What is Biological Evolution

Traditional Evolution Illustration

The word “revolution” means a rapid change, and the word “evolution” means a slow change. Slow changes in the natural world are described as geological evolution (when mountains change), chemical evolution (when elements slowly change), astronomical evolution (when stars and planets slowly change), and biological evolution (when life forms slowly change).

Biological evolution is a biological process that happens not to individuals but to groups (or populations) of living things. The time it takes for a living population to evolve depends on the reproduction time of the organism. Some microbes (one celled organisms like bacteria) take only about 30 minutes to double in number. In one week these bacteria will have 336 generations (which is the equivalent of 84 centuries for humans). So populations of microbes can evolve in about a week’s time. Other organisms may take thousands, even millions of years.

Biological evolution takes place at the genetic level (the level of DNA molecules). It is the DNA in our cells that direct our bodies how to grow and develop. They are the instruction manuals for our body. When copying the DNA to make more cells, sometimes nature makes mistakes called “mutations.” Most of these mistakes are harmful to the organism, some don’t seem to make any difference, while others may help the organism survive. When these mutations occur in the germ or sex cells (the sperm or egg cells) they are passed on to future generations of the organism.

These mutations together with the genetic mix happening through sexual reproduction when the genes from the male are united with the genes from the female provide the variation in offspring characteristics needed for evolution to occur. Organisms produce lots of offspring, far more than can survive because of limited food and lots of predators. Because of the variation in offspring some have characteristics or traits which give them a better chance at survival.