The correct answer is option 1 - increases. Moving from the polar region towards the equator, the diversity of plant and animal species tends to increase. This is because the equatorial regions have a more stable and warmer climate, which provides favorable conditions for a wide range of plants and animals to flourish. The polar regions, on the other hand, have harsher and colder climates, limiting the number of species that can survive. Additionally, the equatorial regions have a greater variety of habitats such as rainforests, grasslands, and coral reefs, which further contribute to higher species diversity. Therefore, as one moves closer to the equator, the availability of resources and suitable environmental conditions increase, leading to an increase in the number and variety of plant and animal species.