Tufts OpenCourseware
Author: Colin Orians

1. Discussion Questions

1.1. Chapter 5: Tropical Biota

  • Density dependence vs. density independence. They argue that biological populations in the tropics are regulated by biotic factors than temperate populations whereas abiotic factors are more important in temperate areas. Why?
  • Why are pest and disease problems greater in the tropics than in the temperate areas?
  • How do plants defend themselves against herbivores? Discuss resistance (chemical), avoidance (time or space), and tolerance traits.
  • If we assume that biotic interactions are more intense in the tropics, what are the evolutionary consequences of this?
  • What are examples of adaptations among plants and animals in tropics that have not been able to evolve in the temperate areas?
  • What is meant by regional and local species diversity? Why are neotropical forests especially plant species-rich? Think about geological age, environmental stress (e.g., soil nutrient availability), spatial variation in environmental conditions.
  • Which trends in species diversity are found when comparing different tropical ecosystems? Mangroves, savannas, rainforests
  • Review the different hypotheses about the increase in species diversity from the Arctic and Antarctic to the equator. 1) more speciation (faster evolution) and less extinction (low rates of extinction) – area and time-dependent, 2) intermediate disturbance hypothesis, 3) stochasticity, 4) more niches. How would you differentiate among them?