Quiz 16 :
Species Abundance and Diversity
The communities and population are important parts of an ecosystem. The basic differences between community and population are as follows: Some of the distinguishing properties of a community are as follows: • Structure : The structure of a community is determined by the number of species, their relative abundance, and the diversity of species in it. • Interactions : The members of a community may interact to have potential out puts. The interactions are as follows: 1. Mutualism 2. Commensalism 3. Competition 4. Predation 5. Parasitism • Factors affecting community : The factors that influence the structure and composition of a community are abiotic and biotic factors of an environment. The abiotic factors may be temperature, humidity, air, pH etc. The biotic factors may include the members of the community and environment. A guild can be defined as a group of organisms that make their living in a common way. The study of guilds helps the ecologist to have a clear view of the animals in a community. Some examples of guild are as follows: • Insects in a community that feed on flowers. • Insects in area that feed on seeds. • Animals in an area that feed on herbs. A plant life form is a term assigned to a combination of the structure and growth dynamics assigned to any plant. Plant life forms enable the ecologist to get a better view of the plants in any community. Some examples of life forms are as follows: • Trees • Grasses • Annual plants
There is a wide variety of living beings present in any community. Many such communities combine to form the ecosystems that comprise of the nature on earth. This proves that in order to sample the species present in any substantial habitat on earth, the ecologists would have to take a list of the variety and number of each organism. This may include very small organisms like fungi to largest like whales or elephants. The major requirements for such an exercise may be: • Expertise man power. • Millions of scientist hours to perform the study. • Standardized sampling methodologies. • Extensive efforts in sampling. • Provision to conduct study of wide range from underground soil to tree canopies. All these requirements may be increased as per the increase in species number in any area. Hence, it becomes impossible to give a complete list of species that must comprise of all types of organisms in any substantial area on earth. It has been practically impossible to make such a precise listing. Hence, a complete list of species has not been determined of a substantial habitat anywhere on earth.
A lognormal graph shows a relative abundance of species in any area. In order to construct a lognormal graph, let us consider a hypothetical sample of any area. The population consist of ants in a given area. The observations are as follows: • Number of species of ants observed: 208 • Number of individuals studied: 4,058 On base of the above sampling, a typical lognormal distribution can be constructed as follows: The x axis is labelled as the number of individuals and y axis is labelled as number of species. The graph has a bell shape that is characteristic feature of a "typical" lognormal distribution. It can be also seen that the moderately abundant ants were of 30 different species (approximately). It also denotes some species were very high and some were very low in abundance.