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The Importance of Size in the Evolution of Complexity in Ants

Tue, 16 Sep 2014 10:14:37 +0000

Ants are amongst the most abundant and successful species on Earth. They live in complex, cooperative societies, construct elaborate homes and exhibit many of the hallmarks of our own society. Some ants farm crops, others tend livestock. Many species have a major impact on the ecosystems they live in, dispersing seeds, consuming huge quantities of […]

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Understanding Catfish Colonisation and Diversification in The Great African Lakes

Fri, 05 Sep 2014 10:29:42 +0000

Why some regions or habitats contain vast, diverse communities of species, whilst others contain only relatively few species, continues to be the subject of scientific research attempting to understand the processes and conditions that allow and adaptive radiation. The Great African Lakes exist as freshwater ‘islands’, with spectacularly high levels of biodiversity and endemism. They […]

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Sex Differentiation Begins During Early Development

Wed, 27 Aug 2014 14:04:57 +0000

Males and females look different from each other, and these sexual dimorphisms are the result, largely, of sex differences in the expression of certain genes. Typically, scientists have studied sexual dimorphism in sexually mature adult animals, as this is the lifestage where differences are most apparent. However, many sex-specific phenotypes arise from sex-biased development, so […]

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Extinction and Species Declines:Defaunation in the Anthropocene

Mon, 18 Aug 2014 10:35:52 +0000

We are in the grips of a mass extinction. There have been mass extinctions throughout evolutionary history, what makes this one different is that we’re the ones causing it. A recent review paper from GEE’s Dr Ben Collen discusses the current loss of biodiversity and suggests that our main concerns are species and population declines, […]

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Defaunation in the Anthropocene
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Evolving Endemism in East Africa’s Sky Islands

Fri, 08 Aug 2014 14:16:32 +0000

The World’s biodiversity is not evenly distributed. Some regions are hot spots for species richness, and biologists have been trying better to understand why these regions are special and what drives evolution and diversification. A recent paper by GEE’s Dr Julia Day and recent PhD graduate Dr Siobhan Cox, investigated the diversification of White-Eye Birds […]

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Mitochondria and the great gender divide - GEE's Profs Andrew Pomiankowski, Rob Seymour and Dr Nick Lane and Zena Hadjivasiliou publish paper in Proceedings of the Royal Society B

13 December 2011

8 December 2011

Eukaryotic cells

Why are there two sexes? It’s a question that has long perplexed generations of scientists, but researchers from UCL have come up with a radical new answer: mitochondria.

Using a new mathematical model, the team led by Dr Nick Lane and colleagues from the UCL CoMPLEX, and the Research Department of Genetics, Evolution and Environment showed that inheriting mitochondria from only one parent – in effect, the ‘female’ – improves fitness by optimizing the interactions between the two genomes. The paper is published today in Proceedings of the Royal Society B.

Dr Lane said: “The difference between the sexes boils down to the need to keep fit when energy demands are high”.

Descended from free-living bacteria, mitochondria were swallowed whole by another cell between one and a half to two billion years ago. But despite being engulfed, these tiny power packs have retained their own tiny genome, encoding just a handful of proteins, all of which are necessary for generating energy in the cell. 

The strangest thing about this odd arrangement is that cell respiration relies on proteins encoded by two genomes, the tiny mitochondrial genome and the nucleus, where most DNA is stored. For respiration to work properly, the two genomes must work together to encode proteins that interact with nanoscopic precision. 

"This difference seems to be the deepest evolutionary difference between the two sexes" - Zena Hadjivasiliou

Zena Hadjivasiliou, a PhD student in CoMPLEX and first author of the paper, said: “A clue to the answer was found in simple single celled organisms called protists. These tiny creatures normally have two sexes, despite the fact that it is impossible to tell them apart even with an electron microscope. 

“The only real difference between these ‘sexes’ relates to mitochondria, the tiny power packs found in all complex cells. In simple protists, one sex passes on mitochondria, the other does not,” added Hadjivasiliou. 

While the model shows that two sexes are only borderline necessary in simple cells like protists, but by the time large, energetically demanding organisms had evolved, two sexes made a big difference to maintaining fitness. 

Hadjivasiliou said: “This difference seems to be the deepest evolutionary difference between the two sexes. As a result all the gender wars throughout nature ultimately stand on this pinhead.”

Image: Altmann's Bioblasts - The four seasons (Credit: Odra Noel)

Links

Nick Lane
Energy revolution key to complex life
UCL’s Nick Lane wins the 2010 Royal Society Prize for Science Books
Research in Proceedings of the Royal Society B
UCL CoMPLEX
Research Department of Genetics, Evolution and Environment

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