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Skip to main content. Search for free courses, interactives, videos and more! Free learning from The Open University. Featured content. Mosquitos suck blood containing the protists from an infected person. They pass the protist, to other people they suck blood from. The mosquitos do not become ill and are called ' vectors ' because they transmit the disease.
Protists function at several levels of the ecological food web: as primary producers, as direct food sources, and as decomposers. In addition, many protists are parasites of plants and animals and can cause deadly human diseases or destroy valuable crops. Which parasitic protist evades the host immune system by altering its surface proteins with each generation?
Which of the following is not a way that protists contribute to the food web? How does killing Anopheles mosquitoes affect the Plasmodium protists? Plasmodium parasites infect humans and cause malaria. However, they must complete part of their life cycle within Anopheles mosquitoes, and they can only infect humans via the bite wound of a mosquito. If the mosquito population is decreased, then fewer Plasmodium would be able to develop and infect humans, thereby reducing the incidence of human infections with this parasite.
Without treatment, why does African sleeping sickness invariably lead to death? The trypanosomes that cause this disease are capable of expressing a glycoprotein coat with a different molecular structure with each generation. Because the immune system must respond to specific antigens to raise a meaningful defense, the changing nature of trypanosome antigens prevents the immune system from ever clearing this infection. Massive trypanosome infection eventually leads to host organ failure and death.
Describe how increasing stress to the ocean would affect a food chain containing zooxanthellae, corals, parrotfish, and sharks. Ocean stresses, such as rising temperatures or increasing levels of pollution, cause corals to expel their zooxanthellae symbionts. This leads to coral bleaching, and death if no new zoocanthellae colonize the corals.
The dying corals will decrease the food source available to parrotfish, so the parrotfish population will decline.
With fewer prey animals available, the shark population in the area will also decline. Skip to content Protists. Learning Objectives By the end of this section, you will be able to do the following: Describe the role that protists play in the ecosystem Describe important pathogenic species of protists. Coral with symbiotic dinoflagellates.
Coral polyps obtain nutrition through a symbiotic relationship with dinoflagellates. Protists contribute to the food chain. Virtually all aquatic organisms depend directly or indirectly on protists for food. Human Pathogens As we have seen, a pathogen is anything that causes disease.
Malaria parasite. Red blood cells are shown to be infected with P. Link to Learning. Autecology cellular organelles and secretions, encystment and dispersal abilities , environmental conditions physiological tolerances and interaction with other organisms , and evolutionary history contribute to protist biogeography, which manifests ecological and historical aspects.
Ecological biogeography is seen in the influence of geochemistry on the distribution of fresh-water phytoflagellates and algae, and of moisture and vegetation type on soil-litter protists.
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