Corridors and Population Dispersion
Part I. Introduction and Review of Relevant Biology
1. Energy transfer becomes inefficient in higher trophic levels in a food chain. Predators utilize more energy in obtaining food than their prey. The number of organisms and the amount of biomass defines energy relationships among organisms in trophic levels. Most top predators are huge in size but their population is lower because there is not enough energy to support a large population of these predators (Odum and Barrett).
2. A population of infinite size is seen less likely to evolve since it would be almost resistant to random fluctuations within the environment. Small populations on the other hand are prone to genetic drift or the random fluctuations of frequencies of alleles and genotypes. Genetic drift is influenced by bottleneck event such as natural hazards and hunting; and founder effect in which founding individuals are geographically isolated from the original population when forming a colony. Such phenomenon can be problematic to smaller populations because of the propensity to lose several generations which further leads to extinction (Schaeffer).
3. The concept that was used to describe the population size of breeding animals is known as effective population size. As what have been discussed, restriction of movement of jaguars limits their foraging range and their potential to find their mate for reproduction. These factors may decimate the number of breeding jaguars.
4. It is important to protect endangered species to ensure the balance in the food chain. That is, top predators like jaguars are very important in population control of species in the lower trophic level.
Part II. Nature Preserves and Corridors
1. The island biogeography theory suggests that the number of species found in an undisturbed island is influenced by immigration and extinction of species. With respect to natural park design, it is better to use a larger area than a series of small fragmented area of preserves. In case of preserves being linear, such connection with a corridor should be considered to allow large carnivores like jaguars to move freely.
2. Nature preserves are limited in number and size because it is difficult to delineate boundaries, management responsibilities and organizational structures within the area. Drafted laws about parks and preserves are sometimes in conflict with laws that promote the economic interests of a nation which involve exhausting natural resources.
3. The Central Park in New York is one of the many examples of a corridor that was established in the United States under the management of Wildlife Conservation Society.
Part III. Experimenting with Corridors
1. Animals can move either actively or passively from one place to another. In active dispersal, the animal moves accordingly through its own ability. In passive dispersal however, animals that cannot move on its own use dispersal units to help in reproduction and exploration of new habitats. Animals can disperse by way of flying or land travel. Dispersion is influenced by several factors to include food availability, crowding and fluctuations in the local environment which can affect dispersal behavior (Croteau).
2. Plants use dispersal units known as disseminules to facilitate reproduction and utility of new habitats. Disseminules use agents like wind, water and animals that are capable of active dispersal. Dispersion in plants can be a result of avoiding competition of resources, and as a response to environmental changes (Croteau).
3. Haddad showed in his study that pine forests are not barriers to butterfly movement. However, animals such as gopher frogs in the long-leaf pine forest are restricted in their movements. Long leaf pine dominant habitats also classified as heterogeneous habitats by Roznik et al. is a result of a fire maintained habitat having an open canopy. This type of habitat is preferred by a gopher frog as opposed to a homogenous pine habitat that restricts its movement (Roznik et al.).
4. Based on the patch size alone, it seems like Haddad intends to study the dispersal patterns of small volant and non-volant mammals and avifauna as well.
5. It seems obvious in the map that Haddad and his colleagues tries to compare the movement of a particular species of interest in an isolated patch and patches connected by corridors. Mean average of movements of species of interest through capture-recapture method can be gathered to compare the influence of corridor over species of interest. Movement data for isolated patches can be collected in patches 1, 4, 5, 10, 13, 14, 17 and 21. For connected patches, data can be collected from patches 2, 3, 6, 7, 8, 9, 11, 12, 15, 16, 18, 19, 20, 22, 23, 24, 25, 26 and 27.
Part IV. Method and Results of the Study
1. In general, higher proportions of movements of organisms were observed in connected patches ad opposed to isolated ones. Indeed, there is a positive corridor effect.
2. Species of butterflies such as Euptoieta claudia and Junonia coenia, a small mammal Peromyscus polionotus, and two species of plants having seeds dispersed by birds (Rhus copallina and Myrica cerifera) were noted to have been significantly influenced by corridors.
3. Different organisms have different adaptive strategies for survival. Butterflies move with ease as opposed to terrestrial dwelling animals like rodents because these insects can fly. Flying in contrast to other modes of migration is not heavily influenced by barriers. This also makes it easier for birds to disperse the seeds of the two aforementioned plant species.
4. (a) The word suggests in the statement means that Haddad and his colleagues are looking at the possibility that corridors may influence movements of organisms. "Do not demonstrate" means that they acknowledge the fact that there may be other factors that were not included in their data that could help them back their claim. To demonstrate lexically means there is a proof to back your claims. It is in this regard that the researchers were fair in the assessment of their study because their conclusions were limited to the scope of their study.
(b) The researchers suggested that their study requires more data on population variability and genetic diversity. Something that I will not dare contend because these factors are relevant to how species behave and adapt to the changes in their environment. This in turn, affects the population size. As was previously mentioned, genetic drift can lead to loss of generations in populations and even extinction of species. Thus, it is only relevant to know genetic variability.
(c) DNA samples could be taken to tag species and to know their genetic variability.
5. A border fence limits the movement of a jaguar to forage and reproduce. As Haddad et al. suggested corridors may play a significant role in the movement of species. Thus, the presence of a border fence may decimate the population of the jaguars because they become isolated.
Impact of Human Population
1. As human population expands, we expect a growth in the demand for food, water, and other basic necessities that would entail harnessing our natural resources. Statistics have shown that there's a rapid decline in forest cover due to an increase in urbanization rates. Water tables have been extensively extracted while coastlines remain under pressure. Pollution and environmental degradation has been rampant and has been linked to several emerging diseases.
2. Without the practice of sustainable development, population stabilization and resource conservation will not be achieved. Social inequality and the unequal distribution of capital compel people in the grassroot level to resort to unsustainable practices of harnessing resources. There also has to be a solid policy that would address the problems and issues of energy resources.
3. A program that encourages the public to save energy and their resources and to practice the concept of reducing, reusing and recycling waste materials could be beneficial towards achieving sustainable development. Information education campaign should be conducted to increase people's awareness on how population growth also impacts the degradation of our environment.
4. Slowing population growth rate means that we do not have to exhaust our natural resources to meet our demands for survival. A low population size means that it would be less difficult to compete for resources. For instance, people will have a better access to food and energy. People are also able to enjoy the benefits of a more quiet lifestyle since there would be less crowding. There would be an ample amount of clean water for the household and the rate of pollution becomes lower because the rate of urbanization decreases as well.
5. According to Malthus, super power nations would have to wage war against each other for the natural resources. Lack of potable water can lead to death and poor hygiene practices while scarcity of food can cause famine. More people become sick because communicable disease can be easily transferred from one person to another. Such imbalance will lead to the continuous degradation of the environment.
Works Cited
Croteau, E. K. "Causes and Consequences of Dispersal in Plants and Animals." Nature Education Knowledge, 3.10(2010): 12. Print.
Odum, E. P. and G.W. Barrett. Fundamentals of Ecology. Toronto, Canada: Thomson Brooks/Cole. 2005.
Roznik, E. A., S. A. Johnson, C. H. Greenberg and G. W. Tanner. "Terrestrial Movements and Habitat Use of Gopher Frogs in Long Leaf Pine Forrest: A Comparable Study of Juvenile and Adults." Forrest Ecology and Management, 2009. doi: 10.1016/j.foreco.2009.10.007. Web.
Schaeffer, S.W. (11 June 2009). Genetic Changes in Populations. Penn State Biology 110 Badic Concepts and Biodiversity. Atlassian Confluence 5.4.1, Team Collaborative Software. Web. 24 Jan. 2014. <https://wikispaces.psu.edu.display/110/Master/Genetic+Change+in+Populations.
