Fossils are remains of organisms found in sedimentary rock. these remains are found in thousands of rock layers around the world and provide evidence for earth's long history of changing lifeforms. rock layers that formed more recently a. contain fossils of animals only. b. contain fossils of plants only. c. contain fossils that resemble existing species less closely than do fossils found in older rock layers. d. contain fossils that resemble existing species more closely than do fossils found in older rock layers.