Is this an example of necrosis or apoptosis? The cysts migrate with ingested food to the small intestine where they produce trophozoites. Copyright 10. Protozoa are found drifting in the oceans, seas, … In human, the trophozoites are the active form of the parasite which penetrate into cells, except erythrocytes (red blood cells). The single macronucleus in the cells then degenerates. MSBSHSE Class 8 Science Chapter 1 Textbook Exercise Questions Question 1: Use Whittaker method to classify bacteria, protozoa, fungi, algae, prokaryotic and eukaryotic microbes. Through sexual reproduction genetic materials are exchanged between two compatible partners. This might lead to bursting of the protozoal cell, unless excess water is actively expelled through contractile vacuoles. 5.49) without flagella or cilia. Here we have provided NCERT Exemplar Problems Solutions along with NCERT Exemplar Problems Class 8.. Their body lacks a periplast. Most Porotozoans reproduce asexually and sexually during their lifetime. The zygote is transformed into a thick-walled oocyst. The examples are: 1. The surface (pellicle) is covered by a large number of short cilia arranged in a precise order. Trypanosoma 3. They move to the salivary gland of the mosquito and can be injected into another person. They are traditionally looked upon as animals, because most protozoans are animal-like. The organisms are non-flagellated amoebae. The following points highlight the top nine examples of protozoa. Sexual reproduction of this organism also takes place by conjugation. Paramecium can reproduce asexually by means of transverse binary fission. Plagiarism Prevention 4. They reproduce by binary fission. The examples are: 1. [MSE (Chandigarh) 2005, 2007] Answer: Question 2. Examples: Rhizopoda, Sarcodina, amoeba, mycetozoa, etc. They DO NOT HAVE Chlorophyll. Sexual reproduction is well studied in another ciliate, Tetrahymena, and is described next. The nuclei divide and each daughter cell receives one copy of the macronucleus which divides amitotically and a copy of micronucleus which divides by regular mitosis. The cilia also help in collecting solid food particles into the mouth. Cryptosporidiosis, & more. Question from very important topics are covered by NCERT Exemplar Class 8.You also get idea about the type of questions and method to answer in your Class 8th examination. Microorganisms Class 8 Science Chapter 2 as per NCERT Book used in CBSE and other Schools. They also affect skin and additionally the mucous membrane. Carl Linnaeus is thought of as the father of modern taxonomy. Describe the nitrogen cycle with the help of a neat and labelled diagram. Trypanosoma gambiense. They possess proteolytic enzymes with the help of which they can penetrate the mucous layers producing lesions. 5.51: Biology, Microbiology, Eukaryotic Microorganisms, Protozoa, Examples of Protozoa. Termites, for example, have protozoans living in their body. Share Your PPT File. There is also a large characteristic sucking organ by which they attach to the intestinal wall. A visceral leishmaniasis, known as kala-azar is a serious type of infection, once widely prevalent in many parts of Asia including India, Africa and also Mediterranean countries. Trichonympha 4. At first, organisms were placed in groups based solely on what could be observed: appearance, behavior, and ecological niche. Answer: According to Robert Harding Whittaker, given below are the characteristic features of bacteria, protozoa, fungi, algae, prokaryotic and eukaryotic microbes: Typically, the cell is divided transversally, with the anterior half of the ciliate (the proter) forming one new organism, and the posterior half (the opisthe) forming another.However, other types of fission occur in some ciliate groups. The conventional scheme followed by Hyman (1940), Hickman (1961) and Storer (1965), etc. 2.3 Microorganisms and Us 2.4 Harmful Microorganisms 2.5 Food Preservation 2.6 Nitrogen Fixation 2.7 […] Read Or Download The Diagram Pictures Cell For FREE Cell Diagram at CROWDFUNDING.DEMO.AGRIYA.COM recognizes two subphyla on the basis of organs of locomotion and 5 classes as follows: 5.50. They are spread by the bite of a tsetse fly. Before sharing your knowledge on this site, please read the following pages: 1. After entering into the body with food or water, the cysts pass through the gastrointestinal tract until they reach the distal portions of the small intestine and the large intestine. Structure . All protozoans are eukaryotes and therefore possess a “true,” or membrane-bound, nucleus. One, known as T. brucei gambiense is common in Central Africa and the other T. brucei rhodesiense is restricted to east and south-east Africa. The pathogen exists in two forms in its life-cycle. Cysts are slightly smaller, oval and thick walled. Disclaimer Copyright, Share Your Knowledge The conjugation process of Tetrahymena is diagrammatically represented in Fig. In humans, the trophozoites develop from cysts or oocysts in the intestines and they penetrate the cells to spread throughout the body via blood stream. Leishmaniasis can be of different types caused by different species of Leishmania. L. brasiliensis causes disfiguration of nose, mouth and throat. Trichonympha campanula is a multi-flagellate symbiotic protozoan which inhabits the intestines of termites. In the invertebrate hosts trypanosomes are present as long slender flagellated organisms (Fig. How to avoid spreading of Micro-organisms has been discussed. The cytostome is inherited by one of the daughter cells. The macronucleus does not take any part in the conjugation process. Birds and rodents also are infected and the domestic cats may acquire the infection from them. It may be divided into several layers. Thus, each cell has one micronucleus and one macronucleus. Paramecium is a ciliate protozoan belonging to the Phylum Ciliophora. Protozoa. The organisms feed on bacteria and other microorganisms present in the habitat. E. histolytica is the causal agent of amoebiasis in humans. TOS4. It has hair-like projections, called cilia, which help it swim. Write 10 lines on the usefulness of microorganisms in our lives. NCERT Solutions for Class 8 Science Chapter 2 Microorganisms Friend and Foe Topics and Sub Topics in Class 8 Science Chapter 2 Microorganisms Friend and Foe: Section Name Topic Name 2 Microorganisms Friend and Foe 2.1 Microorganisms 2.2 Where do Microorganisms Live? Diseases like dysentery and malaria are caused by protozoa. ‘Protozoa’, in fact, means ‘the first animal’. It was Linnaeus who came up with the two-word descriptions of organisms: the genus and species names that all scientists are familiar with. Entamoeba 6. These particles are thought to be involved in synthesis of toxins which can kill other ciliates without the kappa factors, thereby eliminating competitors for food. Toxoplasmosis develops with fever, sore throat and enlargement of spleen, liver and lymph nodes. Cysts are highly resistant to anti- amoebic drugs and for that reason cause a chronic infection. They proliferate in the phagocytic leucocytes of the affected person. They are traditionally looked upon as animals, because most protozoans are animal-like. They also help to direct food and water into the oral groove of this organism. Tetrahymena. Report a Violation, Algae: Definition, Useful Algae and Eutrophication (with diagram), Essay on Biological Processes: As Self Purification of Natural Water System, Fungi: Definition and Types of Fungi (explained with diagram). Most species are free living, but all higher animals are infected with one or more species of protozoa. How to avoid spreading of Micro-organisms has been discussed. The pathogen grows in liver and spleen causing their enlargement. Question 2. Produces 3D character animation using its proprietary software and motion-capture methodology. Recently Viewed Questions of Class Biology. Goldfuss created Protozoa as a class containing what he believed to be the simplest animals. Their cysts can be found in the bleakest parts of the ecosphere. Paramecia are widespread in freshwater, brackish, and marine environments and are often very abundant in stagnant basins and ponds. Infection in humans is effected through the bite of a female anopheline mosquito carrying the sporozoites in its saliva. Leishmania includes several species of flagellated protozoa belonging to the class Zoomastigophora which cause different types of leishmaniasis in humans. After the exchange of nuclei has taken place, the two conjugating cells separate. The group of organisms known as 'protozoa' are defined by a few of their shared characteristics. The injected sporozoites are carried by the blood stream to the liver cells where each sporozoite produces up to 25,000 merozoites by schizogamy (multiple fission). L. tropica infects mostly skin causing a lesion. The others are either saprophytic or parasitic. Giardia 2. Privacy Policy 8. Answer: The substances that conduct electricity through them are called good conductors. Markdownish syntax for generating flowcharts, sequence diagrams, class diagrams, gantt charts and git graphs. 5.49. Trophozoites are transformed into cysts within host cells. The captured food particles are transferred to food-vacuoles. E. histolytica forms thick- walled cysts and the pathogen is transmitted in the form of cysts. In the phylogenetic classification (Table 5.5), they have been placed in the phylum Euglenozoa. NCERT Exemplar Class 8 Science is very important resource for students preparing for VIII Board Examination. Protozoans: Useful and Harmful Protozoans (explained with diagram)! Paramecia also contain the other eukaryotic cell organelles, like mitochondria, Golgi bodies, nucleus etc. One of these is invariably the female mosquitos belonging to the genus Anopheles and the other, vertebrate mammals including man. They grow generally in the small intestine of humans and other animals. The other cell has to form a new cytostome. The process begins when two cells of compatible mating types come in close contact and a cytoplasmic bridge is established between them. The Locomotory organelles are pseudopodia and flagella Nucleus is single or many … The protozoan Endamoeba histolytica causes amoebiasis (amoebic dysentery) in human beings, Giardia causes giardiasis (dysentery), while Plasmodium causes malaria. In the classification based on r-RNA homology, the genus is placed in the Archaezoa. It is a digenetic parasite. The liberated merozoites then infect the red-blood cells and develop into a ring-like structure which enlarges and eventually breaks up to produce numerous merozoites, as well as several gametocytes. Phylum protozoa General characteristics : • unicellular. Answer: ... NCERT Solutions for Class 8 … Protozoa that live in the blood or tissue of humans are transmitted to other humans by an arthropod vector (for example, through the bite of a mosquito or sand fly). Living Science 2019 Solutions for Class 8 Science Chapter 6 Combustion And Flame are provided here with simple step-by-step explanations. Explore their definition, types and important characteristics of algae. Protozoa species move on their own by one of the three types of locomotor organelles such as flagella, cilia, or pseudopodia. What is the significance of transpiration? Protozoa is a parasite and in humans, they are less than 50 μm in size. Paramecium 9. Answer: Question 9. Toxoplasma 8. Our mission is to provide an online platform to help students to share notes in Biology. When a tadpole turns into a frog, its tail shrinks and is reabsorbed. Learn more about it. All the cilia beat rhythmically to propel the organism in liquid medium. Question 1. The trophozoites measure about 14 μm in length and 7 μm in breadth and have eight flagella and two prominent nuclei (Fig. The cytostome consists of an oral aperture and a mouth cavity. Toxoplasma 8. Maharashtra State Bureau of Textbook Production and Curriculum Research General Science Book Class 8. Protozoa: Definition and Classification | Microbiology. 2. All questions and answers from the General Science Solutions Book of Class 8 Science Chapter 1 are provided here for you for free. Infection of African sleeping sickness in man is caused through bite of tsetse fly (Glossina palpalis). Giardia: The genus belongs to the Phylum Sarcomastigophora, Sub-phylum Mastigophora and class Zoomastigophora. Contractile vacuoles serve to expel excess of water from the cytoplasm, thus functioning as osmoregulatory organelles. Infection of Chagas’ disease is spread through bite of so-called “kissing bugs” (Triatoma). The diseases caused by different species are spread through bites of sand fly (Phlebotomus spp.). as well as eukaryotic ribosomes. Trypanosomes pass their life-cycle in two hosts, one a vertebrate mammal (specially human being) and an invertebrate host. 1. In the sand fly as well as in culture, the organisms are flagellated elongated structures (promastigote). Each cyst on germination produces several trophozoites. Answer: The substances that […] Image Guidelines 5. Get Revision notes of Class 8 th Science Chapter 2 Microorganisms : friend and foe to score good marks in your Exams. Algae in an informal term that describes a diverse group of eukaryotic, photosynthetic organisms. Diagram of protozoa 2 See answers Chetan007 Chetan007 This is the diagram of protozoa. Sexual union takes place in the intestine of mosquitoes resulting in the formation of a diploid zygote. The life-cycle of Plasmodium is depicted in Fig. Plasmodia reproduce both asexually and sexually. Trypanosomes are flagellated protozoa placed classically in the Zoomastigophora, but similarity of r-RNA homology with Euglenoids shows their affinity. Leishmania 5. Structure of Protozoa. Another feature of Paramecium is the presence of Kappa factors which are nucleic acid particles. Yeast: Origin, Reproduction, Life Cycle and Growth Requirements | Industrial Microbiology, How is Bread Made Step by Step? Motility. Some live in freshwater, some in salt water, and some in the soil. Maharashtra Board Class 8 Important Question Chapter wise Download at here. T. gondii is an intracellular parasite capable of existing in three forms — trophozoites, cysts and oocysts. 4. Most noteworthy, most of the diseases related to Protozoa happen inside the patient of AIDS (Acquired Immune Deficiency Syndrome). Protozoa reproduce by the method of binary fission or multiple fission. The food particles are collected by the cilia and taken up in the cytostome. The micronuclei of the conjugate divide meiotically to form four haploid nuclei in each cell. 5.49). To prepare further for Class 8 Science subject you can get Revision Notes, Important Questions at for free. The gametocytes are of two types, micro- and macro gametocytes, from which motile male gametes and non- motile female gametes are formed. Trichonympha 4. Moreover, diagrams are a beneficial tool to illustrate various concepts in biology. Disclaimer 9. In the classification … The protozoans digest the cellulose in the wood eaten by termites and convert it into carbohydrates that the termites can use. Explain the structure of stomata with a labelled diagram. In the mature stage they do not have any locomotion organelles and are non-motile. Also you can give online test and analyze your preparation level. It is the simplest of protozoans, found in the soil and freshwater bodies. 8. Of all species of Plasmodium, P. falciparum is the most dangerous and is the cause of ‘malignant’ malaria which is often fatal. Describe the nitrogen cycle with the help of a neat and labelled diagram. Draw a labelled diagram of Rhizopus. Protozoans: Useful and Harmful Protozoans (explained with diagram)! After reaching a certain size, the vacuole contracts to discharge the liquid contents through a pore situated in the pellicle. Plasmodium … Diagram of protozoa Trypanosoma by Food and agriculture organization of the united states. Trichonympha 4. Protozoans are the link in the food chain between unicellular algae and small aquatic organisms. Bacteria reproduce through binary fission, they split into two cells. This is a question and answer forum for students, teachers and general visitors for exchanging articles, answers and notes. This website includes study notes, research papers, essays, articles and other allied information submitted by visitors like YOU. He was a German palaeon- tologist, zoologist and botanist. MCQ Questions for Class 8 Science with Answers were prepared based on the latest exam pattern. Protozoan - Protozoan - Form and function: The protozoan cell carries out all of the processes—including feeding, growth, reproduction, excretion, and movement—necessary to sustain and propagate life. The protozoa ingest particles and convert cellulose to soluble carbohydrates which are taken up by the termites for their nourishment. Mosquitoes are known as the definitive host and the mammal as the intermediate host. Sexual reproduction takes place in the mosquito. Trypanosoma 3. Cell division occurs in the oocyst resulting in the formation of large number of sporozoites which are liberated by rupture of the oocyst wall. ‘Protozoa’, in fact, means ‘the first animal’. At the base of each cilium, there is a basal granule situated in the cytoplasm. Write 10 lines on the usefulness of microorganisms in our lives. The diploid micronucleus then divides three times by mitosis to form eight nuclei. Some protozoans cause diseases. Thus, Giardia has a simple life-cycle having only two types of growth form — an active trophozoite stage and an inactive cyst stage. In microorganism class 8 notes, the classification of microbes and their various characteristics along with chapter MCQs are discussed. You may have seen some of these unicellular organisms in the drop of pond water you observed under the microscope. The causal organism is L. donovani. Infections caused by Trypanosoma are known as trypanosomiasis and commonly as sleeping sickness. The cytoplasm having a higher osmotic pressure than the surrounding water absorbs water by osmosis. The largest protozoa are called xenophyophores, which can measure up to 20 centimeters in diameter. Content Filtrations 6. Maha Board Class 8thGeneral Science Textbook All Questions. As they enter through a bite in the skin, they lose their flagella and become ovoid non-flagellate bodies (amastigotes) measuring 2-4 μm x 1-2 μm. 5.49). What are insulators or poor conductors? The cells have a wide clear ectoplasm which is more retractile than the more or less homogeneous endoplasm. Asexual reproduction occurs in the mammalian host. Content thus produced is ready for television, film and the internet. A characteristic feature is the presence of two types of nuclei — a macronucleus and one or two micronuclei. Answer Now and help others. Content Guidelines 2. Ringworm is caused by fungi. Trypanosoma spp. The basal granules are interconnected by a system of fine fibrils to form a ciliary complex. Of these nuclei, three degenerate, and the remaining nucleus divides mitotically to produce two nuclei. Explore top 12 diseases caused by protozoa namely malaria, Amoebiasis, Trypanosomiasis, Chagas disease, Lambliasis, Babesiosis. Paramoecium is another freshwater protozoan found in ponds and ditches. ADVERTISEMENTS: The following points highlight the top nine examples of protozoa. These solutions for Combustion And Flame are extremely popular among Class 8 students for Science Combustion And Flame Solutions come handy for quickly completing your homework and preparing for exams. PROTOZOA They are eukaryotic organisms which means that they have a membrane-bound nucleus and organelles. One functions as the micronucleus of the Tetrahymena cell, and the remaining four nuclei form a macronucleus. Draw a neat and well-labelled diagram of Spirogyra. Explore the structure of bacteria, classification of bacteria and its reproduction. Maharashtra Board Class 8 for General Science. Before publishing your articles on this site, please read the following pages: 1. Like all membranous structures in the eukaryotic cell, the plasma membrane is composed of mostly lipid and some protein molecules. Privacy Policy3. The American type, prevalent in central and south America, is also known as Chagas’ disease (named after the discoverer Carlos Juan Chagas). Everything, from the cross-section of a plant cell to onion tissues, helps to educate students about the various anatomical structures, functions, and their implications. Sexual reproduction takes place by conjugation of two paramecia belonging to different mating types. The food is digested with the help of enzymes and the undigested materials are excreted from the cells through a posteriorly situated cytoproct (an anal opening). Plasmodia are sporozoa belonging to the Phylum Apicomplexan. Paramecium (also Paramoecium, / ˌ p ær ə ˈ m iː ʃ (i) ə m /, PARR-ə-MEE-sh(ee-)əm, /-s i ə m /, -⁠see-əm) is a genus of unicellular ciliates, commonly studied as a representative of the ciliate group. The parasite is oval-shaped and has flagella. Several species of the genus Plasmodium, like P. vivax, P. ovale, P. malariae and P. falciparum are etiological agents of malaria, one of the greatest killer diseases that affects 200 to 300 million people yearly. Amoebiasis is a common intestinal infection in the tropical countries. The pellicle is a more or less firm covering, often variously ridged and sculptured. Well and easy explanation with pictures. For mobility in the viscous plasma, the cells are provided with an undulating membrane which is externally bordered by a flagellum. They form the principal diet of blue whales, who gulp them in with sea water. In other words, they eat algae and are eaten by small fish and other organisms. Some protozoans live in the body of other organisms and help them. The lesson covers the complete explanation of class 8 Chapter 2 Microorganisms.Topics covered are Introduction to Micro-organisms and microbiology, different types of Micro-organisms, Useful and Harmful Micro-organisms. In humans, the organisms thrive in blood and cerebrospinal fluid and assume a non-flagellated form. Watch Queue Queue Toxoplasma gondii, the cause of toxoplasmosis is an Apicomplexan sporozoan. The active feeding stage of E. histolytica are known as trophozoites. The gametocytes present in the blood are sucked in by the mosquito when it bites an infected person. The protozoan then divides by binary fission to produce progenies, each of which has a diploid micronucleus and a polyploid macronucleus. In this form they remain in the saliva of sand flies. Check the below NCERT MCQ Questions for Class 8 Science Chapter 2 Microorganisms: Friend and Foe with Answers Pdf free download. Binary fission replication . [MSE (Chandigarh) 2005, 2007] Answer: Question 2. are haemoflagellates thriving in the circulatory system of the host. Other species, like Entamoeba coli and E. gingivalis are harmless commensal organisms. There is commonly a single nucleus and the cells in parasitic stage often contain ingested red blood cells (Fig. Which part of the male reproductive system store the sperm? One of these remains within the cell, while the other passes into the partner cell, i.e., both cells exchange one nucleus each. Chemical Effects of Electric Current Class 8 Extra Questions Science Chapter 14 Chemical Effects of Electric Current Class 8 Extra Questions Very Short Answer Questions Question 1. 3. Protozoa is classified by many based on different characters of protozoa but the classification of Protozoa is complicated and difficult The classification followed here is based on Hyman's classification.. Phylum Protozoa is divided into two subphyla: Sub-phylum Plasmodroma:. Prohibited Content 3. The applications of various helpful microorganisms are explained in the class 8 science chapter 2 notes. The merozoites liberated by rupture of red blood cells of an infected person can invade new red blood cells to repeat an asexual cycle of multiplication. Welcome to BiologyDiscussion! Reproduction. The trophozoites .are formed from the cysts. What are good conductors? The symptoms are usually mild in normal human individuals, but may be dangerous in AIDS patients with impaired immune system. This is the infective form of leishmanias. Perhaps you remember that Amoeba engulfs food with the help of pseudopodia. They are also heterotrophic meaning they rely on the environment for their nutrition. Giardia intestinalis (= Giardia lamblia) is an intestinal parasite causing diarrhoeal diseases in man. Explore more about viruses at BYJU'S Like other genera of sporozoa, they are obligate parasites and the cells are with an apical complex of several organelles. Class 8 Study Material – Notes, Important Questions, Practice Tests. It is a widespread parasite of humans and other vertebrates and it spreads through domestic cats. Free PDF Download - Best collection of CBSE topper Notes, Important Questions, Sample papers and NCERT Solutions for CBSE Class 8 Science Microorganisms - Friend and Foe. It is an intestinal parasite which is transmitted passively through food and water. The cells have a characteristic shape, looking like a slipper having a broad anterior rounded end and a comparatively narrower rounded posterior end. The macronucleus is involved in cellular functions, while the micronucleus takes part in reproduction. Protozoan, organism, usually single-celled and heterotrophic (using organic carbon as a source of energy), belonging to any of the major lineages of protists and, like most protists, typically microscopic. After 4 to 7 days, the trophozoites are transformed into cysts and are excreted in feces. Plasmodium 7. Our notes of Chapter 2 Microorganisms : friend and foe areprep ared by Maths experts in an easy to remember format, covering all syllabus of CBSE, KVPY, NTSE, Olympiads, NCERT & other Competitive Exams. This is a protozoan that causes sleeping sickness. The cytoplasm is covered by a flexible pellicle. The entire NCERT textbook questions have been solved by best teachers for you. These pass into the grazing animals and to humans through consumption of undercooked beef, pork or mutton. You may have seen some of these unicellular organisms in the drop of pond water you observed under the microscope. The genus belongs to the Phylum Sarcomastigophora, Sub-phylum Mastigophora and class Zoomastigophora. Entamoeba 6. There is another flagellum which remains free and attached at the anterior end of an elongated leaf-like cell. Bacteria are prokaryotic, single-celled microscopic organisms present almost everywhere. This video is unavailable. Infections range from asymptomatic to life threatening, depending on the species and strain of the parasite and the resistance of the host. Leishmania 5. Besides, the smallest is 1 to 10 μm long (intracellular form). Two different types of sleeping sickness diseases are recognized — the African sleeping- sickness caused by Trypanosoma brucei and American sleeping sickness caused by Trypanosoma cruzi. Moreover, they are herbivores, carnivores, and omnivores. Microorganisms Class 8 Science Chapter 2 as per NCERT Book used in CBSE and other Schools. Share Your PDF File A virus is a microscopic, infectious agent that replicates only inside the living cells of an organism.organisms. The cells also contain contractile vacuoles which store water and increase in size. Share Your Word File Phylum protozoa is a large and varied group and possess a complication in its classification.. higher protests . CLASSIFICATION OF PROTOZOA. Examples include: 1. These solutions for Living World And Classification Of Microbes are extremely popular among Class 8 students for Science Living World And Classification Of Microbes Solutions come handy for quickly completing your homework and preparing for exams. Furthermore, the scientist has described more than 50 thousand species of Protozoa. Goldfuss erected Protozoa as a class containing what he believed to be the simplest animals. Protozoans serve as food for many small aquatic organisms. Most of the time, protozoans are microscopic. The protozoa get in return a safe habitat and food in the form of cellulose present in the wood eaten by the termites. They are, thus, useful in the treatment of sewage. The life-cycle has four important stages — the sporozoite, the merozoite, the gametocyte and the gamete. The oocytes germinate to produce eight sporozoites which give rise to the trophozoites (also called tachyzoites). Classification. Three of the eight nuclei degenerate. Plasmodium 7. Essentially, protozoa are single-celled eukaryotes.This means that they are single celled organisms that have a nuclei as well asa number of other important organelles within the cytoplasmand enclosed by amembrane. 5.49). Infection occurs by ingestion of cysts through food and water.