Final answer:
Hosts respond to parasitic invasions by activating their immune system, behaviorally avoiding parasites, and developing adaptive defenses. They may produce antibodies, groom themselves, or undergo physiological changes to deter parasites.
Step-by-step explanation:
Host responses to parasitic invasions can vary depending on the specific host-parasite interaction. Some host responses include the activation of the immune system to eliminate the parasite, behavioral avoidance of contact with the parasite, and the development of adaptive defenses to regulate parasite numbers and minimize their negative effects. For example, hosts may produce antibodies to target and neutralize parasites, or they may groom themselves or exhibit grooming behaviors to physically remove parasites. Additionally, hosts may undergo physiological changes, such as increasing body temperature or releasing chemicals to deter parasites. Overall, host responses to parasitic invasions aim to prevent or minimize infections and counteract the negative effects of parasites on the host population.