Given a scientific passage and an answer, generate a question for the given answer.

[EX Q]: Passage: Air movement takes place in the troposphere. This is the lowest layer of the atmosphere. Air moves because of differences in heating. These differences create convection currents and winds ( Figure below ). Answer: troposphere
[EX A]: What is the lowest layer of the atmosphere called?

[EX Q]: Passage: In Chapter 2 "Molecules, Ions, and Chemical Formulas" and Chapter 5 "Energy Changes in Chemical Reactions", you were introduced to several structural units that chemists use to classify organic compounds and predict their reactivities. Thesefunctional groups, which determine the chemical reactivity of a molecule under a given set of conditions, can consist of a single atom (such as Cl) or a group of atoms (such as CO2H). The major families of organic compounds are characterized by their functional groups. Figure 24.1 "Major Classes of Organic Compounds" summarizes five families introduced in earlier chapters, gives examples of compounds that contain each functional group, and lists the suffix or prefix used in the systematic nomenclature of compounds that contain each functional group. Answer: their functional groups
[EX A]: How are the major families of organic compounds characterized?

[EX Q]: Passage: The gene theory is the idea that the characteristics of living organisms are controlled by genes, which are passed from parents to their offspring. A gene is a segment of DNA that has the instructions to encode a protein. Genes are located on larger structures, called chromosomes , that are found inside every cell. Chromosomes, in turn, contain large molecules known as DNA (deoxyribonucleic acid). Molecules of DNA are encoded with instructions that tell cells what to do. To see how this happens, click on the animation titled Journey into DNA at the following link: http://www. pbs. org/wgbh/nova/genome/dna. html . Answer: gene theory
[EX A]:
Which theory is the idea that the characteristics of living organisms are controlled by genes, which are passed from parents to their offspring?