Terrestrial ecosystems (tetrapods)
DNA is a chain of nucleotides bonded together. On that chain there are particular portions of it that the sequence of the nucleotide codes for particular proteins; this is known as a gene. In eukaryotric cells, DNA is coiled around proteins such as histones to form chromatids which when two join at the centre by a centromere to form a chromosome.
Temperature difference and Earth's tilt
Producers are where the cellular respiration occur in the biosphere.
