Final answer:
Austrian biochemist Erwin Chargaff discovered that in DNA, adenine equals thymine and guanine equals cytosine, a finding known as Chargaff's rules.
Step-by-step explanation:
The scientist who discovered that in DNA from any species, the amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine was Austrian biochemist Erwin Chargaff. Chargaff's examination of DNA across various species led to this pivotal finding, known as Chargaff's rules. These rules indicate that A = T and G = C, implying that the bases pair up in a consistent and predictable manner, which was instrumental in the development of the DNA double helix model by Watson and Crick. This discovery is known as Chargaff's rules. It was a crucial finding that played a significant role in the development of the DNA double helix model proposed by Watson and Crick.