Chargaff wrote: "DNA is in its composition characteristic of the species from which it is derived. This can ... be demonstrated by determining the ratios in which the individual purines and pyrimidines occur
There appear to exist two main groups of DNA, namely the 'A-T type,' in which adenine and thymine
predominate, and the 'G-C type,' in which guanine and cytosine are the major constituents."
1. What does this mean? Put Chargaff's ideas above into your own words.

this protocol provides a detailed procedure for agarose-based ip to purify and enrich the protein of interest.

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the oldest known insects are believed to live around 400 millions ago as suggested by the fossil records.   some plants having woody stems also evolved during this time.

after the evolution of insects the first four legged species or the tetrapods evolved in shallow freshwater habitats from the intermediate species approximately 397 million years ago. the tetrapods went on conquering the land giving rise to amphibians, reptiles, mammals and birds.

the major split in tetrapods first occurred 340 million years ago branching off from amphibians.

363 million years ago when the carboniferous period began the insects started roaming on land and taking flights, following which the four limbed tetrapods adapted in the terrestrial habitat.