Answer:
Cline
Step-by-step explanation:
Cline refers to a noticeable and gradual change of some phenotypic traits over a geographical region. The phenotypic traits such as body size, coloration, etc. exhibit continuous variation or gradient over a geographical region.
Clines result from geographical variations within a species. Clines are usually related to the gradient of abiotic factors such as temperature, pressure, light, altitude. Gene flow between the populations present along the gradient of abiotic factors results in continuous variations in allele frequencies.