Archive for Evolution
www.bbc.co.uk 10th august 2011
A new report published in the Current Biology has found that a new hybrid of mice holds a higher than normal resistance to pest control poisons. The report studied the rapid evolution of German and Spanish mice when they mated with Algerian members of the species. The result was that the gene combination made the offspring increasingly resistant to the drug warfarin, which is an anti-coagulant used in pesticides. The research was led by Professor Michael Kohn from Rice University in Houston, Texas, who said: ”Our study is so special because it involves hybridisation between two species of mouse that are 1.5-3 million years removed from each other. Most of the offspring… do not reproduce, they are sterile – but there is a small window, which remains open for genes to be moved from one species to the other, and that’s through a few fertile females – so there is a chance to leak genes from one species to another.” Although the hybrid mice may not look any different from normal household European mice, they have in fact the ability ‘to survive the strongest chemicals in the pest control armoury.’
www.nationalgeographic.com 20th October 2010
Researchers at the University of Bristol, have made some headway into finding out why big cats have the beautiful yet bizarre patterning on their fur. A study of 35 different feline species led the team to suggest that the patterns are,in fact, evolved from camouflage. The data was fed into a ‘mathematical model of pattern development’. The results showed that those big cats that lived in areas of low-light levels such as jungle are more likely to be patterned, ‘especially with particularly irregular or complex patterns.’ Although a link between environment and patterns was established, there were anomlaies. The cheetah, for example, prefers open landscapes yet still have mottled coats. Similarly, the bay cat and the flat-headed cat have plain coats yet live in closed environments. The study also revealed why there are black leopards yet there are no black cheetahs. Leopards, under different names, live in a wide variety of habitats whereas cheetahs do not. “Having several environmental niches that different individuals of the species can exploit allows atypical colors and patterns to become stable within a population,” explained the report by Allen, Cuthill, Scott-Samuel and Baddeley of Bristol’s School of Experimental Psychology, published in the Proceedings of the Royal Society. No explanation has yet been given as to why tigers have their particularly effective form of camouflage.
Sources: news.nationalgeographic.co.uk 1st September 2010
Geographically separate lizards of the same species are giving birth in different ways. In the lower lying coastal lands of New South Wales, Australia, the Yellow-Bellied Three-Toed Skink lays eggs to reproduce but in the higher mountain lands further inland the same species of Skink gives birth to live young. Only two other reptile species in the world are known to use both types of reproduction. However, the transition from one type to the other poses some difficult questions for biologists. Live young require nutrients inside the womb via a complicated system involving the placenta. Young born in eggs receive their nutrients through the yolk of the egg as well as an important source of calcium from the shell. Reptiles in the process of evolving from the latter type of reproduction to the former face a potential lack of nutrients as the placenta is not yet formed and the egg is diminished. To combat this problem it seems that female Yellow-Bellied Skinks secrete calcium from their uterus walls which is then absorbed by the embryo. James Stewart, a biologist at East Tennessee State University, claims that this method represents “the early stages of the evolution of a placenta in reptiles.”
There are reptiles and fish who use both reproductive types at once. A thinner egg forms within the mother but the young hatches while still within the womb and is born live. The mother keeps the remnants of the egg within her.