Final answer:
Genetic similarity between humans and other species is high due to shared ancestry, but allelic similarity is low due to unique genetic variations developed through evolutionary processes.
Step-by-step explanation:
Genetic similarity between humans and other species is very high because all living organisms share a common ancestry. This means that they have similar genetic codes and genes that perform similar functions. However, allelic similarity is low because each species has evolved unique variations of genes and alleles over time through processes such as speciation events, genetic drift, and natural selection.
For example, let's consider convergent evolution. Convergent evolution occurs when unrelated species independently evolve similar traits in response to similar environmental pressures. Due to this convergent evolution, species that are not closely related can develop similar traits and behaviors, but their genetic makeup and specific alleles can still be different.
In summary, genetic similarity between humans and other species is high because of our shared ancestry, but allelic similarity is low due to the unique adaptations that species have developed through evolutionary processes such as divergent evolution, convergent evolution, speciation events, and genetic drift.