instruction:
Given a scientific passage and an answer, generate a question for the given answer.
question:
Passage: Cells are the tiny building blocks of living things. They couldn't be discovered until the microscope was invented. The discovery of cells led to the cell theory. This is one of the most important theories in life science. Answer: cells
answer:
What are all living things made of?

question:
Passage: Population density is the average number of individuals in a population per unit of area or volume. For example, a population of 100 insects that live in an area of 100 square meters has a density of 1 insect per square meter. If the same population lives in an area of only 1 square meter, what is its density? Which population is more crowded? How might crowding affect the health of a population?. Answer: population density
answer:
What is the term for the average number of individuals in a population per unit of area or volume?

question:
Passage: This scene is from Anza-Borrago California Desert Park. However, deserts exist around the globe. You might find a similar picture of a desert in Africa. The desert is one type of biome. Answer: biome
answer:
A desert is a type of what community in an ecosystem?