Population Biology Is an Important Aspect of Evolutionary Biology
Population biology refers to the study of populations of organisms. The study narrows down and specializes to the regulation of population size, life history traits, and extinction. Many people confuse this term with population ecology since we frequently witness the scholars use the two aspects interchangeably. This paper therefore hypothesize that population biology is an important aspect of evolutionary biology.
While population ecology merely deals with plants and animals, population biology is more specific since it deals with the study of diseases, microbes, and viruses. Rather than merely studying plants and animals as in ecology, it is very important to determine the factors that influence them. Diseases, viruses and microbes are global issues in terms of their effect on the living things, hence the importance of population biology. However, the interchangeable use of the two is still applicable since they relate. By studying population biology, we are likely to understand organisms deeply (Provine, 1988, pp. 49–79).
Population of organisms is always changing due to quite a number of factors, which affect them. The scholars in the field of biology have considered this to understand these effects. The understanding of this may involve the relationship between the organisms and the effects, the level of the effects and the appropriate control measures. We feel the importance of population biology since it focuses on the biological processes affecting the organism population. It is only through the study of this organism in population biology that we access all the relevant pieces of information regarding the frequent change, specifically decline, in population of organisms. Population biology as a sub-discipline therefore plays a vital role in the life of plants and animals (Warwick et al, 2009, pp. 194 – 196).
The relevance of population biology is obvious in plant pathology because it is always a population of parasites that cause plant diseases. A single pathogen lesion on one single leaf does not cause a significant economic on the well-being of the ecological balance. This is so because the effect that results is rather negligible and therefore we will not witness any alteration in the ecology (Warwicket et al, 2009, pp. 194 – 196). However, an epidemic that involves a large number of parasites and their host plants cause a very serious epidemic that may be out of hand. This implies that the significance emerges beyond a negligible case; it must be a question of millions of parasites and hosts rather than one parasite and one host . Parasite attack normally causes plant diseases under most conditions and the subsequent need to control the diseases is an important issue. We expect the plant pathologist in question to develop proper methods of controlling the whole pathogen population to enable him or her control the disease that is likely to result or that already exists. It is therefore very important for everybody and more so pathologists to understand the population biology of plant pathogens to design appropriate strategies to enable a successful control.
The organisms living and thriving in a given geographical region normally exhibit reproductive continuity. The inheritance of this continuity is evident from one generation to another. We usually identify these organisms in a population, which implies to a group of organisms originating from the same species and occupy the same geographic region in addition to exhibiting reproductive continuity from generation to generation. It is a common knowledge that we frequently witness ecological and reproductive interactions taking place among members of the same population when we compare the case to members from different populations. We may or not decide to consider deeply the assumption to find the truth. We still have sufficient information that population biology is very important since all these issues revolve around the population of organisms (Wiens, 2004, pp.914–923).
It is quite important to understand how diseases progress, how the pathogen population multiplies through time and how the pathogen population move through space. Furthermore, the understanding of distribution and determinants of frequency of diseases in plant populations is also a factor to consider. Actually, these issues are under study in the field of biology. Epidemiology and population genetics, sub-branches of population biology, consecutively, covers these particular issues. The application of this sub-discipline of evolutionary biology is very wide having extended to this field hence very important (Provine, 1988, pp. 49–79).
Natural selection and mating systems are important issues that are major factors in population features since they contribute directly towards them through reproduction. These are among the factors that lead to the genetic change, or evolution, in populations with changing time and space. We cover this under population genetics, which is a sub-branch of population biology (Warwick et al, 2009, pp. 194 – 196).
Epidemics are an issue affecting the behavior and existence of the organisms in the ecological systems thus works towards continuously altering the ecological balance. The effects of epidemics count to issues that emerge a global concern. We realize that epidemics results from the activities of other infectious or rather destructive organisms. It is then with concern that the scholars study epidemiology and establishes a sound relationship between it and population genetics. Considering this, we realize that there exist sizeable overlaps between the two sub-branches of population biology. The two have many features in common which constitutes a kind of similarity between them. Figure 1 highlights the similarities. FIGURE1.
Similarities between Epidemiology and Population Genetics
Dispersal distance of pathogen propagules
Measures initial inoculums load
Measures genotype flow
Determines the disease progressive curve shape
Functions as a fitness parameter
Size of pathogen population
Determines the measure of disease incidence
Affects the degree of generic drift
Summary of the table 1
Epidemiology and population genetics use the dispersal to measure inoculums load and genotype flow respectively.
Latent heat influences both measure of disease incidence and fitness parameter in the respective.
Size of pathogen population determines the measure of disease incidence and degree of the genetic drift in the two respectively (Provine, 1988, pp. 49–79)…
Agriculture as a science strives to fit in the ecosystem, for which reason a concept of an agro-ecosystems emerges which tend to study the relationship between the two. In this concept, we major on how a control method affects the population genetics, or evolution, of the pathogen population in question. The methods may include introducing a resistance gene, application of fungicide, imposition of a quarantine or practicing crop rotation. All these measures apply just to target a population of pathogens rather than a single one hence population biology still applies (Wiens,2004, pp. 914–923).
Closely related to population biology, scholars study population genetics, in which we generally consider five evolutionary forces. These are forces, which influence the pathogen populations and they include mutation, genetic drift, reproduction, and mating system, gene flow, and natural selection. All these forces contribute to an alteration in the status of population in one way or the other. Therefore, for population to exist in the normal way we expect these forces to be present, otherwise Hardy-Weinberg equilibrium will emerge as a feature in the population. We can easily calculate the allelic frequencies of organisms using The Hardy-Weinberg model. The table2 below shows the counts of the number of individuals with a given genotype for six variable (polymorphic) two-allele loci recorded in California and Alaska (Warwick, et al,.2008. p. 731).
Table2. Counts of number of individuals with a given genotype for six variable (polymorphic) two-allele
We can use this table find the allelic frequency of the EST locus in California population.
(Take n=64), S=37 so SS =74 S alleles, 20 (SF) heterozygous implies 20 S alleles and 20 F alleles; 14 FF genotype implies 14 F alleles. Therefore, implies 94 S alleles and 34 F alleles.
Either F/Total number of alleles or S/ Total number of alleles gives the frequency.
Frequency of S alleles =94/128= 0.734
Frequency of F alleles= 34/128= 0.266
All these great studies are under population biology. We realize that population biology focuses deeply on the biological processes that affect populations of organisms. Considering its applications in various fields, Population biology is quite relevant to plant pathology and all the other biological aspects that revolve around population. We consider two biological factors in question in terms of population rather individual organisms. Therefore, the population biology is an important aspect of evolutionary biology.
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Wiens J, (2004). “What is speciation and how should we study it?”. American Naturalist 163 (6): 914–923
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