By: JulieF,
on 8/12/2015
The agents of natural selection cause evolutionary changes in population gene pools. They include a plethora of familiar abiotic and biotic factors that affect growth, development, and reproduction in all living things.
The post The hidden side of natural selection appeared first on OUPblog.
By: Hannah Paget,
on 7/25/2014
We humans have a love-hate relationship with bugs. I’m not talking about insects — although many of us cringe at the thought of them too — but rather the bugs we can’t see, the ones that make us sick.
Sure, microorganisms give us beer, wine, cheese, and yoghurt; hardly a day goes by without most people consuming food or drink produced by microbial fermentation. And we put microbes to good use in the laboratory, as vehicles for the production of insulin and other life-saving drugs, for example.
But microbes are also responsible for much of what ails us, from annoying stomach ‘bugs’ to deadly infectious diseases such as tuberculosis and plague. Bacteria and viruses are even linked to certain cancers. Bugs are bad; antibiotics and antivirals are good. We spend billions annually trying to rid ourselves of microorganisms, and if they were to all disappear, well, all the better, right?
This is, of course, nonsense. Even the most ardent germaphobe would take a deep breath and accept the fact that we could no more survive without microbes than we could without oxygen. No matter how clean we strive to be, there are 100 trillion bacterial cells living on and within our bodies, 10 times the number of human cells that comprise ‘us’. Hundreds of different bacterial species live within our intestines, hundreds more thrive in our mouths and on our skin. Add in the resident viruses, fungi, and small animals such as worms and mites, and the human body becomes a full-blown ecosystem, a microcosm of the world around us. And like any ecosystem, if thrown off-balance bad things can happen. For example, many of our ‘good’ bacteria help us metabolize food and fight off illness. But after a prolonged course of antibiotics such bacteria can be knocked flat, and normally benign species such as ‘Clostridium difficile’ can grow out of control and cause disease.
Given the complexity of our body jungle, some researchers go as far as to propose that there is no such thing as a ‘human being’. Each of us should instead be thought of as a human-microbe symbiosis, a complex biological relationship in which neither partner can survive without the other. As disturbing a notion as this may be, one thing is indisputable: we depend on our microbiome and it depends on us.
And there is an even more fundamental way in which the survival of Homo sapiens is intimately tied to the hidden microbial majority of life. Each and every one of our 10 trillion cells betrays its microbial ancestry in harboring mitochondria, tiny subcellular factories that use oxygen to convert our food into ATP, the energy currency of all living cells. Our mitochondria are, in essence, domesticated bacteria — oxygen-consuming bacteria that took up residence inside another bacterium more than a billion years ago and never left. We know this because mitochondria possess tiny remnants of bacterium-like DNA inside them, distinct from the DNA housed in the cell nucleus. Modern genetic investigations have revealed that mitochondria are a throwback to a time before complex animals, plants, or fungi had arisen, a time when life was exclusively microbial.
As we ponder the bacterial nature of our mitochondria, it is also instructive to consider where the oxygen they so depend on actually comes from. The answer is photosynthesis. Within the cells of plants and algae are the all-important chloroplasts, green-tinged, DNA-containing factories that absorb sunlight, fix carbon dioxide, and pump oxygen into the atmosphere by the truckload. Most of the oxygen we breathe comes from the photosynthetic activities of these plants and algae—and like mitochondria, chloroplasts are derived from bacteria by symbiosis. The genetic signature written within chloroplast DNA links them to the myriad of free-living cyanobacteria drifting in the world’s oceans. Photosynthesis and respiration are the biochemical yin and yang of life on Earth. The energy that flows through chloroplasts and mitochondria connects life in the furthest corners of the biosphere.
For all our biological sophistication and intelligence, one could argue that we humans are little more than the sum of the individual cells from which we are built. And as is the case for all other complex multicellular organisms, our existence is inexorably linked to the sea of microbes that share our physical space. It is a reality we come by honestly. As we struggle to tame and exploit the microbial world, we would do well to remember that symbiosis—the living together of distinct organisms—explains both what we are and how we got here.
John Archibald is Professor of Biochemistry and Molecular Biology at Dalhousie University and a Senior Fellow of the Canadian Institute for Advanced Research, Program in Integrated Microbial Biodiversity. He is an Associate Editor for Genome Biology & Evolution and an Editorial Board Member of various scientific journals, including Current Biology, Eukaryotic Cell, and BMC Biology. He is the author of One Plus One Equals One: Symbiosis and the Evolution of Complex Life.
Image credit: Virus Microbiology. Public domain via Pixabay
The post Microbes matter appeared first on OUPblog.
By: ChloeF,
on 6/27/2014
Coral reefs are the most diverse ecosystem in the sea. In some ways they are very robust marine ecosystems, but in other ways, perhaps because of their huge numbers of species, they are very delicate and susceptible to being damaged or killed. On the one hand, healthy reefs are glorious riots of life, and marine scientists have spent several decades unravelling the complicated ways in which they work. On the other hand, at least one third of the world’s reefs have already died — gone for ever in terms of human lifetimes at least — even when the cause of their demise is lifted.
How coral reefs lived and grew right up to the sea surface remained a mystery for years for several reasons. First, where were all their plants? It was known that plants are the world’s food base, yet there were hardly any visible plants, let alone waving fields of them such as the naturalists knew about from their own (mostly cold) Northern shores. The answer is that the main plant base comes from the symbiotic algae living in the cells of reef building corals. This helped answer the second mystery: how could such vibrant reefs live in the nutrient-poor oceans of the tropics? Nutrients, it was known, were needed for plants to grow. But the waters that bathe oceanic reefs in particular were the poorest on Earth in terms of nutrients. The answer was clear once the symbiosis was discovered; there is a very tight cycling of nutrients between the symbiotic components of the coral-algal symbiosis and little ‘leakage’ from the reef into the sea.
There was a third, long running mystery also, namely, how do reefs form? In particular, why do they invariably grow to the surface of the sea from a wide range of depths and, why do they all have rather similar shapes? This was explained in several ways. Firstly it became clear that the Earth’s crust moves, both across oceanic distances over huge time periods, and they move vertically by hundreds of metres. Corals need light (because of their symbiotic algae) so they only live at the contemporary sea level, and the sea level changed hugely over the millennia that corals have lived and made their limestone skeletons. Darwin was the first to deduce this, in particular the importance of growth on subsiding substrates such as volcanoes.
The numerous shapes and kinds of corals, soft corals, and sponges (and many other forms) live together in what has been called a ‘super-symbiosis’ or a ‘super-organism’, terms which, while strictly not true, do give a sense of the intimate linkages that occur between so many of the component groups of species. This may provide one reason why they are, in so many ways, very susceptible to human impacts today. Raised nutrients (e.g. from sewage and shoreline construction) are hugely damaging. Burial of reefs for building on are also fatal to the reefs of course, and, sadly land made by landfill on a reef foundation (something easy to do because reefs are shallow) has a higher economic price when sold for building than the reef did in the first place. Shallow sea and reefs, we might say, become more valuable when they are no longer sea but are converted to expensive, sea-side building land! Eco-nomics and eco-logy have the same root word and should work hand-in-hand, but clearly they don’t, to the detriment of these complex living systems.
Reefs are valuable – but to whom? Reef and beach based tourism forms over half the foreign exchange earnings for many countries. Without reefs to attract tourists, many states would become impoverished; many already are. More importantly (again to whom?) they provide food for huge numbers of coastal dwellers throughout the poorest parts of the world. Not only do fish form the basis for human existence, but so do molluscs, sea cucumbers, octopus… the list is endless. Too many people extracting food from a reef readily collapses the elaborate ecosystem, with the result that there is nothing left for the next year, or the next generation.
Various aspects of climate change are adding to the mix of stresses for reefs. As CO2 builds up, it warms the oceans, and this has killed off countless areas of reef already or at least added an additional stress. When that gas dissolves in the ocean, the water becomes more acidic, again causing damaging effects, in this case reducing the ability to lay down their limestone skeletons. These are not predicted effects – something for the future. We measure it and know that we are already well along that path.
Coral reefs are a canary in the environmental coal mine, showing us, before any other system can perhaps, what we are doing to the earth today. We know enough of their science now to understand this and avert the problems. What we don’t have is the will to do so. It is no longer a problem of science but of sociology and politics.
Charles Sheppard is Professor in the School of Life Sciences at the University of Warwick. His research focuses mainly on community ecology, particularly on ecosystem responses to climate change. He works for a number of UN, Governmental, and aid agencies to advise on topical marine and costal developmental issues. He is the author or editor of 10 books, including The Biology of Coral Reefs (2009) and Coral Reefs: A Very Short Introduction (2014).
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Image credit: Iolanda reef in Ras Muhammad nature park (Sinai, Egypt), By Mikhail Rogov, CC-BY-SA-3.0 via Wikimedia Commons
The post Coral reef stresses appeared first on OUPblog.
By: Tasha Saecker,
on 6/1/2010
How to Clean a Hippopotamus by Steve Jenkins and Robin Page
A fascinating tour through symbiotic relationships in the animal kingdom, this book uses comic book frames and short text bubbles to become incredibly appealing to reluctant readers. Filled with Jenkins’ paperwork illustrations that offer clarity beyond that of photographs, this book is a visual treat. It is also filled with interesting facts, and is sure to surprise even the most informed reader with several of the relationships inside. Journey through symbiotic relationships where one animal cleans another one to others where enemies become friends and supporters for a time. Get this one into the hands of children who love animals and struggle with books, they are sure to feel right at home here.
Jenkins’ art is done with such confidence and cleverness. His use of fuzzy papers to get the feel of fur, of color to get the feel of skin, and of pattern to get the texture right really take him beyond most other paper artists in children’s books today. The fact that he manages to capture what an animal actually looks like is amazing. Animals have a light in their eyes, a focus and in this book a relationship with each other, all captured with paper.
The facts here are done with just the right amount of text and a playful, interested tone. The book invites readers in and marvels alongside them. The design here is wonderfully done, breaking what could have been paragraphs of text to wade through into windows of color filled with bite-sized bits of text that get readers wanting more.
Highly recommended, every library needs this book on their shelves. Guaranteed to go home over and over again. Appropriate for ages 5-9.
Reviewed from library copy.
Check out another review at A Patchwork of Books.
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