
• resistance to pests and diseases
• physical characteristics suited to rearing and harvesting
• the ability to thrive in particular environmental conditions

The area to grow crops is limited.

Livestock produce less food per unit area than crop plants due to loss of energy between trophic levels.

Livestock production is often possible in habitats unsuitable for growing crops.

Light energy is absorbed by photosynthetic pigments to generate ATP and for photolysis.

Light energy not absorbed is transmitted or reflected.

Absorption spectra of chlorophyll $a$ and $b$ and carotenoids shows the wavelengths of light absorbed by the different pigments in a leaf.