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Mean temperatures are rising in many parts of the world. The resulting temperatures may result in physiological and ecological effects on living organisms. Describe and explain these effects.

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Introduction

Mean temperatures are rising in many parts of the world. The resulting temperatures may result in physiological and ecological effects on living organisms. Describe and explain these effects. (25 marks) The almost undisputed effect of anthropic derived increase in global greenhouse gas emissions causing so called 'global warming' has indeed led to many increases in mean temperature records in recent years, with almost 5 of the top 10 hottest years on record occurring in the past decade. This in turn is having, and will continue to have, affects a wide spectrum of organisms, not only because it has the potential to affect an organism's biology/ physiology, but because changes to physiology coupled with newer environmental selection pressures will inevitably change a populations gene pool in turn changing their environment and ecological interactions with other organisms. Let us begin by addressing the immediate physiological effects of an increase in mean temperature. Perhaps the most import aspect one should consider is the effect of temperature on the various metabolic pathways in living organisms, notably those involving enzymes. All organisms' enzymes have optimum temperatures at which they function best. Therefore whilst an increase in bodily temperature (a result of increase in environmental temperature) ...read more.

Middle

but also to other factors such as various chemical concentrations and water potentials of tissues (to maintain metabolic pathways and to prevent cells undergoing osmoticlysis if tissue fluid is hypo/hypertonic in the case of water potential maintenance). In terms of an increase in environmental temperature, this of course in turn causes an increase in blood temperature. The increase in blood temperature is detected by thermoreceptors in the hypothalamus, which in turn sends impulses via the autonomic nervous system (as thermoregulation occurs below conscious knowledge) to the heat loss centre (which controls the mechanisms that decrease body temperature), also located in the hypothalamus. This in turn sends impulses to the effector organ whence a number of physiological changes may occur to then attempt to lower body temperature, besides a number of semibehavioural mechanisms, such as moving towards shaded areas. One heat loss pathway is to increase sweating; to evaporate water from the surface of the skin requires heat energy from the body. Hair erector muscles within the skin relax, causing an increase in the elasticity of the skin which makes the hairs flatten against the body. This reduces the thickness of the insulating layer of air and therefore allows more heat to be lost to the environment by means of convection. ...read more.

Conclusion

In this case, individuals with genotypes coding for short/ sparse coats have the advantage, as we have already seen; they will produce a smaller insulating layer of air around the surface of the skin thereby being able to lose more heat via radiation. However, those to the right of the mean, ie with genotypes coding for long/ thick coats will have a larger insulating layer and therefore require more energy to be used through the various homeostasis inducing processes such as vasodilation and evaporation of sweat. These individuals must therefore spend more time seeking food to supply this increased energy requirement, whilst the well adapted individuals can spend more time breeding. As a result, the gene pool becomes more frequent in the alleles for the shorter fur length, and when displayed as a normal distribution, this would have the effect of shifting the curve to the left, and also extending it across the y axis, for individuals at the extreme ends of the spectrum never pass on their alleles, leaving more of the resources available in the ecosystem to the well adapted individuals. In conclusion, whilst mean temperature rises globallyonly amount to small incremental changes in the short term, this nonetheless has significant impacts for organisms' physiology on a short term basis, but also affects whole ecosystems in the long term as population variation changes to accommodate the changes to the environmental abiotic factors. ...read more.

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