What was the selective pressure on the sea urchin population?​

Which codon is the code for the amino acid histidine (his)?

What are the three different shapes, or structures, of carbon-based molecules

The table below shows the elements that mainly comprise each of the four layers of earth: elements in layers layer main elements crust oxygen, silicon mantle iron, magnesium outer core iron, nickel inner core iron which of these elements make up the layer that is 0.2 to 1.1 percent of earth's total diameter?