A scientific claim is based on logical reasoning and empirical evidence. Logical reasoning is done with the help of established theories and principles. Empirical evidence is collected from analysis of observations and experimentation results. In contrast, long tradition need not be scientific in nature. Many traditional activities are a result of word of mouth practice. Personal bias can also be not used to form a scientific claim since it is biased in one direction and can skew the judgement.
Photosynthesis makes the glucose that is used in cellular respiration to make ATP. The glucose is then turned back into carbon dioxide, which is used in photosynthesis. While water is broken down to form oxygen during photosynthesis, in cellular respiration oxygen is combined with hydrogen to form water.
Genetics play a key part in understanding evolution. While two organisms may bear similar or no resemblance whatsoever to each other, their genes can tell us whether or not they were related- and creatures that show change (especially dramatic change) show us evolution through genetics.
