From 900 to 1200 words.
Introduction:
•    Briefly describe the problem/issue and list the scientific ideas or processes which address the problem/issue.

•    In this essay I will consider advantages and limitations of (the scientific ideas or processes) with regard to (social/economic/political/environmental/cultural/ethical) factors.
•    In this essay I will argue that (insert thesis statement here).

Body: First discuss all the limitations, then all the benefits

Conclusion:
•    Very briefly summarise the main ideas of the essay and the main issue.
•    End with a recommendation based on your argument