Energy Flux in Ecological Systems
Take Home Exam
Feb 15, 2014
The concept of ecology considers interactions between organisms and their environment across several scales of analysis. Population ecology includes investigations of the physiological principles that modulate how individuals interact with their environment, and resource competition theory that explores the dynamics of both individual and interacting species. Community ecology focuses on large assemblages of species and considers how in fluxes of matter and energy can define collections of species within an ecosystem. Consequently, the concept of an ecosystem must consider how nutrient cycles shape the rate and efficiency of energy transfer among and between species and communities. This essay will attempt to highlight the key role of energy transfer across varying levels of complexity in ecology.
There are four essential elements (carbon, hydrogen, oxygen, and nitrogen) required by all living matter. The proportions of nucleic acids, lipids, proteins, and carbohydrates will be regulated in all living things in some manner, although individual species will differ in the chemistry and regulation of their chemical content. The study of the patterns and processes associated with the chemical content of species is known as ecological stoichiometry, and it plays a fundamental role in ecology. Most plants require nutrients in relatively set proportions to grow, defined by the Redfield ratio of carbon:nitrogen:phosphorus at 40:7:1, respectively. Based on this ecological stoichiometry, as well as species-specific regulation of nutrient ratios, many predictions can be made about how species interact.
There are many predictions of resource competition that can be made when multiple co-occurring individuals utilize the same limiting resources. Leibig's Law of the minimum states that the abundance of an organism will be relative to the most limiting resource in it's environment, and this law has been extended to consider resource dynamics in communities through Tilman's resource competition theory.
Intra- and interspecific competition
Negative feedback processes can occur when different individuals within a population compete for a limiting resource. This is termed intraspecific competition. These effects can be extended to include pairwise interactions between species (e.g. competition, mutualism, predator-prey), which is termed interspecific competition. To illustrate this concept and how it relates to resource limitations, the concept of predator-prey interactions will be discussed briefly.
Gause conducted early experiments on simple species such as yeast and paramecia to examine simple species assemblages and determine theoretical conditions of resource abundance that might allow species to stably coexist (Gause 1934). His experiments were coupled with the mathematical framework of Lotka-Volterra equations...