How Are Plant-like Protists Useful To The Environment?

Protists

Environmental of Protists

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Learning Objectives

By the terminate of this section, you will be able to:

• Depict the role that protists play in the ecosystem
• Describe important pathogenic species of protists

Protists function in various ecological niches. Whereas some protist species are essential components of the food chain and generators of biomass, others role in the decomposition of organic materials. Yet other protists are dangerous human pathogens or causative agents of devastating plant diseases.

Primary Producers/Food Sources

Protists are essential sources of nutrition for many other organisms. In some cases, as in plankton, protists are consumed directly. Alternatively, photosynthetic protists serve as producers of nutrition for other organisms. For instance, photosynthetic dinoflagellates called zooxanthellae use sunlight to fix inorganic carbon. In this symbiotic relationship, these protists provide nutrients for coral polyps ([link]) that house them, giving corals a boost of energy to secrete a calcium carbonate skeleton. In plow, the corals provide the protist with a protected environment and the compounds needed for photosynthesis. This type of symbiotic human relationship is important in nutrient-poor environments. Without dinoflagellate symbionts, corals lose algal pigments in a process chosen coral bleaching, and they eventually dice. This explains why reef-building corals practise non reside in waters deeper than 20 meters: insufficient light reaches those depths for dinoflagellates to photosynthesize.

Coral polyps obtain nutrition through a symbiotic human relationship with dinoflagellates.

The protists themselves and their products of photosynthesis are essential—directly or indirectly—to the survival of organisms ranging from bacteria to mammals ([link]). As primary producers, protists feed a large proportion of the earth's aquatic species. (On land, terrestrial plants serve every bit main producers.) In fact, approximately ane-quarter of the globe's photosynthesis is conducted by protists, particularly dinoflagellates, diatoms, and multicellular algae.

Virtually all aquatic organisms depend directly or indirectly on protists for food. (credit "mollusks": modification of work by Craig Stihler, USFWS; credit "crab": modification of work by David Berkowitz; credit "dolphin": modification of work past Mike Baird; credit "fish": modification of work by Tim Sheerman-Chase; credit "penguin": modification of piece of work past Aaron Logan)

Protists practise non create food sources but for sea-abode organisms. For case, certain anaerobic parabasalid species exist in the digestive tracts of termites and forest-eating cockroaches, where they contribute an essential step in the digestion of cellulose ingested by these insects every bit they bore through forest.

Human Pathogens

A pathogen is anything that causes disease. Parasites live in or on an organism and harm the organism. A significant number of protists are pathogenic parasites that must infect other organisms to survive and propagate. Protist parasites include the causative agents of malaria, African sleeping sickness, and waterborne gastroenteritis in humans. Other protist pathogens prey on plants, effecting massive destruction of nutrient crops.

Plasmodium Species

Members of the genus Plasmodium must colonize both a mosquito and a vertebrate to complete their life cycle. In vertebrates, the parasite develops in liver cells and goes on to infect red blood cells, bursting from and destroying the blood cells with each asexual replication cycle ([link]). Of the four Plasmodium species known to infect humans, P. falciparum accounts for 50 pct of all malaria cases and is the main crusade of illness-related fatalities in tropical regions of the world. In 2010, it was estimated that malaria caused between one-half and one 1000000 deaths, mostly in African children. During the course of malaria, P. falciparum can infect and destroy more than ane-half of a human'due south circulating blood cells, leading to severe anemia. In response to waste products released as the parasites burst from infected blood cells, the host immune system mounts a massive inflammatory response with episodes of delirium-inducing fever as parasites lyse crimson blood cells, spilling parasite waste matter into the bloodstream. P. falciparum is transmitted to humans by the African malaria mosquito, Anopheles gambiae. Techniques to kill, sterilize, or avert exposure to this highly aggressive mosquito species are crucial to malaria command.

Red claret cells are shown to be infected with P. falciparum, the causative agent of malaria. In this lite microscopic prototype taken using a 100× oil immersion lens, the ring-shaped P. falciparum stains purple. (credit: modification of work by Michael Zahniser; scale-bar data from Matt Russell)

Link to Learning

This movie depicts the pathogenesis of Plasmodium falciparum, the causative agent of malaria.

Trypanosomes

Trypanosoma brucei, the parasite that is responsible for African sleeping sickness, confounds the man immune arrangement by changing its thick layer of surface glycoproteins with each infectious cycle ([link]). The glycoproteins are identified by the immune system as strange antigens, and a specific antibody defence force is mounted against the parasite. Withal, T. brucei has thousands of possible antigens, and with each subsequent generation, the protist switches to a glycoprotein blanket with a dissimilar molecular construction. In this way, T. brucei is capable of replicating continuously without the allowed arrangement ever succeeding in clearing the parasite. Without treatment, T. brucei attacks red blood cells, causing the patient to lapse into a coma and somewhen die. During epidemic periods, mortality from the disease tin can be high. Greater surveillance and control measures atomic number 82 to a reduction in reported cases; some of the lowest numbers reported in 50 years (fewer than 10,000 cases in all of sub-Saharan Africa) have happened since 2009.

Link to Learning

This picture discusses the pathogenesis of Trypanosoma brucei, the causative agent of African sleeping sickness.

In Latin America, some other species, T. cruzi, is responsible for Chagas disease. T. cruzi infections are mainly caused by a claret-sucking bug. The parasite inhabits middle and digestive system tissues in the chronic phase of infection, leading to malnutrition and heart failure due to abnormal heart rhythms. An estimated 10 1000000 people are infected with Chagas disease, and it caused ten,000 deaths in 2008.

Trypanosomes are shown amidst blood-red claret cells. (credit: modification of work by Dr. Myron Yard. Shultz; scale-bar data from Matt Russell)

Institute Parasites

Protist parasites of terrestrial plants include agents that destroy food crops. The oomycete Plasmopara viticola parasitizes grape plants, causing a affliction called downy mildew ([link]). Grape plants infected with P. viticola appear stunted and have discolored, withered leaves. The spread of featherlike mildew well-nigh complanate the French vino industry in the nineteenth century.

Both downy and powdery mildews on this grape leaf are caused by an infection of P. viticola. (credit: modification of work past USDA)

Phytophthora infestans is an oomycete responsible for potato tardily blight, which causes murphy stalks and stems to decay into black slime ([link]). Widespread potato blight caused past P. infestans precipitated the well-known Irish gaelic murphy famine in the nineteenth century that claimed the lives of approximately ane million people and led to the emigration of at least 1 million more from Ireland. Tardily bane continues to plague potato crops in certain parts of the U.s.a. and Russian federation, wiping out every bit much as 70 percent of crops when no pesticides are applied.

These unappetizing remnants outcome from an infection with P. infestans, the causative agent of white potato tardily blight. (credit: USDA)

Agents of Decomposition

The fungus-like protist saprobes are specialized to absorb nutrients from nonliving organic matter, such equally dead organisms or their wastes. For instance, many types of oomycetes grow on dead animals or algae. Saprobic protists take the essential function of returning inorganic nutrients to the soil and water. This process allows for new establish growth, which in turn generates sustenance for other organisms along the food concatenation. Indeed, without saprobe species, such as protists, fungi, and bacteria, life would cease to exist every bit all organic carbon became "tied up" in expressionless organisms.

Section Summary

Protists function at several levels of the ecological food web: every bit primary producers, as direct nutrient sources, and as decomposers. In addition, many protists are parasites of plants and animals that tin cause deadly human being diseases or destroy valuable crops.

Review Questions

An example of carbon fixation is _____________.

1. photosynthesis
2. decomposition
3. phagocytosis
4. parasitism

A

Which parasitic protist evades the host immune system by altering its surface proteins with each generation?

1. Paramecium caudatum
2. Trypanosoma brucei
3. Plasmodium falciparum
4. Phytophthora infestans

B

Free Response

How does killing Anopheles mosquitoes affect the Plasmodium protists?

Plasmodium parasites infect humans and crusade malaria. Still, they must complete part of their life cycle inside Anopheles mosquitoes, and they can only infect humans via the seize with teeth 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 atomic number 82 to death?

The trypanosomes that cause this disease are capable of expressing a glycoprotein coat with a dissimilar molecular structure with each generation. Because the immune system must answer to specific antigens to heighten a meaningful defence force, the changing nature of trypanosome antigens prevents the immune system from e'er immigration this infection. Massive trypanosome infection eventually leads to host organ failure and death.

How Are Plant-like Protists Useful To The Environment?,

Source: http://pressbooks-dev.oer.hawaii.edu/biology/chapter/ecology-of-protists/

Posted by: gasparddienteor.blogspot.com

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