LifeLine

Life on Earth is breathtakingly diverse, from the tiniest bacteria to human beings. But this diversity didn’t happen overnight. It’s a result of a long and complex process known as evolution, the gradual change of life over time. 

Evolution is change: genetic change in populations across generations. It explains how all living things are related and how they have adapted to survive in different environments. This change occurs through generational time. It should be passed down and across multiple generations. Evolution is caused due to a change in DNA, otherwise, a trait cannot be passed down. 

Evidence of evolution

• Change in the anatomical feature/anatomy of a living being (physical features)
• Fossils – breakdown/breakthrough evidence
• Biochemical change in the structure species homo-sapiens of DNA

Evidence for evolution comes from many sources, including the study of fossils, artificial selection in the production of domesticated breeds, from studies of the comparative anatomy of groups of related organisms, and from the geographical distribution of species.

Fossils allow us to understand and know about events and processes that occurred many years ago and over a long period of time. Fossilization is an extremely rare, chance event. Predators, scavengers and bacterial action normally break down dead plant and animal structures before they can be fossilized. Of the relatively few fossils formed, most remain buried or, if they do become exposed, are overlooked or accidentally destroyed.

Despite being such a rare event, numerous fossils have been found – and more continue to be discovered all the time. If the fossil, or the rock that surrounds it, can be accurately dated (using radiometric dating techniques, which measure naturally occurring radioactive substances such as carbon-1- in relation to the amount of carbon-12), we have good evidence of the history of life

Theory of natural selection

Organisms that are more adapted to their environment are more likely to survive and pass on the genes that aided their success. This process causes species to change and diverge over time. Nature will select something to propagate so that the species can be the fittest to survive

Variation happens in DNA, during meiosis. Any variation that is advantageous/beneficial to the species and helps its survival in the environment will be passed down through generations. 

After carrying out extensive research, Darwin developed his ‘theory of evolution by natural selection:

• Individuals within a population show variation.
• Populations produce more offspring than needed to replace them – large numbers of offspring lead to overpopulation. The population size remains constant, however.
• Resources such as food are limited. There is competition between individuals for food, mates, etc. There is a ‘struggle for existence’ and many individuals die.
• Individuals best adapted to their environment survive.
• These successful organisms are more likely to breed and pass on their genes to the next generation. This continues over many generations.

Example of Natural Selection

During the Industrial Revolution in Britain, in the early part of the nineteenth century, air pollution by gasses (such as sulfur dioxide) and soot was distributed over the industrial towns, cities and surrounding countryside. Here, lichens and mosses on tree trunks were killed off and these surfaces were blackened. The numbers of dark varieties of some 80 species of moth increased in these habitats in this period. This rise in proportion of darkened forms is known as industrial melanism.

The dark-coloured (melanic) form of the peppered moth Biston betularia tended to increase in these industrialized areas, but their numbers were low in unpolluted countryside, where pale, speckled forms of moths were far more common. The melanic form was effectively camouflaged from predation by insectivorous birds in sooty areas, and became the dominant species.

Human Evolution

Humans are no exception. We share about 98.8% of our DNA with chimpanzees, our closest living relatives. Fossil evidence shows that modern humans, Homo sapiens, evolved around 300,000 years ago. Along the way, our ancestors developed bigger brains, the ability to walk upright, and complex languages and cultures.

Today

One common misconception is that evolution is over. But it’s not. Bacteria evolve resistance to antibiotics. Insects evolve resistance to pesticides. Animals adapt to changing climates. Even humans continue to evolve. But the process is subtle and slow.

Understanding evolution isn’t just about the past. It helps us understand disease, protect endangered species, and develop better crops. It teaches us that life is dynamic, interconnected, and always adapting. It connects every living thing, past and present. And though we may not know exactly what the future holds, one thing is certain: life will keep evolving.