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.
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) increases the kinetic energy of molecules and thereby the rate of collisions between enzyme active sites and substrate molecules, once the optimum temperature threshold has been breached, an enzyme is no longer capable of functioning as efficiently. This could lead to denaturation (though unlikely without a significant increase in mean environmental temperature), whereby molecular bonds within the enzymes structure are now broken thereby disrupting the tertiary/ quaternary structure of the polypeptide, making it useless in the catalysis of biochemical reactions. Now, whilst one may be thinking that such an idea is far-fetched in the context of global warming effects on global temperatures because the incremental increases are far too small. Whilst this may hold true in the short term for a large number of organisms, it isn’t strictly true of all. For example, in the Great Barrier Reef, mass coral bleaching incidents have occurred in recent years, with as much as 90% of corals being somewhat affected, in part due to the effects that temperature increases have had on the enzymes and polypeptides of coral polyps, but also expulsion of certain symbiotic protozoa and zooxanthellae. The tropical ocean, being the natural environment of coral polyps, is one whose temperature variation is marginal throughout the course of the year, and therefore these organisms have adapted to withstand only a small variational margin in surrounding water temperature. It is for this reason then that polypeptidal pigments and the enzymes which synthesise them are so readily denatured when an extreme temperature in the surrounding water occurs, leaving only behind a calcium based ‘skeleton’ of what was once a habitat of indescribable natural beauty.
