Question

Ecology:

Be able to draw and describe in words the three hypothesized models of how species richness affects ecosystem function. Also be able to draw and label the H0, null hypothesis model. Be able to give examples of ecosystem function.

Answer 1

Species Richness (s) is a relative term that refers to the number of species in a community, and is directly associated with measuring the diversity of species in a given area.

Ecosystem Functions

Three levels of organisms regulate the flow of energy in ecosystems: the producers, the consumers, and the decomposers.

There are several hypotheses that have been proposed to explain species diversity patterns. Many of these hypotheses are based upon the idea that species are more diverse near the equator than near the poles. In other words, there is a recognized latitudinal gradient of species diversity on Earth.

There are three commonly recognized biotic species diversity hypotheses. They include: (1) The Heterogeneity Hypothesis, (2) The Competition Hypothesis, and (3) The Predation Hypothesis.

The Heterogeneity Hypothesis suggests that the more spatially diverse the community is, the greater the species richness.

The Competition Hypothesis introduces the concept of r and k selection. r-selected organisms are described as rapid growing organisms that have broad resource requirements and k-selected organisms are described as slow growing organisms that have narrow resource requirements.

The Predation Hypothesis says that predation opens up niches and reduces prey. Fewer prey lead to liberated resources which, if used by other species, leads to an increase in species richness. The concept of a keystone species is important to this theory. The keystone species is the species that a community is dependent upon and is often a predator. The keystone species maintains stability of the community which will increase species richness.