You radioactively labeled a red blood cell so that you could monitor its path through the heart. You see the labeled RBC in the right ventricle. Moments later, you see it in the aorta. How many heart valves must the labeled RBC have passed through during the monitoring

its d lol

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in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".

ecological efficiency: % of usable energy transferred as

biomass from one trophic level to the next typical is 10% efficient (90% of

energy is lost),is diagramed as the pyramid of energy flow. then osprey eagle

are tertiary consumer and the shrimp are primary consumer, so to balance

mass of shrimp (1/0.1) / 0.1 = 100 kg