Problem Set, Research Paper Example

Problem #1. No Bats in the Belfry: The Origin of White- Nose Syndrome in Little Brown Bats by Dechaine JM and Johnson JE. Central Washington University, Ellensburg, WA National Center for Case Study Teaching in Science (NCCSTS).

In the winter months of 2006-2007, colonies of hibernating bats were affected with a disease known as “white-nose syndrome” (WNS), which decreased the population over 80% in areas surveyed.  Since the first observed outbreak, white-nose syndrome has been found over 1,200 miles from the original observed location.  In addition, studies have found that the disease has infected bats in 26 of the states within the United States, as well as four Canadian provinces.  (USGS,   )  It has been determined that White-nose syndrome is an infectious disease caused by a cutaneous infection of the fungus Geomyces destructans (Gd).  It has been previously hypothesized that the affected bats leave hibernation too early depleting fat stores, which are vital to survival in winter months.  In addition, the infectious fungus was observed in European bats; however, the populations were affected at low levels.  This observation suggests that the fungus is native to both North America and Europe, with possible genetic mutation or environmental change in the fungus.  The current paper discusses two testable hypotheses that could determine the link between the fungus and mortality rates.  (Warneke et al., IN PRESS)

In order to develop a testable hypothesis, the life history and habitat of the brown bat (Myotis lucifugus) was examined.  The life history of the brown bat has shown increased levels of survival with low population growths.  For instance, this species of brown bat has been recorded living 5-15 years or more with one offspring per year.  This species of bat rely on insects for food and during the winter months, insects disappear; therefore, the species has adapted a strategy to increase fat reserves during the fall and then hibernate during the cold winter months.  In addition, the bat lowers its body temperature to reduce metabolism and limit fat use.  Any arousal during hibernation can result in depletion of the fat reserves; therefore, repetitive arousal during hibernation can result in death due to the lack of fat reserves and food during the winter.  This life history analysis indicates that brown bat populations do not normally fluctuate under normal conditions; therefore, it can be predicted that changes to the physical environment or physiological changes to the bat can result in changes to normal population conditions.

In order to find out the cause for high mortality rates in bats with white-nose syndrome (WNS), investigation into the loss of fat reserves should be analyzed.  Hibernating bats physiologically have a lowered and controlled body temperature and metabolic rate.  It has been illustrated that bats with WNS are aroused from hibernation.  It is therefore hypothesized that the increase in body temperature and metabolism in hibernating bats results in a loss of energy.  In addition, the decrease in food availability results in the lack of nutrition and survival of bats with WNS. (Warnecke et al., IN PRESS)  Previous research has supported this hypothesis; however, there is no field evidence or laboratory evidence to support this hypothesis.  In order to test the hypothesis, a field experiment can be conducted using cameras and night vision cameras, as well as tags.  Tagging bats with both symptoms of WNS and without symptoms of WNS can provide data, such as GPS data and mortality data.   In addition, a statistical analysis can be performed between samples in order to illustrate a correlation between mortality rate and arousal rate during hibernation.

The fungus, G. destructans, was also found in European bat species; however, the mortality rates were not observed such as those in the North American bats.  The difference in mortality rates between the two continents suggests the possibility of changes in environmental conditions supporting the rate of fungal infections in North American bats. Laboratory experiments previously conducted have shown that bats in North America are more susceptible to fungal infections.  The study conducted by Warnecke et al (IN PRESS) resulted in the support of the theory that G. destructans was introduced from Europe and was responsible for the increase in mortality rates of North American bats.  In the laboratory, the mortality rates of North American bats were higher compared to European bat species treated with WNS.   It can therefore be further suggested that behavioral differences exist between the North American bat and European bat resulting in the spread of the pathogen in North American bats.  For instance, the hibernation behavior should be observed between species, such as location of hibernation, elevation, number of bats in the colony, and number of bats in a specific area.  Perhaps North American bats live in larger colonies or hibernate in closer quarters per square foot.  It can be hypothesized that a decrease in hibernation space, or increase in the number of bats per square foot, results in the spread of the fungal pathogen in the North American bat.

In order to test this hypothesis, field behavioral studies can be conducted using photographic data. Photographs of bats during hibernation can be obtained and analyzed to measure for distance in hibernating spaces between each individual bat.  In addition, the number or “clumps” or bats within a given measurement or space can be measured as well. Furthermore, the environmental conditions between North American bats and European bats should also be considered, such as elevation and temperature.  A comparison between species should be analyzed using ANOVA or correlation analysis in order to obtain statistical data to support the hypothesis.

Research has illustrated that North American bat mortality is associated with the infection of G. destructans.  Additional research has suggested a behavioral difference in the North American bat versus the European bat species.  The actual origin and mechanism causing the mortality of bats is still unknown; however, the fungus has been correlated with bat mortality.  Although the origin of the fungus is unknown, the previous studies do lead to one conclusion: the management of the pathogen and need for future research.

The life history and cause for the spread of the fungus should be further investigated.  Research into infectious diseases has shown that there are specific factors that are necessary for a disease to occur, such as a host, pathogen able to infect a host, and environmental conditions to support the host and pathogen.  Understanding the environmental conditions of the host could lead to management ideas or strategies that could prevent the spread of the disease.  For instance, researchers could locate critical habitats where the disease is most likely to occur, as well as the time frame when disease transmission is most abundant.  In addition, the need for further molecular and genetic studies in the North American bat should be addressed as well in order to evaluate specific differences between the North American bat and European bat species.  It is possible that there are immunological differences between the bat species, causing transmission of the fungus pathogen in North American bats to spread more readily.

Management of WNS in North American bats is crucial to the ecosystem.  In fact, bats are considered one of the most beneficial animals to the survival of other animals.  For instance, bats make up almost of quarter of the mammalian species in almost every habitat.  In addition, bats are predators to a huge number of insects, to include beetles and moths.  Therefore, without bats, farmers would lose crops, resulting in the loss of billions of dollars.  Furthermore, bats are important in the prevention of disease.  Bats eat mosquitoes, which can cause disease in humans. Bats also aid in pollinating flowers and dispersing seeds in rainforests and deserts.    (BLM, 2009) Therefore, much research and management into this disease is necessary for species concern and ecosystem concern.

Problem #2.  In your 2-4 page essay, discuss why would oceanographers like Hutchinson expect to ?nd low levels of diversity in a marine environment and what could be some possible reasons for high diversity in marine waters. Discuss the concepts of symbiosis and commensalism that are mentioned in the Hutchinson paper and how they differ from the Gause’s hypothesis of competitive exclusion. Also, describe Hutchinson’s conclusion in his paper and whether it supports or rejects Gause’s hypothesis.

The paper written by Hutchinson (2007) analyzes the results of laboratory findings of high species diversity from a sample of water extracted from an isolated environment, in which each species were competing for the same resource.   Hutchinson expected to find low species diversity in the one milliliter sample of water due to the principle of interspecific competition.  Interspecific competition refers to the interaction between different species resulting in competition for the same resource which limits the growth and survival of a species.  Hutchinson therefore expected to find a low species diversity index in the sample, especially being a small one milliliter sample.  In addition, the timing of the sample occurred during the summer.  For oceanographers, the summer months equal low nutrient levels with increased species competition for the nutrient resources.    Other scientists have introduced other ideas as to the outcome of the high species diversity.  It has been suggested that that homogeneity due to oceanic mixing does not occur in any marine habitat. In addition, it has been further suggested that aquatic habitats allow for a greater number of niches than originally theorized.  Furthermore, it is suggested that plankton communities do not reach an equilibrium state.

Hutchinson uses mathematical theories to explain the distribution of species in the water column, as well as to support the idea of symbiosis and commensalism.  Hutchinson indicates that a mathematical theory of competition supports the results of high diversity of organisms through the use of a specific condition permitting commensalism or symbiosis of different species in the same environment or niche.  Symbiosis is a term used to describe how organisms live together, or more like a partnership between two different species of animals.  A good example can be seen in the relationship that exists between the sea anemone and the hermit crab or the squid and a bacterium.  These species have a relationship that are long-term and benefit at least one of the species in the partnership.  This type of partnership exists because one of the species usually needs some sort of nutrition.   In the hermit crab, the sea anemones live on the outer shell of the hermit crab.  The crab becomes camouflaged, which decreases predation due to the anemone’s tentacles and the anemones get carried to other locations and are able to find food easier.  Symbiotic types of relationships can be further divided into different categories, to include commensalism.  Commensalism describes how one of the species benefits, while the other neither benefits or is affected.  An example of commensalism is observed in the remora and the shark.  The remora attaches itself to the shark.  The remora gets a free ride via the shark and eats the scraps from the shark.  The remora receives the benefit and the shark is unaffected.  (Wood, 2002)   In the current paper, Hutchinson describes the terms symbiosis and commensalism in regard to phytoplankton.  Hutchinson indicates in his paragraph on symbiosis and commensalism that some phytoplankton requires vitamins and some do not and therefore the resulting environment is a mixed population of phytoplankton.  In addition, Hutchinson describes the mobility of phytoplankton and the advantage of finding nutrients in a low nutrient environment as a type of symbiosis or commensalism.

Another scientist, Gause, proposed the theory of competitive exclusion, more commonly referred to as Gause’s hypothesis.  In this principle, it is expected that only one species would outcompete other species in the balancing of an environment and the resulting population would be a single species.  In this theory, it is predicted that species competing for the same low level resource in one type of habitat cannot coexist. (Kalmykov)  The idea that the ocean environment never meets an equilibrium state supports Gause’s theory of competitive exclusion, where multispecies interactions results in competition leading to oscillations within the water column, which further produces a higher biodiversity.  It has been shown in field studies using marine communities that exist in nonequilibrium conditions and chaotic conditions, a high interspecific competition between plankton. (Klaus, 2011)

Hutchinson (2007) concludes his paper with a general insight to examining data that analytically can be interpreted to be true, but empirically false when using theories such as competitive exclusion. The paper opened the door for scientist to research the ecology of plankton using different hypotheses, but with insight from Hutchinson’s paper.  This paper illustrated the differences in species distribution between the marine environment and the terrestrial environment, which has created huge debate on species competition in the water column of the ocean.  In addition, the paper also illustrated the need for empirical data in order to support a given theory or hypothesis.

Problem #3.  In a 2-4 page essay, discuss when and how terrestrial plants colonized land, narrate their evolutionary history from the Paleozoic era through Cenozoic era, and highlight key morphological adaptations that allowed plants to thrive on land to this day.           

The evolution of plants to land occurred in the mid-Paleozoic era, approximately between 480 to 360 million years ago. (Kenrick and Crane, 1997)  The evolution of plants from the aquatic environment to the terrestrial environment can be observed through the key morphological adaptations that plants underwent over time.  In fact, the adaptations of plants and the colonization to terrestrial environment changed the biosphere of the Earth, further developing new environments for other organisms as well.  Plants underwent many problems in order to evolve into a terrestrial environment.  For instance, plants needed to adapt to limited water availability, a decrease in mineral supply, increased effects of ultraviolet rays, changes in temperature, and exposure to a diversity of harmful microbes.  The development of evolved specialized cells and symbiotic relationships played a crucial role in the evolution of terrestrial plants.  The current paper provides an overview of the origin of plants and the evolution of aquatic plants to terrestrial environments with a focus on the morphological adaptations that promoted development on land.  (Campbell et al., 1998)

The evolution and origin of land plants are illustrated through the discovery of plant fossils from the Early Devonian Period.  Previous research conducted during the 1970s led to the analysis of data illustrating the Late Silurian and Devonian periods as the most critical point in the transformation of vascular plants.  Through this analysis, a group of fossils known as rhyniophytes were characterized as the ancestral form of vascular plants, as well as the main line of evolution from clubmosses and living vascular plants, such as ferns, seed plants and horsetails.  Through the evaluation of fossils and plant morphology, plants have been suggested to originally evolve from algae as they are most closely related to the group of fresh water green algae known as Charophycae.  For instance, plants share specific characteristics with algae, such as chloroplast with pigment cells, cellulose containing cell wall, and plastids.  The characteristics which set plants apart from algae are observed in the adaptations that plants derived for terrestrial environment life.  (Campbell et al., 1998; Kenrick and Crane, 1997)

Adaptations that plants acquired in order to survive on land are observed in their structural and chemical components.  For instance, changes in structure, such as stomata on the outside of the plant were observed in the need for photosynthetic changes for obtaining water, carbon dioxide, minerals, and light, both above the ground and below the ground.  Chemical adaptations also occurred with a waxy coating on the surface of the plant called a cuticle.    (Campbell et al., 1998)  The waxy cuticle formed in order to help the plant transition from an aquatic environment to a terrestrial environment due to air exposure in order to prevent water from escaping the plant; however, the formation of the waxy cuticle resulted in the prevention of the diffusion of necessary gases required for photosynthesis, such as oxygen and carbon dioxide.  Therefore, the evolution of stomata, small pores located on the waxy cuticle, which allowed for the diffusion of gases into and out of the plant.  (Campbell and Reece, 2002)

Other morphological changes occurred in the colonization of terrestrial plants, to include: sporophytes as the dominant generation, vascular tissue, and woody tissue.  Similar to algae, plants experience an alternation of generations; however, the ancestral algae and primitive plants consist of the haploid generation of the dominant generation.  In addition, the development of vascular tissue allowed for the increase in height in plants in order to transport material from the roots and the leaves throughout the plant. Within the vascular system, the xylem and the phloem were established.  The vascular tissue allow for water, minerals and food to be conducted throughout the plant.  Furthermore, the development of woody tissue or lignin, pollen, and seeds was observed, which help support plant’s weight and reproduce. Lignin in addition to cellulose helps provided stability and structural support. (Campbell and Reece, 2002)

It has also been suggested that the adaptation of plants to land is associated with symbiotic relationships. Theories indicate that due to the intense physical environment the first plants on land experienced, the establishment of the plants were most likely only possible due to the symbiotic relationship between a fungus and a phototroph, such as a green algae and fungus. It is suggested that lichens and cyanobacteria, along with byrophtic plants formed a crust that could withstand the harsh environmental land changes.  In addition, it is thought to have occurred in the Neoproterozoic age, about 900 to 544 million years ago. ( Heckman et al., 2001)

Scientists have divided the evolution of plants to land into four different periods.  The initial origin of plants from the aquatic environment, such as green algae, is indicated as occur in the Ordovician period at around 475 million years ago. During this period, the cuticle gametangia are thought to have evolved.  The purpose of cuticle covering on the gametangia was to protect the embryo.  In addition, the vascular tissue is said to have evolved during this period as well.  The second period occurred during the Devonian period at around 400 million years ago. During this time, the diversification of seedless vascular plants is said to have occurred, such as ferns.  The third time period occurred in the Devonian period as well at around 360 million years ago.  During the time, the development of the seed is thought to have occurred.  The seed is the plant embryo containing food reservoirs and a resistant coating.  In addition, the initial seed plants were referred to “naked seeds”.  From the naked seeds evolved the conifer plants around 200 million years ago.  The fourth and final period is known for the evolution of the flowering plants.  This occurred during the Cretaceous period approximately 130 million years ago.  Differing from gymnosperm plants, the flowering plants contain seeds within a flower, which contain ovaries.  This group was referred to as “angiosperms”.   (Campbell et al., 1999)

The adaptation of plants to terrestrial environments is also thought to have occurred from shallow water plants.  Modern day charophytes live in shallow water habitats and it is suggested that ancient charophytes also lived in this type of habitat.  Shallow water habitats experience fluctuations in water levels with the possibility of drying.  In addition, it can be noted that the change from the Ordovician period to the Silurian period experiences many climate changes, as well as changes in water levels of all types of water sources.  It can be hypothesized that natural selection could have favored shallow water plants adaptations to water and climate changes.  Furthermore an important component to the colonization of plants to land was the branching of sporophytes of the vascular plants.  The vascularization of plants allowed for the increased formation of spores and the development of more complex bodies of the plants.  The oldest fossilized vascular plant found dates back to the late Silurian and was discovered in Europe and North America.  This particular fossil was not complex; however, had branching sporophytes.  It is suggested that as the vascular plants increased in number, different species evolved. (Campbell et al., 1999)

Research studies examining the fossil records of spores have supported the theory that modern living bryophytes were the first colonizers to land.  In addition, research supports the evidence that the lineages for vascular plants evolved in the Silurian period.  (Kenrick and Crane, 1997).  With the emergence of genetic advances and techniques, scientists can now conduct genetic analyses on different plant groups and compare sequences in order to confirm lineages of plant groups, which can further help support the theories involved in the evolution of plants throughout history.

References

BLM.  (2009).  Cave Ecosystems.  Retrieved from: http://www.blm.gov/wo/st/en/res/Education_in_BLM/Learning_Landscapes/For_Teachers/science_and_children/caves/index/caves_bats.html

Campbell, N. and Reece.  Biology 6^th edition.  San Francisco, CA.

Campbell, N., et al. (1998).  Biology.5th ed. Menlo Park, California: Raven, P.H., R.F. Evert and S.E. Eichhorn. Biology of Publishers. Inc.. 1998.

Flory, A.R., Kumar, S., Stohlgren TJ, Cryan, PM. (2012).  Environmental conditions associated with bat White-Nose Syndrome mortality in the north-eastern United States.  Journal of Applied Ecology.  49:680-689.

Heckman, D.S. Geiser, D.M., Eidell B.R., Stauffer R.L., Kardos, NL, Hedges BL.  (2001). Molecular Evidence for the Early Colonization of Land by Fungi and Plants.  Science. 293:1129-1133.

Kalmykov, L.V., Vyacheslav L., Kalmykov.  A mechanistic verification of the competitive exclusion principle.

Kenrick, P. and Crane, P.  (1997).   The origin and evolution of early plants on land. Nature. 389: 33-39.

Klaus, R.  (2011).  The Paradox of the Plankton. Why do so many species co-exist in supposedly homogeneous habitats?  http://krohde.wordpress.com/article/the-paradox-of-the-plankton-xk923bc3gp4-40/.

Warnecke, L., J. M. Turner, T.K. Bollinger, J.M. Lorch, V. Misra, P.M. Cryan, G. Wibbelt, D.S. Blehert, and C.K.R. Willis. (IN PRESS). Inoculation of bats with European Geomyces destructans supports the novel pathogen hypothesis for the origin of white-nose syndrome. Proceedings of the National Academy of Sciences of the United States of America: 5.

Wood, M.  (2002).  Unit 3. Single Celled Organisms.  Retrieved from: http://www.marine.usf.edu/pjocean/packets/sp02/sp02u3.pdf

USGS.  (2012). White-Nose Syndrome Threatens the Survival of Hibernating Bats in North America.  Retrieved on 3/19/2014 from: http://www.fort.usgs.gov/WNS/.