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

[Q]: Passage: Many samples have a lot of variation in measurements. Variation can be described with a statistic called the range. The range is the total spread of values in a sample. It is calculated by subtracting the smallest value from the largest value. Answer: range
[A]: What term is used to describe the total spread of values in a sample?

[Q]: Passage: Colonial organisms were probably one of the first evolutionary steps towards multicellular organisms. Algae of the genus Volvox are an example of the bridge between colonial organisms and multicellular organisms. Each Volvox , shown in Figure above , is a colonial organism. It is made of up to 50,000 photosynthetic flagellate algae that are grouped together into a hollow sphere. Volvox live in a variety of freshwater habitats, and were first reported by Antonie van Leeuwenhoek in 1700. Answer: multicellular
[A]: Colonial organisms were probably one of the first evolutionary steps towards which type of organisms?

[Q]: Passage: Predators play an important role in an ecosystem. For example, if they did not exist, then a single species could become dominant over others. Grazers on a grassland keep grass from growing out of control. Predators can be keystone species . These are species that can have a large effect on the balance of organisms in an ecosystem. For example, if all of the wolves are removed from a population, then the population of deer or rabbits may increase. If there are too many deer, then they may decrease the amount of plants or grasses in the ecosystem. Decreased levels of producers may then have a detrimental effect on the whole ecosystem. In this example, the wolves would be a keystone species. Answer: keystone
[A]:
What type of species have a large effect on the balance of organisms in an ecosystem?