Question

scientists record the types of fossils found in different layers of sedimentary rock in one location. they observe that lower layers have more species than upper layers. which piece of evidence would help scientists understand the change in species numbers? environmental conditions at the time of deposition rate of sediment deposition presence of cross - cutting volcanic intrusions type of parent rock where the sediment weathered

Explanation:

To understand the change in species numbers across sedimentary rock layers, we need evidence related to factors that affect species survival and evolution. Environmental conditions (like climate, habitat, resources) at the time of deposition influence which species can thrive. The rate of sediment deposition (option 2) affects layer thickness, not species numbers. Cross - cutting volcanic intrusions (option 3) relate to rock formation timing, not species. The type of parent rock (option 4) affects sediment composition, not species numbers. So environmental conditions at deposition are key.

Answer:

A. environmental conditions at the time of deposition