Question

From an ecological perspective, either explain or define the following:

1) Lotka and Volterra model and four outcomes of competition between two species

2) Tilman’s model

3) Gause’s hypothesis

4) r-selection and K-selection theory

5) Grime’s theory of plant strategy

Answer 1

Lotka-Volterra model:

• It compares the population dynamics of species as predator-prey model. It also describes the relation between intraspecific competition (competition among the population of same species) and interspecific competition (competition among the population of different species).
• It thus concludes, that co-existence between two species is possible, if intraspecific competition is greater that interspecific competition.
• It considers the various levels of resources, or different types of resources, and the ability of the species to use these resources.
• The assumptions are based on logistic -competition model, based on logistic growth equation.
• dN/dt = rm N (1 - N/K)

Tilman’s R* competition models:

• R* was described by Tilman’s model as: The amount of resource at which, the birth rate of a species equals the mortality rate of the species. Thus, at R*, the species can maintain a stable and equilibrium population size.
• Thus, the R* rule was predicted as: When several species are competing for a single “limiting nutrient” or resource, the species that have lowest value of R*, will competitively displace other species, regardless of the initial conditions (like population size of a species).
• Thus, Tilman’s model considers, the rate of resource consumption of each species and does not explicitly considers change in resources.
• The assumptions are related to relative positions of the zero net growth isoclines, describing the zero net growth of populations at a certain level of limiting resource.