Fossil evidence indicates that the following events occurred in what sequence, from earliest to most recent?

1. Protostomes invade terrestrial environments.

2. Cambrian explosion occurs.

3. Deuterostomes invade terrestrial environments.

4. Vertebrates become top predators in the seas.

#Question id: 46

#Section 2: General Biology

The three-dimensional structure of a protein is determined primarily by:

#Question id: 5250

#Section 3: Genetics, Cellular and Molecular Biology

A researcher would like to map the location of galE and trpA genes in a new species of bacterium that appears to be closely related to E. coli. He decides to use cotransduction, and generatesnappropriate donor and recipient strains. He is disappointed when cotransduction is not seen in his experiement. What is the most reasonable explanation for this situation?

#Question id: 62

#Section 2: General Biology

We can represent atoms by listing the number of protons, neutrons, and electrons—for example, 2p+, 2n0, 2e- for helium. Which of the following represents the 18O isotope of oxygen?

#Question id: 2297

#Section 3: Genetics, Cellular and Molecular Biology

Which structure is composed of phospholipids and regulates the movement of substances in and out of cells?

#Question id: 3950

#Section 3: Genetics, Cellular and Molecular Biology

Which of the following in not true of the nuclear envelope?