1 Most cases of COPD, and therefore emphysema, are caused by cigarette smoking. 2  Emphysema is rarely caused by a congenital condition known as Î±1-antitrypsin deficiency, for which there is a lab test. 3  Shortness of breath and cough are the main symptoms of emphysema.
Most plants, most algae, and cyanobacteria perform photosynthesis; such organisms are called photoautotrophs. Photosynthesis is largely responsible for producing and maintaining the oxygen content of the Earth's atmosphere, and supplies all of the organic compounds and most of the energy necessary for life on Earth.
Heterotrophs, unable to produce their own food, rely on the carbohydrates produced by photosynthetic organisms for their energy needs. Key Terms. photosynthesis: the process by which plants and other photoautotrophs generate carbohydrates and oxygen from carbon dioxide, water, and light energy in chloroplasts