Evolution is the process by which life changes through its genetic inheritance: descent with modification. Evolution is a fundamental concept of biology and it includes the principles that species change over time, that different species share common ancestors, and that the changes and adaptations are generally small and gradual.
It is a fact that evolution occurs, and there are theories as to the causes of evolution. These theories include natural selection as the mechanism for evolution, independently proposed by Charles Darwin and Alfred Russell Wallace.
Natural selection operates though natural forces (such as predators, food availability, disease, rainfall, temperature etc) acting on the biological variation occurring within species. This variation is produced by mutations in the genes of organisms. Genes carry the blueprints for the physical characteristics (or traits) of individuals. If a particular trait is advantageous to the survival of certain individuals within a species – such as a particular colour giving a competitive advantage over other colour forms in predator avoidance – this trait will improve those individuals’ chances of successfully reproducing and thus passing on the trait to their offspring.
Over time, an advantageous trait will become more common in populations, provided that the natural selective pressures remain the same. Similarly, traits that reduce the survival and reproductive success of a species will become rarer. If the selective pressures change – such as particular environmental changes, like increases or decreases in the availability of water –other traits in a population may be selected for instead. In this way, species continue to evolve in parallel with their environments.
As the environment changes more and more, a species must become adapted to the local conditions in order to survive and reproduce. The alternative is ‘extinction’. The individuals of this adapted species are different – sometimes very different - to their ancestors, and scientists recognise them as new species, distinct from the original (or ‘parent’) species. In other instances, populations of a single species may become isolated from each other by barriers, like mountain ranges, seas or arid zones. Each of these populations may face different environmental conditions and the two populations will then slowly drift apart, each adapting to their local environment, and eventually evolve into two new distinct species incapable of reproducing with each other.
Species that have high genetic variability within their populations are theoretically capable of adapting to changing environments more easily than species with low genetic variability. The variation gives them survival options in rapidly changing environments. Maintaining extensive natural populations of species is therefore advantageous to their probabilities for survival. Keeping high levels of natural genetic variation is vital to conservation efforts. Reducing the sizes and geographical ranges of species through environmental degradation and over-exploitation is therefore a recipe for their impending extinction.
Many research projects undertaken by Queensland Museum scientists include the study of evolution of particular groups of animals, using both traditional and molecular techniques. These studies help us to explain the history of the Queensland fauna, and their relationships with close and more distant neighbours.
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