Acquiring Energy #6: Heterotrophs, Autotrophs, Photosynthesis Graphs

Heterotrophs: Organisms that obtain energy by consuming energy-rich organic compounds of organisms and detritus (non-living material)

Autotrophs: Organisms that assimilate sunlight energy through photosynthesis or assimilate environmental inorganic chemical compounds through chemosynthesis Assimilate: Take in and convert energy/nutrients into form that organism can use for growth, maintenance, and other life processes Example: - Some Plants - Animals - Fungi - Bacteria/Archaea

Chemoautotrophs: Organism that takes inorganic chemicals and transforms it into energy Example: Bacteria/Archaea

Photoautotrophs: Organisms that carry out photosynthesis (sunlight energy, carbon dioxide, water converted into organic materials used in cellular functions) Example: - Plants - Bacteria/Archaea

First Section (increasing slope): - Light = limiting factor - Rate increases proportionately with increase in light intensity - Increase in rate = linear at lower light intensities

Second Section (flattening slope): - Light saturation - No further light will increase photosynthesis rate - Another factor has become limiting - Rate becomes constant - Either [CO2] or temperature needs to be raised to increase rate any further

Highest Point (y-axis): - Maximum rate of net photosynthesis

Highest Point (x-axis): - Light saturation point - Intensity at which additional increases in light do not increase photosynthesis

X-Intercept: - Light compensation point - Photosynthesis rate = respiration rate - Low light intensities above LC point = rate increases linearly to light intensity - Higher light intensities = departs from linearity to eventually achieve light saturation

Y-Intercept: - Respiration rate - Below 0

Sunflowers: - Can change: behaviour, leaf morphology, physiology (to improve low light photosynthetic efficiency) - Can NOT: increase carbon uptake to substitute for reduced solar energy