Reproducing is the way a species stays alive from generation to generation. The science of genetics explains how a species’ traits are passed on from parents to offspring. Reproduction and the passing on of traits are part of the theory of evolution. This theory explains the diversity of species you see around you—insects, plants, pets, and your friends and family—and how these species can change over time.
Have you ever been to an anthropology exhibit at a museum and seen pictures or models of cavemen? These early humans, scientifically called Homo erectus, may be ancestors of the modern day human, called Homo sapiens. Although there are striking similarities between Homo erectus and Homo sapiens, there are also distinct differences, particularly in skull shape. Scientists believe that over time, human characteristics changed. Physical appearance, mental capabilities, and emotional state of mind evolved in response to environmental changes. In this lesson, you will learn about evolution and its mechanisms.
Evolution and Change
If you have ever seen a caterpillar change into a butterfly or looked at old baby pictures of your parents, you know that all organisms change over time. The difference among evolution, metamorphosis, and simply growing up is genetics. Evolutionary changes are caused by new gene combinations or genetic mutations. This is not the case with metamorphosis or maturation. A butterfly has the same genes it had as a caterpillar, and your parents have the same genes they had as babies. Homo erectus, on the other hand, has different genes from Homo sapiens. Evolution is based on genetic inheritance. A change in the genotype of an organism is passed down from parent to offspring again and again. Over time, the genes in a population change and the phenotype of an organism is altered.
Imagine a population of black beetles. A mutation in the DNA of a single beetle causes it to have a green shell. The mutated beetle mates with another normal beetle and passes the color mutation to a few more beetles. These beetles then mate and create more green beetles. Over the course of several generations, the population of beetles changes and becomes predominately green in color. The population has evolved.
Evolution is usually associated with improvement. For example, an idea may evolve into a theory or an orderly crowd may devolve into an angry mob. Evolution results in organisms that have an improved ability to survive in their environment. These organisms are not necessarily better; they are simply better fit to their environment. This idea of “better” is one of the biggest misconceptions about evolution. Evolution is not a ladder in which organisms at the bottom are worse than organisms at the top. Simple sponges and jellyfish have evolved very little for millions of years because they are well-adapted to their environment. This does not make them any less of an organism than horses, which have evolved many times. This idea of evolution and survival of a species through time (due to adaptability to their environment) is called, natural selection, a fundamental mechanism of evolution.