What are some reasons that parasites have not previously been incorporated into food webs?

Fossils can only be formed when? if mud, silt or tar is in the area to preserve the fossil ierosion does not occur and allows the fossil to form oxygen and microorganisms cannot decay the bones the area is dry and does not contain mud or silt

As a small change in a person's dna can cause a genetic disorder

What does the positioning of transcription factors determine?