Food webs question- prairie animals and plants

Hello!

In Bio lab, we were creating food webs. Unfortunately, one of them I just can't figure out even though it seems to be easy. These are the prairie animals and plants. We were supposed to organize them into a food web.

grass, daisies, sunflowers, lupines, ticks, grasshopers, butterflies, bees, rats, coyotes, hawks, badgers, fungal and bacterial species.

Can someone please help me with that?

Also, a fairly easy question: why do scientist estimate population size? This is a question that will also appear on the final lab practical I have this coming Thursday.

Thank you!!!!