Which of the following is NOT a characteristic of pioneer species? a. They are the first to colonize a new habitat. b. They are typically small and fast-reproducing. c. They require rich soil conditions to thrive. d. They help improve the habitat for other species.

To determine which option is NOT a characteristic of pioneer species, let's analyze each statement: a. **They are the first to colonize a new habitat.** - This is true. Pioneer species are known for being the first organisms to establish themselves in a previously uninhabited area. b. **They are typically small and fast-reproducing.** - This is generally true. Many pioneer species, such as certain grasses and lichens, are small and have rapid reproduction rates, allowing them to quickly populate an area. c. **They require rich soil conditions to thrive.** - This is NOT true. Pioneer species often thrive in harsh conditions, including poor soil. They are usually the first to grow in barren environments, where soil may be lacking in nutrients. d. **They help improve the habitat for other species.** - This is true. Pioneer species can help create conditions that allow other species to thrive, such as by adding organic matter to the soil or stabilizing the environment. Based on this analysis, the correct answer is: **c. They require rich soil conditions to thrive.**