1st question on ADA practice exam is wrong

[theun4given]

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On the Sample Items from ADA, question #1 in bio is:

Organisms that obtain their energy from light can be termed:

they list the answer as A: autotrophic

I feel that this is wrong. The answer should be phototrophic because the "auto" part refers to the carbon source, not the energy. For example, a chemoautotroph is autotrophic but does not obtain energy from light.

your thoughts?

 

[D.D.S.]

I dont see an option for phototropic, so i woulda chose autotrophic. The light energy is what produces the ATP and NADPH which then goes to the calvin cycle where CO2 gets fixed into glucose and other stuff..

 

[theun4given]

exactly, "auto" just means the CO2 is not obtained by ingesting other organisms. It tells us nothing about the light making ATP and NADPH. The energy could have very well been made by inorganic oxidation instead and still have been autotrophic.

 

[D.D.S.]

au·to·troph

NOUN:

An organism capable of synthesizing its own food from inorganic substances, using light or chemical energy. Green plants, algae, and certain bacteria are autotrophs.

Autotrophs are catagorized into phototrophs (light energy, photosynthesis, etc), and chemotrophs (energy from oxidation, inorganic molecules, etc). But since the question doesnt have an answer choice of phototrophs, you would choose the next best answer which is autotrophs.

 

[theun4given]

Autotrophs cannot be unambiguously appointed as the next best answer. Heterotrophs is also one of the choices, and photoheterotrophs do exist. I am probably making a big deal out of a stupid little question.

 

[D.D.S.]

Heterotrophs do not directly obtain their energy from light.

 

[theun4given]

Sure they do. Check out the heliobacteria:

http://en.wikipedia.org/wiki/Heliobacteria