Which statement accurately describes the rock layers?
Layer 8 is older than layer 1.
Layer 3 is younger than layer 6.
Layer 4 and layer 10 are the same relative age.
Layer 2 and layer 9 are the same relative age.

in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".