What is meant by genetic polymorphism within a population?

Genetic polymorphism refers to the occurrence of two or more distinct forms or alleles of a gene within a population. It is a key concept in evolutionary biology as it signifies the genetic diversity present among individuals in a species. This diversity can manifest in various ways, such as variations in traits, allelic differences, or the presence of multiple phenotypes that arise from different alleles at a specific locus.

In a population exhibiting genetic polymorphism, these different gene forms can lead to variations in characteristics that may affect an organism's adaptability, survivability, and reproductive success. This concept is crucial because it can drive natural selection and contribute to the evolutionary processes within that population.

The other options do not accurately define genetic polymorphism. The presence of different species in the same habitat refers to biodiversity rather than variations within a single species' genes. Variations in physical traits due to environmental influences are more about phenotypic plasticity rather than genetic diversity, while a lack of genetic diversity contradicts the notion of genetic polymorphism.