Geological uplift creates mountain biodiversity hotspots

Mountains tend to have more species than valleys, and new research provides support for the theory that mountain formation itself might be responsible.

Yaowu Ying and Richard Ree from The Field Museum in Chicago compared regional rates of plant colonisation and speciation in the Qinghai-Tibetan plateau, a high-altitude biodiversity hotspot. Within the QTP, the Hengduan mountain region is the most biodiverse, harbouring an astonishing 12,000 species in just 500,000 km2. The authors used published datasets to compare the spread of over 4,500 plant species across Hengduan, the Central Asian Mountains and the Himalayas.

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Bacterial Threesome Throws up Evolutionary Surprise

Symbiotic relationships, where two organisms ‘live together’ and rely upon each other to survive, are surprisingly common in the animal kingdom. The more we look, the more we find. What is less common, or at least less well documented, is the occurrence of speciation events within these partnerships. A recent study has revealed the first documented case of the speciation of a bacterial symbiont, inside the cells of a cicada. Even more interestingly, scientists believe it may have been little more than an evolutionary screw-up!

Symbiotic relationships can be quite casual, or extremely intimate, and are literally all around you. And inside you. The mitochondria inside your cells are symbiotic bacteria that joined our cells billions of years ago. Mitochondria show a pattern that is common in such intimate symbiotic relationships – over millions of years, partners in the relationship each have a reduced genome, with a complementary set of genes. This in turn makes them even more dependent upon each other. Mitochondria have only about 37 genes, compared to 1000 in a free-living bacteria. They simply don’t need many of their genes anymore because their host cells carry them. This is known as relaxed selection – because both members of the partnership carry the genes, a mutation in a gene in one partner will probably have no effect. The other member still has a functioning version of that gene, so the organism as a whole shows no negative symptoms, and natural selection is blind to the mutation. Only when both copies of a particular gene are degraded will natural selection step in, meaning that over time random chance will degrade complementary sections of each genome.

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What Makes Us Human Part I
A Brief History

The earliest known hominid was Sahelanthropus tchadensis, represented only by relatively few fossilised skull fragments, he is so ancient it isn’t clear whether he could truly be considered human at all. Fossils found in Chad, dated to around 7 million years old, may have belonged to a direct human ancestor, or more likely to a neighbouring branch of the ape family tree. This uncertainty is common until around 4 million years ago; many species are known only by partial skeletons and the relationships between them are often unclear. The Australopithecines may be the first group of hominids that we can be said to understand to any extent.

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Reasons Why Evolution is True Part VI:
Homology

Although it makes sense to stick with a good idea when you’ve found it, you wouldn’t stubbornly stick to the same design even when it wasn’t quite working properly, would you? And yet this is just the pattern that appears in nature. Life on Earth shares a remarkable list of features, from protein-handedness and membrane structure to the DNA code. While some of these features, such as protein-handedness (which way around proteins are formed), are inconsequential, others are not. The genetic code is almost completely universal across all life. This is the reason GM can work, because a gene coded for in the genome of one species can be read by the translation machinery in another species’ cells. This does not necessarily have to be true, however, as the code is arbitrary and there are many possible configurations which would work equally well. Furthermore, the code is actually detrimental for some species living in extreme environments, since certain codes are more volatile than others. Despite this, the code is shared by all.

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Reasons Why Evolution is True Part IV:
Galapagos Finches

For most biologists and reasonable people, evolution is FACT. In as much as gravity could be said to be fact. However, for those who deny the existence of evolution, the difficulty of observing its occurrence in real time is proof enough that it doesn’t exist. There are a few key examples of evolution in action, however, and during these short essays I have been detailing some of them. One of the most famous examples is that of the Galapagos Finches, which inspired Darwin as he formulated his ground-breaking theory.

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Reasons Why Evolution is True Part III:
Ring Species

One common argument proposed against evolution is that we cannot see speciation in action, and thus cannot know for certain that it happens. To say that this claim is false is an understatement. Artificial selection, both in terms of the range of domestic species produced by humans over the last 10,000 years, and artificially selected laboratory populations of bacteria, insects and small mammals, certainly go a long way to prove that natural selection and speciation are possible. But does it occur in nature?

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All-Female Fish Species takes Males for a Ride

Reproduction takes two… right? This is true for most animal species, with reproduction involving the fusion of a sperm and an egg. However, one fish species has taken a different approach. The Amazon Molly is entirely female. When they are ready to reproduce, members of this species must find a male of another, related species, and mate with him. However, instead of using the sperm from this male to provide half of the genetic information for the future offspring, the female Amazon Molly merely uses the sperm as a signal to trigger embryogenesis, in a process known as gynogenesis.

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