Why did Darwin use the phrase “descent with modification” rather than “evolution”?

Ectocarpene is a volatile, sperm cell-attracting material released by the eggs of the seaweed ectocarpus siliculosus. its constitution is all the double bonds are cis, and the absolute configuration of the chirality center is s. draw a stereochemically accurate representation of ectocarpene.

When analyzing tree rings, what do scientists assume a thin ring indicates?

Which of the following is a period in the paleozoic era? devonian cambrian permian all of the above