Because through natural selection, only the fittest survive. when the fittest come together and reproduce then the species continues and evolves with only the fittest and strongest genes.
The structure of DNA is called a double helix because DNA is made up of two strands of nucleotides wound together in a spiral.
DNA has two strands that run opposite of each other and twist together much like a twisted ladder. Each backbone of the ladder is made up of alternating groups of sugar and phosphate groups.
Answer:
carbohydrate + oxygen = carbon dioxide + water + energy
