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Protistas: organismos eucariotas unicelulares
- 1. PROTISTAS Son organismos Eucariotas unicelulares La mayoría son microscópicos Algunos son coloniales Viven en todos los ambientes Dra. Vanessa Rocha Calani
- 2. Los Protistas son un Reino de eucariotas extremadamente diverso Los Protistas lo forman varios tipos dentro del dominio Eukarya Los Protistas obtienen sus nutrientes de varias formas – Las Algas son protistas autótrofos – Los Protozoos son protistas heterótrofos, se alimenta de bacterias y otros protistas. Los estudiaremos porque son los más parecidos a los animales – Los Protistas del tipo hogo obtienen las moléculas orgánicas por absorción
- 5. CARACTERISTICAS Los Protistas son eucariotas con: – Cromosomas rodeados de una membrana (núcleo) – Multiples cromosomas – Flagelos o cilios con un diseño de 9 + 2 microtubulos Algunos protistas tiene un nivel de complejidad celular muy alto ¿Como lo han alcanzado? ¿Cuál es su origen? La célula eucariota compleja apareció y evolucionó cuando algunos procariotas invadieron a otros procariotas de mayor tamaño. Hipótesis Endosimbionte de L. Margulis
- 7. Eucariotas autótrofos Núcleo Núcleo Cloroplasto Alga verde Cloroplasto Alga roja Núcleo Endosimbiosis primaria Cianobacteria Eucariota heterótrofo Transformada en un cloroplasto
- 8. Eucariotas heterótrofos Eucariotas autótrofos Núcleo Núcleo Cloroplasto Alga verde Cloroplasto Alga roja Núcleo Endosimbiosis primaria Cianobacteria Eucariota heterótrofo Transformada en un cloroplasto
- 9. Endosimbiosis secundaria Eucariotas heterótrofos Eucariotas autótrofos Núcleo Núcleo Cloroplasto Alga verde Cloroplasto Alga roja Núcleo Endosimbiosis primaria Cianobacteria Eucariota heterótrofo Transformada en un cloroplasto Endosimbiosis secundaria
- 10. Restos de un Alga verde Euglenozoos Restos de un Alga roja Dinoflagelados Apicomplejos Stramenopilos Endosimbiosis secundaria Eucariotas heterótrofos Eucariotas autótrofos Núcleo Núcleo Cloroplasto Alga verde Cloroplasto Alga roja Núcleo Endosimbiosis primaria Cianobacteria Eucariota heterótrofo Transformada en un cloroplasto Endosimbiosis secundaria
- 11. Diplomonadinos Mohos acuáticos Parabasalidos Euglenozoos Dinoflagelados Apicomplejos Ciliados Algas pardas Diatomeas Foraminiferos Radiolarios Algas rojas Clorofitos Charofitos Plantas terrestres Algas verdes Amebas Mohos mucilaginosos Hongos Coanoflagelados Animales AlveoladosAmebozoosEstramenopilos
- 12. Los Euglenozoos son un clado de los protistas con movimiento – Su rasgo común es la posesión de una varilla cristalina de función desconocida entre sus flagelos En este grupo se incluyen organismos heterótrofos, fotosintéticos (autótrofos) y parásitos patógenos Copyright © 2009 Pearson Education, Inc. Diplomonadinos Parabasalidos Euglenozoos
- 13. Se desplazan mediante “flagelos” Se reproducen asexualmente por “bipartición longitudinal” Los hay “autótrofos” y “heterótrofos”, de vida libre y “endosimbiontes” Algunos causan serias enfermedades
- 14. ESQUEMA DE UN FLAGELADOESQUEMA DE UN FLAGELADO (Euglena)(Euglena)
- 16. Video: Euglena Video: Movimiento de Euglena
- 17. Los Dinoflagelados son integrantes de gran importancia del fitoplancton marino y dulceacuícola – Algunos viven dentro de los pólipos del coral, alimentando a esas comunidades – Algunas especies causan las “mareas rojas” Los Ciliados tienen numerosos cilios que usan para el movimiento y para capturar su alimento Los Apicomplejos son parásitos de animales y entre ellos está el Plasmodium, que causa la malaria Copyright © 2009 Pearson Education, Inc. Los Alveolados tienen una saco debajo de la membrana plasmática Dinoflagelados Apicomplejos Ciliados Alveolados
- 19. CICLO BIOLÓGICO DECICLO BIOLÓGICO DE Plasmodium vivaxPlasmodium vivax yy P. falciparumP. falciparum El ciclo comienza a) cuando una hembra de mosquito Anopheles pica a una persona con malaria y, junto con la sangre, succiona gametas indiferenciadas b) del esporozoo. En el tracto digestivo del mosquito, las gametas se diferencian, se unen, c) y forman un cigoto, d). A partir de los cigotos se desarrollan estructuras multinucleadas llamadas oocistos, e) que, en unos pocos días, se dividen en miles de células fusiformes muy pequeñas, los esporozoítos, f). Éstas luego migran a las glándulas salivales del mosquito. Cuando la hembra pica a otra víctima, g), la infecta con los esporozoítos. Éstos primero entran a las células hepáticas, h), donde sufren divisiones múltiples, i). Los productos de estas divisiones (merozoítos) entran a los glóbulos rojos, j), donde nuevamente se dividen en forma repetida, k), rompen los glóbulos rojos, 1) a intervalos regulares de aproximadamente 48 horas; así, provocan episodios febriles recurrentes que son característicos de esta enfermedad. Después de un período de reproducción asexual, parte de los merozoítos se transforman en gametas indiferenciadas (m) y, si son ingeridos por un mosquito en este estadio, el ciclo comienza nuevamente. Los Apicomplejos
- 20. Los CiliadosLos Ciliados Se desplazan mediante “cilios” Tienen forma constante Suelen poseer varios núcleos de diferente tamaño (macro- y micro-núcleos) La mayoría son de vida libre en ambientes acuáticos Se reproducen asexualmente por “bipartición”, y sexualmente por “conjugación”
- 21. EQUEMA DE UN CILIADOEQUEMA DE UN CILIADO (Paramecium)(Paramecium) Stentor Macronúcleo Cilios
- 22. Video: Cilios de Paramecium Video: Vacuola de Paramecium Video: Vorticella Video: Vorticella Video: Vorticella
- 23. Los Amebozoos tienen pseudópodos del tipo lobópodo Las Amebas se mueven y se alimentan por medio de los pseudópodos Los miembros del clado amebozoos incluyen muchas amebas de vida libre, algunas parásitas y los mohos de mucílago – Todos tienen lobópods Copyright © 2009 Pearson Education, Inc. Amebas Amebozoos
- 24. LAS AMEBAS O RIZÓPODOSLAS AMEBAS O RIZÓPODOS •Se mueven medianteSe mueven mediante “seudópodos” •Pueden tener uno o varios núcleos, pero todos igualesPueden tener uno o varios núcleos, pero todos iguales •La mayoría son de vida libre, algunas ectocomensalesLa mayoría son de vida libre, algunas ectocomensales y otras parásitasy otras parásitas •Pueden ser “desnudas” o “cubiertas”Pueden ser “desnudas” o “cubiertas” •Se reproducen asexualmente porSe reproducen asexualmente por “bipartición”
- 25. Video: Ameba Video: Ameba con pseudópodos
- 26. ALGUNOS PROTOZOOS CAUSAN GRAVES ENFERMEDADESALGUNOS PROTOZOOS CAUSAN GRAVES ENFERMEDADES El “dinoflagelado” Alexandrium minutum, causante de “mareas rojas”, produce toxinas con efectos paralizantes. El “zooflagelado” Trypanosoma brucei y T. gambiensis produce la “enfermedad del sueño” y Leishmania la leismaniosis, utilizando “dípteros” como transmisores La Entamoeba histolyica causa la “disentería amebiana” El “apicomplejo” Plasmodium (P. falciparum) produce la “malaria o paludismo” transmitido por el mosquito Anopheles El “pluriflagelado” Trichomonas vaginalis causa “vaginitis”
- 27. Animación deAnimación de CoanoflageladosCoanoflagelados Coanoflagelados Animales Hipótesis colonial, a partir de un flagelado. Los animales pluricelulares (metazoos), pues, serían un conjunto monofilético que incluiría a los coanoflagelados. Es apoyada por evidencias a partir de las secuencias del ARNr de 16s (subunidad ribosómica pequeña) y de otras semejanzas bioquímicas Diplomonadinos Mohos acuáticos Parabasalidos Euglenozoos Dinoflagelados Apicomplejos Ciliados Algas pardas * Diatomeas Foraminiferos Radiolarios Algas rojas * Clorofitos Charofitos * Plantas terrestres * Algas verdes Amebas Mohos mucilaginosos Hongos Coanoflagelados Animales AlveoladosAmebozoosEstramenopilos * multicelulares Uniconta Opistoconta * *
Notas del editor
- Remind your students that protist is not a taxon, but rather a convenient term for eukaryotes that are not plants, animals, or fungi. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally “better” than prokaryotes. The recognition that some prokaryotes have endured unchanged since nearly two billion years before eukaryotes appeared, and an appreciation of the tremendous diversity of prokaryotic lifestyles, might help to correct this misperception. After all, what eukaryotes can survive in the habitats of extremophiles? 2. Students might immediately expect for all symbiotic relationships to benefit both members. Consider noting that parasitism is a type of symbiotic relationship in which one member is harmed. 3. Students might think of protists as “simple” organisms in comparison to our own complex multicellular bodies. However, as the authors note, within a single cell protists must carry out all the basic functions performed by the set of specialized cells that collectively form the bodies of plants and animals. Teaching Tips 1. Consider referring to www.bact.wisc.edu/Microtextbook/. This website is a free and detailed microbiology textbook on the Internet. Since it is copyrighted, fair-use restrictions apply, but it is an excellent reference for instructors lacking extensive training in microbiology. 2. Much of this chapter describes the traits and habits of single-celled prokaryotes and eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by shape, mode of nutrition, or protozoan subgroup. 3. Students might easily be led to believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. 4. Students may need to be reminded that most prokaryotes are about a tenth the diameter of eukaryotic cells. Thus, by the process of primary endosymbiosis, symbiotic bacteria could easily fit within larger eukaryotic cells.
- Figure 16.11A Protists in pond water.
- Figure 16.11B Protists in termite gut covered by thousands of flagella, viewed with light microscope (left) and scanning electron microscope (right). Students may need to be reminded that most prokaryotes are about a tenth the diameter (and 1,000th the volume) of eukaryotic cells. Thus symbiotic bacteria fit easily within larger eukaryotic cells.
- Students might think of protists as simple systems compared to our complex bodies. However, within a single cell, protists must carry out all the basic functions performed by the set of specialized cells that collectively form the bodies of plants and animals. Some protists (such as ciliates) have enormously complex cells, far more complex than any one cell in the human body. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally “better” than prokaryotes. The recognition that some prokaryotes have endured unchanged since nearly two billion years before eukaryotes appeared, and an appreciation of the tremendous diversity of prokaryotic lifestyles, might help to correct this misperception. After all, what eukaryotes can survive in the habitats of extremophiles? 2. Students might immediately expect for all symbiotic relationships to benefit both members. Consider noting that parasitism is a type of symbiotic relationship in which one member is harmed. 3. Students might think of protists as “simple” organisms in comparison to our own complex multicellular bodies. However, as the authors note, within a single cell protists must carry out all the basic functions performed by the set of specialized cells that collectively form the bodies of plants and animals. Teaching Tips 1. Consider referring to www.bact.wisc.edu/Microtextbook/. This website is a free and detailed microbiology textbook on the Internet. Since it is copyrighted, fair-use restrictions apply, but it is an excellent reference for instructors lacking extensive training in microbiology. 2. Much of this chapter describes the traits and habits of single-celled prokaryotes and eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by shape, mode of nutrition, or protozoan subgroup. 3. Students might easily be led to believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. 4. Students may need to be reminded that most prokaryotes are about a tenth the diameter of eukaryotic cells. Thus, by the process of primary endosymbiosis, symbiotic bacteria could easily fit within larger eukaryotic cells.
- Figure 16.12 A hypothesis of the origin of protistan diversity through endosymbiosis (mitochondria not shown). 1. Explain Figure 16.12 to the students, explaining that the first step was primary endosymbiosis, as heterotrophic eukaryotes took in a cyanobacterium. The cyanobacterium continued to function within the host cell, with photosynthesis providing a steady source of food for the heterotrophic host and giving it a significant selective advantage. The cyanobacteria divided and were inherited when the host reproduced, evolving into the chloroplasts of red and green algae. 2. Green and red algae themselves became endosymbionts following ingestion by heterotrophic eukaryotes (secondary endosymbiosis). Algae survived as cellular organelles, replicated, and gave hosts a selective advantage. Ingestion of green algae euglenozoans. Ingestion of red algae dinoflagellates, apicomplexans, stramenopiles. Remnants of algae are still present within cells.
- Figure 16.12 A hypothesis of the origin of protistan diversity through endosymbiosis (mitochondria not shown). 1. Explain Figure 16.12 to the students, explaining that the first step was primary endosymbiosis, as heterotrophic eukaryotes took in a cyanobacterium. The cyanobacterium continued to function within the host cell, with photosynthesis providing a steady source of food for the heterotrophic host and giving it a significant selective advantage. The cyanobacteria divided and were inherited when the host reproduced, evolving into the chloroplasts of red and green algae. 2. Green and red algae themselves became endosymbionts following ingestion by heterotrophic eukaryotes (secondary endosymbiosis). Algae survived as cellular organelles, replicated, and gave hosts a selective advantage. Ingestion of green algae euglenozoans. Ingestion of red algae dinoflagellates, apicomplexans, stramenopiles. Remnants of algae are still present within cells.
- Figure 16.12 A hypothesis of the origin of protistan diversity through endosymbiosis (mitochondria not shown). 1. Explain Figure 16.12 to the students, explaining that the first step was primary endosymbiosis, as heterotrophic eukaryotes took in a cyanobacterium. The cyanobacterium continued to function within the host cell, with photosynthesis providing a steady source of food for the heterotrophic host and giving it a significant selective advantage. The cyanobacteria divided and were inherited when the host reproduced, evolving into the chloroplasts of red and green algae. 2. Green and red algae themselves became endosymbionts following ingestion by heterotrophic eukaryotes (secondary endosymbiosis). Algae survived as cellular organelles, replicated, and gave hosts a selective advantage. Ingestion of green algae euglenozoans. Ingestion of red algae dinoflagellates, apicomplexans, stramenopiles. Remnants of algae are still present within cells.
- Figure 16.12 A hypothesis of the origin of protistan diversity through endosymbiosis (mitochondria not shown). 1. Explain Figure 16.12 to the students, explaining that the first step was primary endosymbiosis, as heterotrophic eukaryotes took in a cyanobacterium. The cyanobacterium continued to function within the host cell, with photosynthesis providing a steady source of food for the heterotrophic host and giving it a significant selective advantage. The cyanobacteria divided and were inherited when the host reproduced, evolving into the chloroplasts of red and green algae. 2. Green and red algae themselves became endosymbionts following ingestion by heterotrophic eukaryotes (secondary endosymbiosis). Algae survived as cellular organelles, replicated, and gave hosts a selective advantage. Ingestion of green algae euglenozoans. Ingestion of red algae dinoflagellates, apicomplexans, stramenopiles. Remnants of algae are still present within cells.
- Figure 16.12 A hypothesis of the origin of protistan diversity through endosymbiosis (mitochondria not shown). 1. Explain Figure 16.12 to the students, explaining that the first step was primary endosymbiosis, as heterotrophic eukaryotes took in a cyanobacterium. The cyanobacterium continued to function within the host cell, with photosynthesis providing a steady source of food for the heterotrophic host and giving it a significant selective advantage. The cyanobacteria divided and were inherited when the host reproduced, evolving into the chloroplasts of red and green algae. 2. Green and red algae themselves became endosymbionts following ingestion by heterotrophic eukaryotes (secondary endosymbiosis). Algae survived as cellular organelles, replicated, and gave hosts a selective advantage. Ingestion of green algae euglenozoans. Ingestion of red algae dinoflagellates, apicomplexans, stramenopiles. Remnants of algae are still present within cells.
- Figure 16.13 A tentative phylogeny of eukaryotes, with indication of the module or chapter in which each group is covered
- Tell your students that Trypanosoma, spread by the tsetse fly, causes sleeping sickness and that Euglena is common in pond water. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally “better” than prokaryotes. The recognition that some prokaryotes have endured unchanged since nearly two billion years before eukaryotes appeared, and an appreciation of the tremendous diversity of prokaryotic lifestyles, might help to correct this misperception. After all, what eukaryotes can survive in the habitats of extremophiles? 2. The evolutionary relationships hypothesized in Figure 16.13 may require students to rethink the validity of groups explored in their prior studies. Consider noting that these revisions represent the tentative nature of science, in which no information is ever considered final. Teaching Tips 1. Consider referring to www.bact.wisc.edu/Microtextbook/. This website is a free and detailed microbiology textbook on the Internet. Since it is copyrighted, fair-use restrictions apply, but it is an excellent reference for instructors lacking extensive training in microbiology. 2. Much of this chapter describes the traits and habits of single-celled prokaryotes and eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by shape, mode of nutrition, or protozoan subgroup. 3. Students might easily be led to believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. 4. Students can be encouraged to create their own table of traits, resembling Table 16.2 in organization, to distinguish between the groups addressed in Modules 16.14–16.20. Alternately, you might create such a table to be completed by students while they study these modules. Beginning science students often need help learning how to organize information gained through reading and note taking. 5. The great diversity of protists presents an opportunity for students to report on different types of protists and enhance their knowledge. For example, students can sketch their protist and identify reliable Web resources for additional details and clarity. You might collect and edit these Web references to serve as an aid for your entire class. These short exercises in content ownership allow students to develop a greater depth of understanding and increase interaction with the subject.
- Figure 16.15A A euglenozoan: Trypanosoma (with blood cells).
- Figure 16.15B A euglenozoan: Euglena .
- Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally “better” than prokaryotes. The recognition that some prokaryotes have endured unchanged since nearly two billion years before eukaryotes appeared, and an appreciation of the tremendous diversity of prokaryotic lifestyles, might help to correct this misperception. After all, what eukaryotes can survive in the habitats of extremophiles? 2. The evolutionary relationships hypothesized in Figure 16.13 may require students to rethink the validity of groups explored in their prior studies. Consider noting that these revisions represent the tentative nature of science, in which no information is ever considered final. Teaching Tips 1. Consider referring to www.bact.wisc.edu/Microtextbook/. This website is a free and detailed microbiology textbook on the Internet. Since it is copyrighted, fair-use restrictions apply, but it is an excellent reference for instructors lacking extensive training in microbiology. 2. Much of this chapter describes the traits and habits of single-celled prokaryotes and eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by shape, mode of nutrition, or protozoan subgroup. 3. Students might easily be led to believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. 4. Students can be encouraged to create their own table of traits, resembling Table 16.2 in organization, to distinguish between the groups addressed in Modules 16.14–16.20. Alternately, you might create such a table to be completed by students while they study these modules. Beginning science students often need help learning how to organize information gained through reading and note taking. 5. The great diversity of protists presents an opportunity for students to report on different types of protists and enhance their knowledge. For example, students can sketch their protist and identify reliable Web resources for additional details and clarity. You might collect and edit these Web references to serve as an aid for your entire class. These short exercises in content ownership allow students to develop a greater depth of understanding and increase interaction with the subject.
- Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally “better” than prokaryotes. The recognition that some prokaryotes have endured unchanged since nearly two billion years before eukaryotes appeared, and an appreciation of the tremendous diversity of prokaryotic lifestyles, might help to correct this misperception. After all, what eukaryotes can survive in the habitats of extremophiles? 2. The evolutionary relationships hypothesized in Figure 16.13 may require students to rethink the validity of groups explored in their prior studies. Consider noting that these revisions represent the tentative nature of science, in which no information is ever considered final. Teaching Tips 1. Consider referring to www.bact.wisc.edu/Microtextbook/. This website is a free and detailed microbiology textbook on the Internet. Since it is copyrighted, fair-use restrictions apply, but it is an excellent reference for instructors lacking extensive training in microbiology. 2. Much of this chapter describes the traits and habits of single-celled prokaryotes and eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by shape, mode of nutrition, or protozoan subgroup. 3. Students might easily be led to believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. 4. Students can be encouraged to create their own table of traits, resembling Table 16.2 in organization, to distinguish between the groups addressed in Modules 16.14–16.20. Alternately, you might create such a table to be completed by students while they study these modules. Beginning science students often need help learning how to organize information gained through reading and note taking. 5. The great diversity of protists presents an opportunity for students to report on different types of protists and enhance their knowledge. For example, students can sketch their protist and identify reliable Web resources for additional details and clarity. You might collect and edit these Web references to serve as an aid for your entire class. These short exercises in content ownership allow students to develop a greater depth of understanding and increase interaction with the subject.
- Figure 16.16A Gymnodinium , a dinoflagellate that causes red tides. Explain that red tides are blooms of dinoflagellates like Gymnodinium with toxin accumulations that kill fish and humans.
- Explain how amoeba feed by ingesting smaller protists and prokaryotes with lobe-shaped pseudopodia. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally “better” than prokaryotes. The recognition that some prokaryotes have endured unchanged since nearly two billion years before eukaryotes appeared, and an appreciation of the tremendous diversity of prokaryotic lifestyles, might help to correct this misperception. After all, what eukaryotes can survive in the habitats of extremophiles? 2. The evolutionary relationships hypothesized in Figure 16.13 may require students to rethink the validity of groups explored in their prior studies. Consider noting that these revisions represent the tentative nature of science, in which no information is ever considered final. Teaching Tips 1. Consider referring to www.bact.wisc.edu/Microtextbook/. This website is a free and detailed microbiology textbook on the Internet. Since it is copyrighted, fair-use restrictions apply, but it is an excellent reference for instructors lacking extensive training in microbiology. 2. Much of this chapter describes the traits and habits of single-celled prokaryotes and eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by shape, mode of nutrition, or protozoan subgroup. 3. Students might easily be led to believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. 4. Students can be encouraged to create their own table of traits, resembling Table 16.2 in organization, to distinguish between the groups addressed in Modules 16.14–16.20. Alternately, you might create such a table to be completed by students while they study these modules. Beginning science students often need help learning how to organize information gained through reading and note taking. 5. The great diversity of protists presents an opportunity for students to report on different types of protists and enhance their knowledge. For example, students can sketch their protist and identify reliable Web resources for additional details and clarity. You might collect and edit these Web references to serve as an aid for your entire class. These short exercises in content ownership allow students to develop a greater depth of understanding and increase interaction with the subject.
- Figure 16.18A An amoeba ingesting a smaller protist.