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Evolving Change

      Survival Of The Fittest     

The earth’s climate is changing. You read about that everywhere — in text books, sci-fi novels, magazines and newspapers. But did you know that some animals and plants are also ‘changing’ themselves to keep pace with climate? And most interestingly, human beings, too, are adapting, say scientists. But we are way behind….

      What’s Climate Change?     

The earth receives short wave radiation from the sun, onethird of which is absorbed by the atmosphere, oceans, ice, land and living organisms. The energy absorbed from solar radiation is balanced, by outgoing radiation from the earth. But long-wave emitted by the warm surface of the earth is partially absorbed by trace gases in the atmosphere called greenhouse gases (GHGs). The main GHGs are water vapour, carbon dioxide (CO2) and methane (CH4). In the absence of these gases, the earth would have been 33oC lower in temperature than today. In the late 1980s, scientists began to say that the earth’s energy flux was no longer in balance. Earth was getting warmer and affecting the climate. That the climate was changing.

      And what happens then...     

The dire consequences are already apparent. Polar ice caps and glaciers are melting down, leading to a rise in the sea level, which in turn will submerge coastal areas and islands forever. Even our ecosystems are changing, as the delicate balance between different species is disrupted. And the dreadful list goes on. The outcome will be simply apocalyptic for every living creature in this planet!

The rate of climate change is the greatest determinant of the impact on biological diversity. Numerous studies have shown how seasonal growth patterns of plants and animals are altering with rising temperatures. A change in climate can also speed up the course of evolution, proving Darwin’s theory of ‘Survival of the fittest’.

Climate change triggers extinction as well as speciation. Animals have three mechanisms for coping with it: they can either use physiological flexibility or evolve new adaptations or migrate to better sites. Climate change causes extinction by altering the type and availability of ecological niches (potential homes for animals and plants), resulting in conditions that are unsuitable for previously thriving species. When animals can’t move to habitats that provide favourable climate, climate change leads to evolutionary changes or extinction.

       Nature takes over     

Evolution has already begun to cope with the rapidly changing global climate. Many species of flora and fauna have either evolved new characteristics to adapt to the change or they are migrating to cooler regions. Here are a few examples:

Several orchids and ferns in Britain are flourishing in the north and west, while other species are retreating to cooler conditions on high land and mountainsides. Some of them are Bee orchid (Ophrys apifera), Pyramidal orchid (Anacamptis pyramidalis), Hart’s Tongue fern (Phyllitis scolopendrium) and Prickly lettuce (Lactuca serriola), while Lesser Butterfly orchid (Platanthera bifolia), Goldenrod (Solidago virgaurea), Mountain pansy (Viola lutea), Lousewort (Pedicularis sylvatica) are dying out.

The Hawaiian branching coral Montipora capitata recovered from bleaching caused by global warming by increasing its intake of tiny plankton. It is a path breaking discovery, as scientists predict that global warming may destroy 60 percent of reefs worldwide in the next few decades.

In Antarctica, penguins are indicating evolution resulting from climate change. Though there are no notable changes to the appearance or behaviour of the birds, there are small-scale evolutionary changes to the genetic sequence of the penguins’ DNA.

Even human genes are evolving in response to climate change. Human genes involved in metabolism, skin pigmentation, brain function and reproduction have evolved according to a new study of natural selection in the human genome.

      Science lends a helping hand     

Scientists and researchers are also doing their bit to find ways to cope with changing climate.Scientists at Emory University in Atlanta say they might have found a way to remove more carbon dioxide from the atmosphere using a mutant enzyme that can enable plants to use and convert carbon dioxide more quickly, effectively taking more of that gas from the atmosphere.

Climate change may reachthe point of no return — if we do not take drastic steps now.. But Nature is finding its own way out. The healing process has already begun. While some species will lose the battle for survival, some species will adapt themselves, evolve and survive. But, what will happen to humans? Will “the cause” of this catastrophe bear its effects? Or it will adapt or evolve into something new? Or just become extinct?

DNA sequencing of many fossil bones provide us a glimpse into genetic changes that have occurred over time. Other tools include molecular clocks that determine when species diverged using DNA sequence differences and Morphometrics that measures changes in physical features. Glaciation or Global Cooling was probably a major factor in the mass extinctions in the late Ordovician era, the late Devonian, the end Permian era, and it might also have been a factor in the extinction event at the end of the Cambrian periods. Another type of climate change — an increase in rainfall — may have caused another extinction in the late Triassic


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Survival of the fittest