perpheral membrane protiens
 
        
                    
             
        
        
        
Answer:
 Radiolabeled carbon atom in CO2
Explanation:
Photosynthesis is the process by which green plants fix the atmospheric CO2 into glucose. The process includes carbon fixation during which RuBisCo enzyme catalyzes the reaction of CO2 and a five-carbon compound called RuBP to form 3-phosphoglycerate (3-PGA). The 3-PGA enters the reduction phase of the Calvin cycle wherein it is reduced into glyceraldehyde 3-phosphate. Two molecules of glyceraldehyde 3-phosphate make one molecule of glucose. 
To test the hypothesis that glyceraldehyde 3-phosphate from photosynthesis is used by plants to synthesize lipids, radiolabeled CO2 must be used. The radiolabeled carbon atom in the CO2 would be fixed in the form of glyceraldehyde 3-phosphate. If the plant uses glyceraldehyde 3-phosphate as a precursor for lipid synthesis, the synthesized lipid molecules would carry the radiolabeled carbon atom. 
 
        
             
        
        
        
<span>10% rule (efficiency between trophic levels): limits how long an ecosystem's food chain can be
Predator/prey
cost benefit analysis (i.e. foraging) -- cost is risk of being eaten or
killed along the way, benefit is energy/nourishment obtained: limits
distribution of predator v. prey
Immigration/Emigration with other populations and ecosystems
Island
biogeography: size of land and distance from another
population/ecosystem (mainland): limits population size and variability
on island</span>