-not included in the land plant, fungal or animal kingdoms

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1 Chapter 19- Protists and the Origin of Eukaryotic Cells Protists are organisms that: -not included in the land plant, fungal or animal kingdoms -often microscopic in size -occur most commonly in aquatic habitats Algae are groups of protists that: -contain one or more plastids -usually photosynthetic Algae are autotrophic which means they can produce their own organic food. Protozoa is an informal name for various groups of protists that lack plastids (not photosynthetic). Protozoa are: -single-celled -mobile organisms -heterotrophic Heterotrophic- must obtain organic food from outside their bodies How can protists be distinguished from plants, fungi, and animals? Protists are eukaryotic organisms that are not included in the land plant, fungi, and animal kingdoms, because they lack characteristics that typify these other kingdoms.

2 Protists are common and numerous in aquatic and moist habitats. Most protists reproduce and grow best in moist habitats: -freshwater ponds, streams, and lakes -ocean waters -soil water -moist tissues and cells of animals or plant bodies Some protists live cooperatively within hosts Ex: Dinoflagellate living within the tissues of corals and other marine animals. Endosymbiont Microscopic protists move in several ways: Many protists bear one or more flagella, a long propelling extension from the cells Many protists have immobile or multicellular bodies for much of their life cycle, but produce flagellate reproductive cells.

3 Cilia are structures that are internally similar to flagella, but shorter and more abundant on cells. Ciliates have cilia that extend from part or all surfaces of nonalgal protists. Ciliates are often larger than flagellates. Protists include diverse groups whose relationships are not completely known. Biologists examine protist diversity and relationships by comparing cell structure and DNA sequences. These data indicate that eukaryotes (protists, fungi, animals, and plants) may have a common ancestor. Protists do not form a single monophyletic clade (a group of organisms descended from a common ancestor).

4 Algae are grouped with the protists based on: Algae morphology may be: -unicellular -aggregates of cells (colonies) Mallamonas -cells joined end-to-end to form filaments -composed of tissues whose cells communicate and are specialized (multicellularity) Seaweeds are examples of macroscopic protists. Major groups of algae and distinguishing features.

5 Euglenoids (in Discicristates) -in a group of flagellates that includes the kinetoplastids -the kinetoplastids include trypanosomes, a group of non-photosynthetic parasites that infect mammals, fish, and plants Trypanosoma Euglenoids - typically flagellated orum/viewtopic.php?t=3193&highli ght=euglena -many relatives have green plastids

6 Euglenoids Some euglenoids have a distinct motion called metaboly, that allows movement through moist soil. Cryptomonads ( hidden single cells ) -mostly single-celled flagellates -red, blue-green, olive, or colorless plastids -commonly occur in marine and freshwater -readily consumed by other protists and zooplankton ryptomonads are important members of the planktonic ood web: Dinoflagellates (in Alveolates) The dinoflagellates, together with ciliate protozoa and a group of parasites known as the apicomplexans make up the Alveolates. Plasmodium Plasmodium is the agent of malaria and infects 40% of the world s population, with up to 500 million cases, and 2.7 million deaths per year. (d) An apicomplexan: Plasmodium

7 Dinoflagellates (in Alveolates) These organisms are grouped together because they all have membranous sacs known as alveoli at the edges of their cells. These are known as the armored dinoflagellates. Dinoflagellates with little or no cellulose are unarmored or naked dinoflagellates. Although many dinoflagellates have plastids and are autotrophic, many dinoflagellates are heterotrophic and feed by ingesting food particles. Dinoflagellate plastids originated from a variety of eukaryotic algae that were originally digested as food. Some photosynthetic marine dinoflagellates generate harmful ocean blooms or red tides. These blooms are responsible for: Dinoflagellate poisons occur through production of various toxins that cause: Pfiesteria Harmful blooms result from eutrophic conditions (excess nutrients in the water) which arise from:

8 Haptophytes -flagellates or colonies of floating cells -some have golden-colored plastids -occur in mostly marine systems Some of the haptophytes have a modified flagellum called a haptonema for which the group is named. Some members of this group have a covering of detailed calcium carbonate scales known as coccoliths. Along with carbonate-shelled protozoa, haptophytes produce huge chalk deposits about 100 million years ago (White Cliffs of Dover) Stramenopiles Highly diverse algal lineage that includes both tiny flagellates and giant seaweeds. Stramenopiles are named for the distinctive straw-like hairs on one of the two flagella. Because the two flagella are structured differently, members of this group are also called the heterokonts. Synurophyceae Stramenopiles include: Some oomycetes are parasites that cause widespread diseases in seaweeds, molluscs, fish, and terrestrial crop plants. Mallamonas Chyrsophyceae he oomycete Phytophthora caused the historic Irish potato crop failure. Stramenopiles include: -many types of algae with golden-brown colored plastids Dinobryon du/starcentral/micro scope/portal.php?p agetitle=assetfactsh eet&imageid=27292

9 Stramenopiles include: Many large brown algae known as kelps form extensive forests in cold and temperate coastal oceans Red algae (Rhodophyta) -usually occur in marine waters Gelidium Porphyra Corallina The simplest red algae are microscopic single cells, some of which occur in hot, acidic freshwater. Batrachospermum Commercial use of red algae Porphyridium Annual harvest of red algae approximately 1 million tons, both cultivated and natural populations. 1) 2) Many red algae are used for food, but the most important are species of Porphyra. Nori is widely cultivated in Japan, Korea, and China.

10 Cell walls- Red algae (Rhodophyta) Cellulose forms the microfibrillar framework in most rhodophycean cell walls. In all other red algae, amorphous polysaccharides or mucilages occur between the cellulose microfibrils. Cellulose Fine structural study of the red seaweed Gymnogongrus torulosus (Phyllophoraceae, Rhodophyta) José M. Estevez 1 and Eduardo J. Cáceres 2 Agarose The two largest groups of amorphous mucilages are: Agar Agar is obtained commercially from only a few red algae, know collectively as agarophytes. Carrageenan is obtained from the Irish moss, Chondrus crispus. Gelidium Chondrus crispus

11 Red algae (Rhodophyta) Red algae are noted for their inability to produce flagella in any life stage. Green algae (Chlorophyta) -flagellated or have flagellated reproductive stages -freshwater, marine, and terrestrial -chlorophyll a and b (green in color) Green algae (Charophyceans) One subgroup of the green algae, the charophyceans (Charophyta), are ancestral to land plants.

12 Green algae (Charophyceans) Comparative studies of charophycean green algae and modern relatives of the earliest land plants help us to understand how plants first colonized land. VIRIDIPLANTAE

13 Chapter 19-Protists and the Origin of Eukaryotic Cells Algae and other protists have been useful in the discovery of how and in what order eukaryotic cells acquired structural features that distinguish them from prokaryotes. The eukaryotic nucleus and endomembrane system are thought to have originated by in-folding of the cell membrane in an ancestor of modern eukaryotic cells. Modern protist lineages, fungi,animals, and plants inherited mitochondria from early protists. Molecular evidence supports the idea that mitochondria originated from endosymbiotic protobacterial cells. Because mitochondria (and structures derived from them) occur in most eukaryotes, these organelles may have been present in early protists. Primary plastids originated from endosymbiotic cyanobacteria. Because all modern eukaryotic organisms known to contain plastids also possess mitochondria, it is thought that algae acquired plastids after mitochondria through endosymbiosis. The process by which an endosymbiotic cyanobacterium is engulfed and transformed into a plastid is known as primary endosymbiosis.

14 Some protists have acquired plastids from eukaryotic algal cells, a process known as secondary or tertiary endosymbiosis.

15 eproductive cycles in protists All protists are able to reproduce by asexual reproduction that involve mitotic divisions. Examples of the three main types of sexual life cycles are found among algal protists.

16 Study questions for Chapter 19-Protists and the Origin of Eukaryotic Cells What are 3 characteristics of protists? What are the general characteristics of algae? Define autotrophic. Give an example. Define protozoa. What are 3 characteristics of protozoa? Define heterotrophic. Give an example. How can protists be distinguished from plants, fungi and animals? Define plankton. Define phytoplankton. Define zooplankton. List the habitats where you would find protists. Define endosymbiont. Give an example. Distinguish between flagella and cilia. Name an alga with a flagellum/or flagella. Name a group of protozoa with cilia. Define monophyletic. Protists include diverse groups whose relationships are not completely known. Do protists form a single monophyletic group? Algal morphology is diverse. Label the images below with following terms: -unicellular -colonies -filaments -multicellular -large macroscopic cells

17 Study questions for Chapter 19-Protists and the Origin of Eukaryotic Cells Euglenoids Define kinetoplastids. What is a pellicle? What is paramylon? What is metaboly in euglenoids? Cryptomonads What does the word cryptomonad mean? Dinoflagellates Define alveolates. What are alveoli in dinoflagellates? Distinguish between a naked and an armored dinoflagellate? What is a bloom or red tide? What are some of the consequences of toxic algal blooms? Define eutrophic. Why do some harmful algal blooms occur? Haptophytes What is a haptonema? What are coccoliths? Why are haptophytes associated with the White Cliffs of Dover? Stramenopiles/Heterokonts What does stramenopile mean? What does heterokont mean? What algae are included in the Stramenopiles? Which member of the Oomycota caused the historic Irish potato famine? What is a diatom? What is a frustule? What are diatom cell walls made of? Which class included in the Stramenopiles includes brown kelps? What does phaeo mean? Rhodophyta What does rhodo mean? Name two freshwater genera in the Rhodophyta? What are the 2 largest groups of amorphous mucilages? Agar is obtained from which algal genus? Carrageenan is obtained from which algal species? What is agar used for? What is carrageenan used for? What is the triphasic life cycle in red algae? Green Algae Chlorophyta Charophyta Why are members of the Charophyta important in the evolutionary history of plants? The Origin of Eukaryotic Cells Where did the nucleus and endomembrane system originate? Where did modern protist lineages, fungi, animals and plants inherit mitochondria? Define primary plastid. Define secondary plastic. Define primary endosymbiosis. Define secondary or tertiary endosymbiosis.

18 Study questions for Chapter 19-Protists and the Origin of Eukaryotic Cells Three characteristics for each algal group. Euglenoids Cryptomonads Dinoflagellates Haptophytes Stramenopiles/Heterokonts Matching-Stramenopiles/Heterokonts Bacillariophyceae (diatoms) Phaeophyceae (brown algae) Chrysophyceae Oomycota A. B. C. D. Chyrsophyceae Dinobryon Rhodophyta (Red algae) Chlorophyta (green algae) Gelidium Porphyra Corallina Volvox Charophyta (green algae most closely related to land plants)