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

Example Input: Passage: The most common mode of asexual reproduction is through the formation of asexual spores, which are produced by one parent only (through mitosis) and are genetically identical to that parent (Figure 24.8). Spores allow fungi to expand their distribution and colonize new environments. They may be released from the parent thallus either outside or within a special reproductive sac called a sporangium. Answer: spores
Example Output: The most common mode of asexual reproduction is through the formation of asexual these?

Example Input: Passage: The cell membrane is made up of a phospholipid bilayer, two layers of phospholipid molecules. Notice the polar head group of the phospholipid is attached to the phosphate, and the tails are two fatty acid chains. The head group and tails are attached by a glycerol backbone. Answer: cell membrane
Example Output: What basic cell structure is made up of a phospholipid bilayer and two layers of phospholipid molecules?

Example Input: Passage: The population growth rate is how quickly a population changes in size over time. The rate of growth of a population may be positive or negative. A positive growth rate means that the population is increasing in size because more people are being added than lost. A negative growth rate means that the population is decreasing in size because more people are being lost than added. Answer: population growth rate
Example Output:
How quickly a population changes in size over time is known as what?