AQA Biology Unit 5 Synoptic Essay Help!

I've just been assigned an essay title and I really have no idea where to start, or what to write about.

The title is, 'Ways in which different species of organisms differ from each other'

Any help would be greatly appreciated

Choose a number of topics, for example you could talk about how their digestive systems differ, their gaseous exchange systems, surface to volume ratio, Diets, roles in ecosystems... The essay titles given are always very broad but the examiner isn't looking for specific areas most of the time, just relevant and correct information

i thought that essay wud be about speciation.

A good approach to synoptic essays is to make a list of headings of topic areas first. For example: Genetic differences, methods of nutrition, warm/cold blooded, gas exchange methods, role within particular cycles, etc. Then fill in for different species. There you have the bare bones of your essay waiting to be fleshed out.

You can apply that method to pretty much any synoptic topic.