Final answer:
New drug-resistant malaria strains in red blood cells exemplify natural selection, where resistant Plasmodium parasites survive and reproduce in the presence of anti-malarial drugs.
Step-by-step explanation:
The phenomenon of new strains of malaria-causing parasites in red blood cells that are resistant to traditional drugs can be understood as an example of natural selection. Malaria, caused by Plasmodium species such as Plasmodium falciparum, is transmitted by the bite of infected female Anopheles mosquitoes. However, over time, some parasites have developed mutations that confer resistance to the anti-malarial drugs used to treat the infection. This drug resistance means that when drugs are used to treat malaria, parasites without the resistance are killed, while the resistant ones survive and reproduce. As a result, the frequency of drug-resistant parasites increases in the population. This is natural selection in action, as the organisms better adapted to the environment, in this case, a drug-treated human host, survive to pass on their genes while the less adapted perish.