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Category Archives: Biology

Earthworms – A Great Bunch of Lads

There has been a lot of publicity over the last few years regarding the massive contribution of bees to biodiversity and food production across the globe and the dire consequences we should expect now that their numbers are literally dropping like flies, due to disease and pesticides.

But they are not the only creatures driving on agriculture in this way. They may not even be the biggest contributors to boosting food production. While bees a busy working in the air, there is another force of nature working tirelessly is a subterranean metropolis.

A major habitat upon which agriculture heavily relies is the soil which supports the vast majority of farming in the world, whether it be crop growing, livestock feed, forestry or simply paddocks. Good quality soil provides a valuable resource for farmers but even the soil relies on other factors to keep itself in good condition, such is the nature of a diverse ecosystem. The flora and fauna of a soil perform countless acts, each contributing to the delicate balance, keeping it in top condition. Perhaps the best known of these is the earthworm. Without the earthworms soil is generally of a much lower quality and with their help the soil is happy which keeps the farmer happy. But do the farmers return the favour?

Earthworm_Jim_by_Trebeck

Earthworms carry out a number of functions in the soil, even if they don’t know it. They are just going about their own worming business but in doing so they have a knock on effect that impacts on those above the soil. They vastly mix up the soil by carrying up new soil from deep down and by carrying organic matter down deeper into the soil in their gut. Each year worms bring up 10-20 tonnes of earth per acre. Not only do the worms distribute the nutrients, both organic and inorganic, but they also aid in the uptake of these nutrients by plants. Simply by burrowing they provide the plant roots with tracks to follow, requiring less effort on the plants part. As well as this, the tracks aerate the soil, important for nitrogen fixation and provide drainage. This can particularly important in avoiding surface water.

earthworm_in_burrow

Earthworm Society of Britain

Where earthworms have diminished, dramatic reductions in soil porosity have been identified with consequent lower water infiltration and a significant build up of un-decomposed surface matter was observed on Dutch farms where the earthworms and other soil fauna were no longer present.

The actions of farmers, however, may actually be discouraging the growth of earthworms. For example, it has been shown that ploughing land can dramatically reduce the numbers of earthworms and other soil invertebrates. The earthworms can also come under chemical attack from overuse of fertilizers and pesticides, also affecting a range of other organisms which the chemicals do not target. This highlights the importance of thoughtful practice on farmers behalf as their actions can have long lasting and sometimes irreversible effects on the local biodiversity.

No measures have been introduced to protect the soil biota specifically despite its overwhelming importance to agriculture. However, the EU nitrates directive and various water quality acts have contributed to cleaning the earthworm’s environment. Of course the world is not completely ignorant of the importance of earthworms, it is even possible to buy batches of them to improve soil or for compost heaps and there are actions farmers can take to promote earthworm numbers in their land. If the farmers were to reduce the nitrogen spread on the land and instead plant clover in their grassland, they can have the benefit of the clovers nitrogen fixation abilities and also reduce cost by saving on fertilizer. This way the clover can be included in silage for winter and the earthworms are free from artificial chemical surplus in the soil.

I think it’s fair to say that the contribution of earthworms to the economy is greatly underestimated. The contribution is in the billions of euro/dollars when you take into account the amount of trade that stems from the land (livestock, tillage, crops etc.). It also suggests that the presence of earthworms increases forage production by 25% when compared to production in the absence of worms.

In a world where population is predicted to dramatically increase over the next few decades, especially with the emergence of major new Asian economies, the strain on land resources is going to increase to breaking point. Techniques that are sustainable to soils need the contribution of earthworms should be investigated closely as the over use of fertilizers on such a large scale can leave the planet in a state that can only lead to disaster and large scale famine. The techniques currently used for intensive farming are not conducive to earthworm growth and as highlighted they are far more useful to the farmer alive than absent.

Is it any wonder Darwin himself said of earthworms;

‘It may be doubted whether there are many other animals which have played so important a part in the history of the world, as have these lowly organized creatures.’

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Posted by on June 22, 2013 in Biology

 

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How Human Evolution Might Destroy Us

I read a few things this week that might get you thinking about where we might be going as a race.

I read the classic sci-fi novel ‘The Time Machine’ by H.G. Wells in which a scientist builds a time machine and travels 800,000 years into the future. Given the time scale, the Time Traveller naturally expects a world very different from our own. Like most people, he expects a highly advanced society with unimaginable technologies. Wells, on the other hand, wrote a very different future.

Timemachinebook

He describes how the human race has split into two species, neither of which are anything to look forward to. One species, the Eloi, essentially pushed the other, the Morlocks, underground to work for them. Over the generations, in the absence of any need for physical exertion, as diseases are eliminated and with the Morlocks providing for them, the Eloi gradually lose the need for strong bodies and intelligence in everyday life. As a result, they evolve to become almost childlike in both appearance and mentality. They have become victims of their own success by eliminating the problems that keep their minds and bodies active.

Then I read an article by Stephen Baxter in the BBC’s Focus science magazine (Apr, 2013) in which he discusses the possibility of human subspecies evolving. He mentions a few different ways in which this might happen such as colonies on different planets or genetic engineering. Regardless of how it happens, the most likely result of developing two human subspecies is war.

It is hoped that future humans will have the intelligence to avoid conflict but, looking at the state of the world today, this is debatable. Baxter references ‘On The Origin Of Species’ as saying that similar species, i.e. from the same genus (Homo for us humans), are in fact more like to conflict with each other as they are more likely to compete for the same resources. This is one of the most common explanations given for contributing to the demise of the Neanderthals.

neandertallica-art

Even today, this strikes a chord as conflict between human races and nationalities are often over competition for resources. For example, immigrants are often given a hard time for ‘taking our jobs’ or ‘our women’, sometimes leading to conflict.

Given the fate of the Eloi in ‘The Time Machine’, is it wise that we can have food delivered to our door, use machines to carry us on long journeys (and short ones) or that we depend so heavily on electronics to do much of our thinking for us such as remembering important dates and relying on them to remind us of them?

By using technology to make our lives easier, are we slowly making ourselves dumber and weaker as a race?

And if there is ever another species to compete with, will we have the capacity to outsmart them? Or will we go the way of the Neanderthals – into the history books? Or the way of the Morlocks – into slavery?

 
 

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Bacteria – The Ultimate Survivors

bigstockphoto_Coli_Bacteria_1490456

Judgment Day – The human race is dying off. The rivers are drying up, crops are failing and the soil barren. The atmosphere is so thick with pollutants and dust that the sun no longer penetrates to the surface of the earth, cutting off the main energy source of the biosphere. Man is doomed, the world an inhospitable environment. There is no food, no water and the very air is a deadly poison. Death is the only fate for the race…. but what if it didn’t have to be?

What if we could preserve the race in suspended animation to return only when the environment has recovered and can again support life? Even if this takes centuries to happen and in the mean time you are exposed to unbearable heat, toxic chemicals, drought, starvation, nuclear radiation exposure and the wear and tear of time as the years pass. Wishful thinking. This is impossible and can never happen. Well, maybe not for us human beings but for two gram positive genera of bacteria this is a reality. Both the Clostridium and Bacillus genera have the amazing ability to ensure the survival of their kind by preserving their DNA in an impenetrable and almost indestructible capsule called an endospore.

This last resort is only used when absolutely necessary, after all other attempts at survival are unsuccessful. When a bacterium can no longer survive in an environment, it copies it’s DNA and creates the enduring endospore to protect it. This DNA can survive for years until conditions are favourable outside again. It is a sacrificial process whereby if the bacterium does begin the process of sporulation, it will die in the process. The organisms DNA is preserved however, ensuring the survival of the strain. The resulting germinated bacterium is merely a clone of the original.

Endospore

With Bacilli being aerobic and Clostridium being anaerobic, these spores are produced by a wide range of bacteria. A major problem with endospores, in regard to everyday life for humans, is in the preservation of food. Scientists have had to develop ways of destroying endospores present on food or ways of ensuring they cannot germinate. Unfortunately, the majority of endospore forming bacteria are pathogens. Therefore, the consumption of endospores creates a health risk as there is no better environment to bring about germination than the warm, moist intestines of a mammalian body. Infant botulism is a prime example of this. The endospores of Clostridium botulinum can be found in honey where they are unable to germinate due to the excessive sugar levels. If an adult consumes the spores in the honey they are unaffected because the spores cannot tolerate the strong acid in the stomach and the abundance of intestinal flora already present. If an infant under twelve months were to eat the honey however, the spores would find themselves in the ideal environment for germination as the stomach acid is weaker and the natural flora not yet established. Infant botulism can lead to respiratory failure and even death if not treated.  Another high profile case of the dangers of this property of endospores than the anthrax scare in the USA in 2001. There was widespread panic when endospores of Bacillus anthracis were posted in envelopes causing several deaths as the inhaled spores quickly germinated and led to respiratory failure. One worry is that as well as Bacillus anthricis, many of the endospore producing bacteria can be used in biological warfare, including Clostridium Botulinum. The Bacillus anthracis also has a habit of lying dormant in soil for years until it unexpectedly germinates causing damage to livestock and humans alike.

It is widely accepted that some endospores can lay dormant for centuries waiting for conditions to become favourable again but there are cases of germination in the lab of endospores dating back several thousand years. Using the appropriate growth medium and aseptic technique scientists have been able to germinate Clostridium endospores found in the ancient tombs of Egypt. These tombs are approximately 4000 years old. Even more amazingly in 1995 the scientist Raúl Cano managed to germinate Bacillus sphaericus endospores found in the gut of a 30 million year old bee preserved in amber found in Dominica.

Whereas this is a significant scientific find, it does not quite signal the time for a real life Jurassic Park being made possible. It is the bacteria which come back but there is no DNA from other organisms which could be used to clone and grow new creatures (or old creatures as the case may be) even if the technology to do so was available. Unbelievably some scientists even claim to have germinated endospores that date back 250 million years though these claims have been met with scepticism and need to be verified (Vreeland, R. H., W. D. Rosenzweig, and D. W. Powers. 2000).

But what is an endospore? How can an organic specimen endure such rigours for such a long time with next to no metabolic activity and still maintain life to return and go on as normal? To answer this it’s important to understand the structure of an endospore. An endospore is a dry, non-dividing, metabolically almost inactive and dormant cell that is produced to preserve DNA by a moist, metabolically active, vegetative bacterial cell when it detects that it can no longer survive in its current environment.

It is amazing to think that a bacterium can become almost invincible in just eight hours, survive like that potentially for centuries and then return to normal in a mere hour.

With this remarkable resilience to survive almost any kind of attack added to the bacterial arsenal, is it any wonder they are found in almost any environment in the world. They can get energy from a variety of sources, through both heterotrophism and autotrophism. From the sun to volcanic springs at the bottom of the ocean under extreme pressure. They can live straight off raw chemicals in the case of chemotrophs. They can survive in the absence of oxygen, mutate almost on demand if they encounter any new problems. This includes new food sources and new powerful antibiotics. The bacteria can simply alter their DNA to resist the drug and to produce new enzymes that can break down the new food source. Is it any wonder bacteria are referred to as “The Ultimate Survivors”?

 
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Posted by on December 17, 2012 in Biology

 

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