Photosynthesis

Definition

The metabolic process by which photopigment-bearing autotrophs convert light energy into chemical energy stored in organic compounds, primarily carbohydrates. In oxygenic photosynthesis—characteristic of plants, algae, and cyanobacteria—light-driven water splitting generates oxygen as a byproduct while producing ATP and NADPH to fix carbon dioxide. This process underpins nearly all terrestrial and aquatic food webs, directly or indirectly supplying the energy that sustains heterotrophic organisms including insects and arachnids.

Etymology

From Greek phōs (light) + synthesis (putting together), coined in the late 19th century to describe the light-dependent construction of organic matter.

Example

Aphid populations on a leaf depend entirely on the photosynthetic output of their host plant; the carbohydrates produced via photosynthesis are transported through phloem sap, which aphids tap to obtain sugars and amino acids. Similarly, web-building spiders in agricultural fields indirectly track photosynthetic productivity, as their prey biomass correlates with plant-mediated energy capture.

Synonyms

• oxygenic photosynthesis
• photoautotrophy
• carbon fixation (in context)

Related Terms

• Autotroph
• chloroplast
• chlorophyll
• cellular respiration
• Trophic level
• Primary production
• phloem
• herbivory
• Symbiosis
• cyanobacteria

Usage Notes

Specialists distinguish oxygenic photosynthesis (water as electron donor, O₂ released) from anoxygenic photosynthesis used by some bacteria (sulfur compounds or other donors, no O₂). The term is sometimes misapplied to any light-driven biological process; strict usage reserves it for carbon-fixing metabolism. In entomological contexts, photosynthesis is rarely the direct subject but is the essential backdrop for understanding plant-insect nutritional ecology, including phloem-feeding, leaf-mining, and gall-forming lifestyles.