Which of these is a characteristic of index fossils? (7 points) a Found in the topmost rock layer b Found in many layers of the same rock c Have already established relative age d Are limited to a particular geographic location

Sydney drew a flow chart to illustrate the nitrogen cycle. which labels best complete the flow chart? x: producers undergo photosynthesis. y: nitrogen compounds are released into the air. x: nitrogen compounds are released into the air. y: producers undergo photosynthesis. x: free nitrogen is in the atmosphere. y: producers absorb nitrogen compounds through their roots. x: producers absorb nitrogen compounds through their roots. y: free nitrogen is in the atmosphere.

Which of these is not a function of some membrane proteins ? a. allowing polar molecules to enter the cell b. recognizing other types of cells c. receiving messeges from other cells b. carrying messages to oher cells

Describe the function of the endomembrane system? what organelles are involved?