Relative dating best helps determine fossil age. It's where layers of sedimentary rock and fossils pile up on top of each other; the oldest fossils being in the bottom layer and the youngest in the top.
Eukaryotic cells do not have a nucleus. The nucleus is where DNA, your genetic material, is usually stored. Prokaryotic cells do not have a nucleus. The DNA just floats around the cell instead of staying in one designated area.
Natural selection can cause speciation, which increases the biodiversity of an ecosystem. Several bacterial colonies are placed on a petri dish that contains agar with antibiotics. After 24 hours, ninety percent of the original bacteria die, but the remaining ten percent survive and later reproduce.