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12/02/24 06:59 AM IST

Darwin Day

In News
  • February 12 is globally celebrated as Darwin Day to mark the birthday of naturalist Charles Darwin (12 February 1809 – 19 April 1882).
Genetic variations
  • Darwin and Wallace proposed that genetic diversity in a population helps its adaptation to a constantly changing environment. This is a continuous process.
  • For example, suppose a small fraction of a population carries genetic variants that make them tolerate higher temperatures.
  • While such variants may have little advantage if organisms live in optimal ambient temperature conditions, individuals carrying those variations can survive better and reproduce at a higher frequency if the environmental temperature increases.
  • This results in an increased proportion of individuals carrying heat-resistant genetic variations in subsequent generations.
  • The term “fitness” is used to explain changes in the relative proportion of genetic variations, in a population across generations.
  • This is the process that Darwin and Wallace termed as “natural selection”.
  • The occurrence of specific genetic variations in a population that helps its adaptation to a new environment is only a chance event. But the greater the genetic diversity in a population, the higher the chances that at least a few individuals will adapt to the new environment.
  • Sometimes, populations split and get separated for several reasons.
  • For example, a group of individuals physically move away from the main population and remain isolated.
  • While the same evolutionary mechanisms operate in both populations, without intermixing, accumulated genetic variations over many generations could result in their evolution into two morphologically/ behaviorally distinct groups or species.
Process of evolution
  • This process of evolution by divergence has been operating for nearly 3.5 billion years across the Earth, resulting in the spectacular biodiversity that we see – both in fossil records (such as of dinosaurs) and in today’s living world.
  • A better understanding of evolution has helped scientists realise that fundamental mechanisms of life are similar among all known living forms.
  • As a first step, at the beginning of the 20th century, scientists proved that patterns of genetic inheritance were similar across all organisms studied – from micro-organisms to humans.
  • Within the next 50 years, scientists discovered DNA, its structure, how the genetic information is coded in DNA, and the mechanisms by which it is decoded for various functions in a living cell.
  • The genetic information of an organism is copied and transferred to the next generation at a very high degree of fidelity.
  • So, all living organisms or those that ever lived (earliest known life forms that resemble current forms are as old as 3.75 billion years) on Earth have identical chemistry of life.
DNA Copying mechanism
  • Scientists also discovered that the DNA copying mechanism, while highly accurate, is not 100% error-proof.
  • This is the primary source of genetic variations helping populations to adapt, survive and perpetuate in diverse and changing environmental contexts.
  • This process also makes every individual in a population (except monozygotic twins) genetically distinct from the other members.
  • Chimpanzees and humans have diverged from a common ancestral great ape species (now extinct). Several human species evolved and became extinct except us, the modern humans ‘Homo sapiens’.
  • Interestingly, multiple human species co-existed on Earth simultaneously, often in the same geographical area.
  • Humans have learnt to live on frozen lands, deserts, marshy lands, rain forests, and many other extreme conditions.
  • They have lived and survived ice ages, famines and floods and have passed on their genes and learnings to us.
  • This means virtually every human society, lived and living has contributed to our knowledge and skills of today.
  • One cannot quantify who contributed more or less by using the yardsticks of today’s utility.
  • This understanding should make us respect diversity in human genetics, physiology, languages, histories and cultures.
Source- Indian Express

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