Variations within species are the result of and .

Variations within species are the result of mutations and genetic shuffling.

Explanation:

Mutations arise from any changes which occur in the DNA of an organism. Most mutations can be heritable whereas there are some mutations which are not heritable. Mutations can cause wide number of changes within a species.

The shuffling of genes during sexual reproduction also causes variations in species. Crossing over and independent assortment are the two phenomena which occur during meiosis and allow variations among organisms of the same species.

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.