Biologists typically use the style recommended by the Council of Science Editors (CSE) to format their paper, to cite sources in the text of the paper, and to list the sources at the end. The CSE describes three citation systems in Scientific Style and Format: The CSE Manual for Authors, Editors, and Publishers, 7th ed. (Reston: CSE, 2006).
In the name-year system, the author’s last name and the date of publication are cited in the text.
In the citation-sequence system, each source is assigned a number the first time it is used in the text, and the same number identifies the source each time it appears.
In the citation-name system, each source is assigned a number in the order in which it appears in the alphabetical list at the end of the paper. That number is used each time the source is cited in the text.
With all three systems, biologists place bibliographic information for each source at the end of the paper in a section called References or Cited References.
For more on CSE style:
CSE Documentation