Written by Merel Dagher (PEACE Advisor)
Which of the following has the trophic mode matched to its correct definition? (More than one may be correct)
a. photoautotroph – uses sunlight and carbon dioxide to obtain energy and carbon
b. photoheterotroph – uses sunlight and organic materials to obtain energy and carbon
c. chemoautotroph – uses inorganic substances and carbon dioxide to obtain energy and carbon
d. chemoheterotroph – uses organic molecules to obtain carbon dioxide and energy
e. all of the above
a. photoautotroph – uses sunlight and carbon dioxide to obtain energy and carbon
b. photoheterotroph – uses sunlight and organic materials to obtain energy and carbon
c. chemoautotroph – uses inorganic substances and carbon dioxide to obtain energy and carbon
d. chemoheterotroph – uses organic molecules to obtain carbon dioxide and energy
e. all of the above
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All of the above are correct. It helps to break the words apart. For example, photo is a prefix denoting the use of sunlight for energy. Autotroph is a suffix (and a word alone) used to denote a photosynthetic organism, which means carbon dioxide is used as the carbon source. Chemo is a prefix denoting obtaining energy from a source other than sunlight, so organic molecules or inorganic substances can be used. Heterotroph indicates the inability to produce one’s own food, so the carbon source can be acquired via organic molecules. Photoautotrophs and chemoautotrophs are found in all three domains. Chemoautotrophs are found the domain Archaea (and some bacteria). Photoheterotrophs make up some bacteria only.
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