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What type of organism has a population size that can dramatically fluctuate with environmental conditions?

  1. Keystone species

  2. Pest species

  3. Pioneer species

  4. K-selected species

The correct answer is: Pioneer species

Pioneer species are the first organisms to colonize a barren or disturbed area, such as after a natural disaster or on newly formed land. They are able to quickly establish and reproduce, leading to potentially large population sizes. This makes them resilient to changes in environmental conditions, as they can quickly recover and recolonize after disruptions. Keystone species and K-selected species do not typically experience dramatic fluctuations in population size, as they have evolved strategies to maintain a stable population. Pest species, while they may have large population sizes, are often introduced by humans and are not naturally occurring in the environment. This can make them less resilient to drastic changes in the environment.