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Ecological Interaction Of Humans And Reptiles Environmental Sciences Essay

Ecological interaction is the relation between species that live together in a community; specifically, the effect an individual of one species may exert on an individual of another species.

Reptiles and amphibians seems not to play a very significant role in the sustainability of human life on earth but deeper research into the roles of these organisms indicates that they are of importance. There are various ecological threats which can affect reptiles. Habitat loss and destruction is a major ecological issue affecting reptilian species. Habitat loss is widely recognized as the leading threat to global biodiversity. While difficult to specifically categorize, habitat loss take places on an overlapping range from small-scale to large-scale and from absolute destruction to subtle degradation. There are many factors which contribute to this phenomena. Activities such as mining, logging, shifting cultivation and clearing of plots of land can pose threat to the natural habitats of many herpes. This promotes migration of species from one area to another thus reducing the diversity of the area.

Climate change is another implication which can influence the lives of herpes and reptiles. Climate change responses will be influenced by a number of factors: (1) expected changes and inconsistency in local environmental and habitat conditions; (2) the phenology (timing) of life-requisite activities; (3) interactions with emerging pathogens and invasive species; and (4) interactions with other environmental stressors (e.g., chemicals). Over the short term (e.g., annually), the interaction of these factors will determine reproductive success rates and survival to metamorphosis. Over the long term, the regularity and extent of extreme temperature and precipitation events will likely influence the persistence of local populations, distribution capabilities and thus the structure of meta-populations on the landscape.

Alternation in air and water temperature, precipitation, and the hydro period (Carey and Alexander 2003) tends to affect amphibian and reptilian species since they are highly sensitive to and respond strongly to these changes. This is due to them being ectotherms; their body temperature depends on most favorable environmental condition. Amphibians require aquatic and moist habitat for laying egg and larval development and post metamorphic life stages respectively. Amphibians are more likely to experience lower survival rate to metamorphosis as the temperature warms and variability of water proceed.

Species related with ephemeral waters, such as low ponds and alternating streams may be predominantly susceptible to altered precipitation patterns. Temperatures outside of their thermal optima will also cause physiological stresses. Some reptile species exhibit temperature-dependent sex determination during egg incubation that could be influenced by changes and variability in global climate.Because of their affinities to aquatic habitats and their small size, amphibians typically have relatively small home ranges and low dispersal rates. Reptiles are more mobile and have a greater ability to withstand the expected dryer and warmer conditions. However, because key habitats and species ranges have already been altered and fragmented by human use and development, the physical pathways to connect animals with suitable habitats (e.g., upwards in latitude or elevation) may not exist.

Direct ecological interactions between herpes includes: niche differenciation(resource partitioning), predation and competition. Niche differenciationrefers to the process by which natural selection drives competing species into different patterns of resource use or different niches. This causes one specie to partition resource with another so that one does not totally out compete the other, consequently coexistence is achieved through the differentiation of their realized ecological niches. Niche partitioning may not occur if there is sufficient geographic and ecological space for organisms to expand into. A typical example of resource partitioning is shown by the  Anolis lizards in the tropical rainforest. Although they share common food needs — mainly insect, they evade competition by residing in different parts of the rainforest. Some live on the leaf litter floor while others live on shady branches, thereby avoiding competition over food in those sections of the forest. Resourse partitioning is a type of niche differentiation. Resource partitioning occurs when biological species require different parts of the same resource.

Human interactions with amphibian populations.

Human beings have impacted almost on every living creature on earth both directly and indirectly. Humans have interacted with amphibians since antiquity. Some of these exchanges are direct and easily understood while other connections are more difficult to discern. Human activity has caused the disappearance of many animal species, the deaths and diseases of others and as a result, pose major a threat to the earth’s biodiversity.

Due to human interactions, many there has been dramatic declines in amphibian populations, including population crashes and mass localized extinctions, have been noted since the 1980s from locations all over the world. These declines are perceived as one of the most critical threats to global biodiversity, and several causes are believed to be involved, including, over exploiataion, pollution and chemical use, habitat destruction and modification, climate change, and increased ultraviolet-B radiation (UV-B).

Human interactions can be direct and indirect.

Direct interactions with amphibians: this involves directly taking species of amphibians which includes frogs, toads, salamanders, newts and using them for commercial and economic purposes. One direct human interaction is over exploitation.

As with many other resources that humans consume and over exploit, Amphibian species are no exception. Frogs are commercially important for their food value. The legs of some bullfrog species are in heavy demand in China, Europe (especially France) and in parts of the United States, especially Louisiana. The worldwide harvest is an estimated 200 million bullfrogs (about 10,000 metric tons) annually. Major bullfrog suppliers include Bangladesh, China, Indonesia, and Japan, with about 80 million collected each year from rice fields in Bangladesh alone. As a result, populations have fallen drastically from excessive exploitation (Economic and Ecologic Importance of Amphibians: Investigating the Connections Between Amphibians and Humans) http://www.suite101.com/content/amphibianhuman-interactions-a179036#ixzz15aCfnKk6)

In addition, many amphibian species are removed from the wild to be used as pets, and to supply biological markets. This exploitation of species has also lead to mass decline of amphibian populations.

Indirect human interactions: these include all the activities that human beings do to alter the environment,which intern affects all animal populations and global biodiversity.

The current global loss of species is a process generated by the activities of humans. As we modify our environment for our own ends, it is clear that the destruction of the habitats of other species leads directly to their disappearance. Indirect human interactions, that has lead to mass decline includes:

Water quality factors( mainly caused by pollution and chemical use):

Many water ways are polluted by human activities especially agricultural and industrial activities. These pollutants contaminate the water ways that many amphibians use as habitats and since amphibians have permeable, exposed skin and eggs that may readily absorb toxic substances from the environment. Their eggs are laid in water or in moist areas, and their larvae (tadpoles) are aquatic. Because amphibians are intimately tied to an aquatic environment, the quality of the water in which they live can affect their growth, development, and survival. Because pollutants, waterborne pathogens, and global environmental changes can all affect water quality, these factors can in turn affect amphibians. Conversely, amphibians are important indicators of water quality, and are considered a sentinel species, meaning that what affects amphibians presently may affect other animal species in the future.

Acidification.

A number of studies have shown that acidification of fresh water (that is, a reduction in pH to acidic levels) via acid rain, acid snowmelt, or other modes of pollution are harmful to amphibian growth and development. Some species are more tolerant of acid conditions than others. Thus, depending on the species, the amount of acidity, and other environmental variables, amphibians may experience developmental deformities and increased mortality due to acidification.

Acidification potentially affects amphibian populations and the communities in which amphibians live. For example, some populations of toads in Britain have probably been reduced by water acidification. Salamander populations in Colorado seem to have declined because of increased acidification during snowmelt. Several studies have shown that acidification of the water can affect competition and predation between amphibians. Thus, the larvae of some frog species may have increased survival rates under acid conditions because their salamander predators show reduced predation at low pH.

Nitrates and Nitrites.

Many chemical products used in agriculture and industry pollute aquatic habitats, causing potentially severe damage to ecosystems. For example, the increase in concentration of nitrate in surface water on agricultural land due to numerous sources may be hazardous to many species of fish,

Toxic Substances.

Just as amphibian species display variation in sensitivity to nitrate-related compounds, they also show variation in tolerance to other toxic substances that may be found in water. Insecticides such as organophosphates, carbonates, and synthetic pyrethroids, which are used mainly in crop production, have a wide array of effects on amphibians. Depending on the concentrations used and the species involved, some of these substances may be lethal, may affect growth and development, or may affect metamorphosis.

Habitat modification alteration and fragmentation.

Habitat modification or destruction includes the construction of infrastructure and roads, mining and logging activities etc. and is one of the most dramatic issues affecting amphibian species worldwide. As amphibians generally need aquatic and terrestrial habitats to survive, threats to either habitat can affect populations. Hence, amphibians may be more vulnerable to habitat modification than organisms that only require one habitat type. Large scale climate changes may further be modifying aquatic habitats, preventing amphibians from spawning altogether.

Climate change

Anthropogenic global warming has unequivocally exerted a major effect on amphibian declines. For example, in the Monteverde Cloud Forest, a series of unusually warm years led to the mass disappearances of the Monteverde Harlequin frog and the Golden Toad.(decline_in_amphibian _populations.com). An increased level of cloud cover, which has warmed the nights and cooled down daytime temperatures in an attempt to control global warming, has been blamed for facilitating the growth and proliferation of the fungus Batrachochytrium dendrobatidis (the causative agent of the fungal infection chytridiomycosis.

Chytridiomycosis or Chytrid Fungus is an epizootic and a major contributor to the decline of amphibian populations around the world, threatening many species with extinction. 

This fungus is a global emerging amphibian pathogen which is proving to be one of the worst vertebrate infectious diseases found so far. It is causing a huge amount of extinction and disease within amphibian populations. More than 100 species of amphibians are known to be affected by the chytrid fungus (Batrachochytrium dendrobatidis). Some are very susceptible and die quickly while others which are more resistant are carriers of the pathogen.

This disease is already credited with wiping out frogs and toads in large numbers in Australia and South America. (decline_in_amphibian _populations.com)

The increased temperature caused by global warming has also caused the disappearance of many species from increasingly hot habitats. The rise in sea levels which causes consequent flooding and destruction of habitat has also lead to extinction of some species.

Ultra violet radiation

Levels of UV-B radiation in the atmosphere have risen significantly over the past few decades, due to stratospheric ozone depletion and climate change. Researchers have found that UV-B radiation can kill amphibians directly, cause sublethal effects such as slowed growth rates and immune dysfunction. The amount of damage depends upon the life stage, the species type and other environmental parameters. Salamanders and frogs that produce less photolyase, an enzyme that counteracts DNA damage from UVB, are more susceptible to the effects of loss of the ozone layer. Exposure to ultraviolet radiation may not kill a particular species or life stage but may cause severe damage to it.

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