I haven't done any modules, but I can't imagine the answer changes depending on scientific discipline.

The lines are nectar guides.

The theory is that bees see the UV spectrum, so see flowers differently from us. The lines show up more clearly to bees, and presumably other pollinating insects, and guide them towards the nectary.

Some pictures showing 'normal', UV and IR flowers on this site http://www.naturfotograf.com/UV_flowers_list.html

Is this any use to you? http://blog.mbbka.org.uk/category/ed...bbka-module-6/