Concepts in Ecology and Evolution
10 – Discuss the points for and against the use of the focus of neutral models to assess the effects of competition on community composition.
Points for:
– The neutral theory considers that individuals in a community are sympatric trophic and similar potentially competing for the same or similar resources (Hubbell 2001). The fundamental question the theory is the ecological equivalence of species in the community.
Points against:
– The initial assumption is that the neutral theory should be applied to relatively small spatial scales (Maurer & McGill 2004).
4) Make the distinction between determination and regulation of population abundance
The setting is the tendency of a decrease in population size when it is above a certain level, but increase in size when it is below this nível.A regulation of a population can only hasten the result of one or more dependent processes density acting on birth rates and / or mortality and / or movement.
Since the exact abundance of individuals is determined by the combined effects of all factors and all proceedings affecting a population, they are dependent or independent of density. The determination of abundance we understand how a specific population displays a particular abundance in a specific time and not some other abundance.
05) What does it mean metapopulation and how it differs from a simple population?
A metapopulation includes a collection of subpopulations, each of which has a real chance of extinction. It differs from a single population, because the processes of colonization, extinction and movement between subpopulations have more focus. Unlike a single population that is admitted as more or less homogeneous whose focus is given to the processes of birth, mortality and movement in a single population.
7) What are the factors responsible for changes in species composition during succession in an abandoned field?
A: Changes in species composition during the process of succession in an abandoned field are given by felled trees or death herbal countryside, with the creation of gaps in which begins a new series, following the pattern of dynamics in patches of many communities . Usually the beginning of plant succession occurs at due to the fact that these organizations provide the starting point of the food web and determine the very physical environment in which the animal is inserted, however, animals can dominate a series, affecting plant development by through heavy grazing or trampling.
9) What is meant by control from the bottom up and top-down control? What is the importance of each one as the ability to vary with the number of trophic levels in a community?
A: Control * above = situations where structure (abundance, species number) of lower trophic levels of consumers depends on the effects of higher trophic levels.
* Control from below = dependence on community structure such factors as concentration of nutrients, prey availability, that influence a trophic level from below.
The interaction between the controls causes the number of trophic levels vary, for example, in a four-level system, primary and carnivorous plants are restricted from above by predation, while the secondary herbivores and carnivores are limited to low up for competition.
10 – Discuss what is meant by the relationship between complexity and stability of food webs
Some time ago it was believed that the complexity led to population stability. From studies mathematical models of webs began taking into account the number of species, the connectivity of the web and the strength of interaction between species and concluded that the increase in the number of species increases the connectivity and strength of interactions average between species, which in turn reduces the tendency of the community return to its original configuration after suffering the disorder. Thus, the complexity leads to instability, not stability as it was believed. Thus, communities with higher species richness only become stable by reducing their average connectivity.
1. What do you consider to be the most important difference between natural selection and evolution?
Natural selection and evolution are complementary processes, and that natural selection leads to evolution, and evolution does not happen without there being some natural selection. The performance of each one alone would be impractical, so we can not point out differences between the two processes.
7. How the results of natural selection by parasites and predators differ from selection by the physical environment?
The selection made by the physical conditions of the environment do not interact with the organisms, ie certain condition changes and the body must adapt to this condition, however, the condition will not change in response to the organism. For example, if an extreme drought, the organisms have to adapt to survive the drought, but drought continues. Since natural selection that occurs with parasites and their hosts and with predators and prey, provides a co-evolution, ie acts as a selective force on another. For example, a host evolves to become more resistant to their parasites, concomitantly, the parasite evolves to become more virulent.
9. What is the difference between parallel and convergent evolution?
Parallel evolution: when people have time alone, but having the common ancestor, they follow similar patterns of diversification;
Convergent evolution: populations evolving from different ancestors, converge to very similar shapes and behaviors.