The most plausible hypothesis to explain why species richness is higher in tropical than in temperate regions is that
a. Tropical communities are younger.
b. Tropical regions generally have more available water and higher levels of solar radiation.
c. Higher temperatures cause more rapid speciation.
d. Diversity increases as evapotranspiration decreases.

Verified step by step guidance

1. Understand the concept of species richness, which refers to the number of different species represented in an ecological community, landscape, or region.
2. Consider the environmental factors that can influence species richness, such as climate, availability of resources, and ecological interactions.
3. Evaluate the hypothesis that tropical regions generally have more available water and higher levels of solar radiation, which can support a greater diversity of life forms. This is because these conditions can enhance primary productivity, providing more energy and resources for a variety of species.
4. Analyze the role of temperature in speciation. Higher temperatures in tropical regions can lead to faster metabolic rates and potentially more rapid evolutionary changes, contributing to increased speciation.
5. Examine the concept of evapotranspiration, which is the sum of evaporation and plant transpiration. Consider how changes in evapotranspiration might affect species diversity, noting that higher evapotranspiration rates are typically associated with more productive ecosystems.

Key Concepts

Species Richness

Species richness refers to the number of different species represented in an ecological community, landscape, or region. It is a measure of biodiversity and is often used to compare different ecosystems or geographic areas. Higher species richness indicates a greater variety of species, which can contribute to ecosystem stability and resilience.

Tropical vs. Temperate Regions

Tropical regions are characterized by warm temperatures and high levels of solar radiation and precipitation, leading to lush vegetation and diverse ecosystems. In contrast, temperate regions experience more seasonal variations in temperature and precipitation, which can limit the diversity of species. These environmental differences are key factors in explaining variations in species richness between these regions.

Evapotranspiration

Evapotranspiration is the process by which water is transferred from the land to the atmosphere by evaporation from soil and other surfaces and by transpiration from plants. It is influenced by temperature, humidity, and solar radiation. In ecological studies, higher evapotranspiration rates are often associated with increased plant growth and productivity, which can support greater species diversity.