It's worth pointing out that one of the very basic essay question titles can come out. Like.....
'Write about the different types of cells in organisms'
If I got that in the exam without revising it, I would facepalm myself hard.....
So learn some cells in a good amount of detail.
Remember that for any essay, each small topic should only be a maximum of 10 lines as you will only gain 2 marks for scientific content. So your looking for 6-8 good points to talk about, if your looking to score around 20+/25 marks for the essay...... Background knowledge outside of the syllabus will help.
Like for example if one of your paragraphs are about enzymes, you could bring in a fact or something, that is outside of the syllabus (e.g. the human body contains roughly 50,000 different enzymes) which will impress your examiner.
xD