Questions and Answers
What is a characteristic feature of Euglenids?
Trypanosoma gambiense causes Chagas' disease.
False
Dinoflagellates are abundant components of both marine and freshwater _______________.
phytoplankton
Match the following groups with their characteristics:
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What is the name of the disease caused by another pathogenic trypanosome?
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The SAR supergroup is universally accepted as monophyletic.
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What is the characteristic feature of Apicomplexans?
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Apicomplexans have only asexual stages.
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What is the name of the parasite that causes malaria?
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Ciliates have large ______________________ and small micronuclei.
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What is the function of cilia in Ciliates?
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Match the following Alveolates with their characteristics:
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What is the process by which a unicellular organism engulfs another cell, which becomes an endosymbiont and then an organelle in the host cell?
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Mitochondria are believed to have evolved by endosymbiosis of a photosynthetic cyanobacterium.
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Diatoms have a sexual stage called conjugation.
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What composes much of the sediments known as diatomaceous earth?
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What is the name of the pathogen that causes yeast infections in human females?
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Diplomonads have modified mitochondria called _______________________.
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Match the following protist groups with their characteristics:
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What is the name of the organelle found in diplomonads that is involved in anaerobic biochemical pathways?
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What is a characteristic shared by most protists?
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Protists are classified into only two supergroups: Excavata and SAR.
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What is the term for the process by which an organism engulfs another cell, leading to the formation of organelles?
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Some protists are ______________________, obtaining energy by ingesting or absorbing nutrients.
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Match the following protist characteristics with their definitions:
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How do some protists obtain nutrients?
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All protists are autotrophic.
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Primary endosymbiosis occurs when a heterotrophic eukaryote consumes a ______________________ cell, leading to the formation of red or green algae.
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What is unique about the cytoskeleton of Excavates?
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Parabasalids are known to produce oxygen as a byproduct of their energy production
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What is the name of the disease caused by Trypanosoma?
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Euglenozoa have rod-shaped _______________________.
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Match the following Excavate subgroups with their characteristics:
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What is a characteristic feature of Alveolates?
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Stramenopiles can be only photoautotrophic.
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What is the name of the disease caused by Plasmodium?
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Dinoflagellates can be found in ______________________ environments.
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Match the following Alveolates with their characteristics:
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What is a characteristic feature of Diatoms?
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Ciliates can only reproduce asexually.
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What is the name of the pigment that gives Golden Algae their characteristic color?
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Brown Algae are found in ______________________ environments.
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What is the term for the process by which an organism engulfs another cell, leading to the formation of organelles?
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What is a characteristic feature of Brown Algae?
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Red Algae obtain their color from an abundance of the pigment chlorophyll.
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What is the term for the process by which Brown Algae undergo an alternation of generations?
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Green Algae are characterized by their ______________________ shape.
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Which of the following is an example of a Green Algae?
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Match the following Algae groups with their characteristics:
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Volvox is a type of Brown Algae.
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Stramenopiles are characterized by having two flagella, one ______________________ and one hairy.
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What is the characteristic feature of amoeboid protists?
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Ryze area is a subgroup of Uniconta protists.
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What is the common feature of Foraminifera and Radialarians?
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Uniconta is a clade that includes protists, animals, and ______________________.
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Which of the following is an example of a Uniconta protist?
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Entamoebas are parasites of the gastrointestinal system of mammals.
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Match the following amoeboid protists with their characteristics:
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What is the term for the extensions of cytoplasm used for locomotion and capturing prey in amoeboid protists?
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What happens to the merozoites after they penetrate the red blood cells?
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Ciliates have only one type of nucleus.
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What is the process by which genetic variation occurs in Ciliates?
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Sporozoites infect _______________________ cells.
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Match the following stages in the life cycle of Plasmodium with their descriptions:
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What is the characteristic feature of Alveolates?
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Apicomplexans have only asexual stages.
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What is the name of the parasite that causes malaria?
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Brown Algae are found in _______________ environments.
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Match the following Alveolates with their characteristics:
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All Brown Algae are unicellular.
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What is the term for the process by which Brown Algae undergo an alternation of generations?
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What is the type of life cycle that brown algae Laminaria has?
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What role do protists play in their habitats?
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Some protists are parasitic.
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What is the name of the disease caused by Pfiesteria shumwayae?
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Photosynthetic protists are limited by ______________________ in aquatic environments.
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Match the following protist groups with their characteristics:
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What happens to the biomass of photosynthetic protists when sea surface temperature increases?
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Study Notes
Apicomplexans
- Are parasites of animals and cause serious human diseases
- Spread through their host as infectious cells called sporozoites
- Have a complex of organelles at one end (apex) for penetrating host cells and tissues
- Have sexual and asexual stages that require two or more different host species to complete
- Plasmodium is an apicomplexan that causes malaria and requires both mosquitoes and humans to complete its life cycle
- Approximately 900,000 people die each year from malaria
Ciliates
- Are a large and varied group of protists that use cilia to move and feed
- Have large macronuclei and small micronuclei
- Genetic variation results from conjugation, a sexual process in which two individuals exchange haploid micronuclei
- Conjugation is separate from reproduction, which generally occurs by binary fission
Stramenopila
- Includes important phototrophs and heterotrophs
- Most have a "hairy" flagellum paired with a "smooth" flagellum
- Includes diatoms, golden algae, brown algae, and oomycetes
Diatoms
- Are unicellular algae with a unique two-part, glass-like wall of hydrated silica
- Are a major component of phytoplankton and are highly diverse
- Fossilized diatom walls compose much of the sediments known as diatomaceous earth
- Reproduction is mainly asexual
Euglenozoa
- Is a diverse clade that includes euglenids and kinetoplastids
- Some are predatory heterotrophs, photosynthetic autotrophs, and parasites
- Distinguished by a spiral or crystalline rod of unknown function inside their flagella
- Euglenids have one or two flagella that emerge from a pocket at one end of the cell
- Kinetoplastids have a single mitochondrion with an organized mass of DNA called a kinetoplast
- Include free-living consumers of prokaryotes in freshwater, marine, and moist terrestrial ecosystems
- Trypanosoma gambiense causes sleeping sickness in humans, and another pathogenic trypanosome causes Chagas' disease leading to congestive heart failure
SAR
- Is a supergroup that may have originated by a secondary endosymbiosis event with a red alga
- Includes the alveolates and the stramenopiles
Alveolata
- Are a sub-group of SAR that have membrane-bounded sacs (alveoli) just under the plasma membrane
- Function of alveoli is unknown
- Includes dinoflagellates, apicomplexans, and ciliates
Dinoflagellates
- Have two flagella and each cell is reinforced by cellulose plates
- Are abundant components of both marine and freshwater phytoplankton
- Are a diverse group of aquatic phototrophs, mixotrophs, and heterotrophs
- Toxic "red tides" are caused by dinoflagellate blooms
Endosymbiosis and Protist Evolution
- Endosymbiosis is the process in which a unicellular organism engulfs another cell, which becomes an endosymbiont and then organelle in the host cell
- Mitochondria are believed to have evolved by endosymbiosis of an aerobic prokaryote
- Plastids are believed to have evolved by endosymbiosis of a photosynthetic cyanobacterium
Introduction to Protists
- Protists are diverse eukaryotic organisms varying in shape, size, and patterns, with different numbers and types of organelles.
- The kingdom Protista was dismantled in the 1990s, and now protists are classified into four supergroups: Excavata, SAR, Archaeplastida, and Opisthokonta.
Characteristics of Protists
- Most protists are unicellular, but some form colonies or are multicellular.
- They have membrane-bound organelles and a nucleus, making them eukaryotic.
- Protists have diverse nutritional strategies: photoautotrophy, heterotrophy, and mixotrophy.
Nutrition and Metabolism
- Photoautotrophic protists use chloroplasts for photosynthesis.
- Heterotrophic protists obtain energy by ingesting or absorbing nutrients.
- Mixotrophic protists, like Euglena, switch between autotrophy and heterotrophy.
- Some protists use phagocytosis or diffusion to obtain nutrients.
Reproduction
- Protists can reproduce asexually or sexually using meiosis and fertilization.
- Some protists, like kelp, exhibit alternation of generations, where two distinct generations are needed to complete one life cycle.
Symbiotic Relationships
- Endosymbiosis is where one organism engulfs another, leading to the formation of organelles like mitochondria and chloroplasts.
- Primary endosymbiosis occurs when a heterotrophic eukaryote consumes a bacterial cell, forming red or green algae.
- Secondary endosymbiosis occurs when a heterotrophic eukaryote consumes an alga, forming chloroplasts in other protists.
Protist Super Groups
- Protists are classified based on morphological and DNA data, including cellular walls, ribosomes, and DNA molecules.
Excavates
- Excavates have unique cytoskeleton properties, modified mitochondria, and flagella different from other organisms.
Diplomonads
- Diplomonads have modified mitochondria called microsomes with no electron transport chain.
- They have two nuclei and multiple flagella.
- They produce energy anaerobically.
- Example: Giardia lamblia, a parasite found in stagnant water, causes severe diarrhea and vomiting.
Parabasalids
- Parabasalids have a reduced number of mitochondria.
- They are anaerobic and produce hydrogen gas as a byproduct.
- Example: Trichomonas vaginalis, a sexually transmitted disease, causes burning and itching sensations in women.
Euglenozoa
- Euglenozoa have rod-shaped flagella.
- They have a kinetoplast (a single large mitochondrion with DNA).
- Example: Trypanosoma, which causes African sleeping sickness and Jacques disease, affects red blood cells, and causes fever and fatigue.
Neuglenids
- Neuglenids have a pocket at one end with one or two flagella emerging.
- They are mixotrophic, able to undergo photosynthesis and ingest other creatures.
- Example: Euglena, found in pond water, is oval-shaped with a curved excavated side.
SAR Clade
- Consists of stramenopiles, alveolates, and rhizarians, and is monophyletic, meaning it has a single common ancestor
- Originated from a common endosymbiotic event involving a red alga and a heterotrophic eukaryote
Alveolates
- Characterized by the presence of alveoli, membrane-bound air pockets that trap respiratory gases
- Include dinoflagellates, apicomplexans, and ciliates
- Dinoflagellates can cause red tides and produce toxins that can cause gastrointestinal poisoning in humans
- Apicomplexans include parasites like Plasmodium, which causes malaria, and have a complex life cycle involving multiple hosts
- Ciliates have rows of cilia and can reproduce sexually or asexually
Dinoflagellates
- Characterized by the presence of two whip-like flagella
- Found in freshwater and marine environments
- Can be photoautotrophic, heterotrophic, or mixotrophic
- Responsible for red tides and can produce toxins that can cause gastrointestinal poisoning in humans
Apicomplexans
- Include parasites like Plasmodium, which causes malaria
- Have a complex life cycle involving multiple hosts
- Can change surface proteins to evade host immune system, making vaccine development challenging
- Transmitted through mosquitoes
Ciliates
- Characterized by the presence of rows of cilia
- Can reproduce sexually or asexually through binary fission
- Have a micronucleus and a macronucleus, involved in conjugation and genetic exchange
- Paramecium is an example of a ciliate with a complex life cycle involving conjugation and nuclear exchange
Stramenopiles
- Characterized by the presence of a hairy flagellum
- Include diatoms, golden algae, brown algae, and oomycetes
- Can be photoautotrophic or heterotrophic
- Have diverse strategies for obtaining energy and nutrients
Diatoms
- Characterized by the presence of a silica test or frustule
- Found in freshwater and marine environments
- Primary producers, playing a key role in aquatic food chains
- Have a unique life cycle involving asexual reproduction through binary fission
Golden Algae
- Characterized by the presence of flagella and a yellowish pigment
- Can be photoautotrophic or mixotrophic
- Can be unicellular or colonial
- Have a complex life cycle involving sexual reproduction
Brown Algae
- Characterized by the presence of a brown pigment
- Found in marine environments
- Complex multicellular organisms that can resemble plants
- Have a unique life cycle involving alternation of generations, with a diploid sporophyte stage and a haploid gametophyte stage.
Brown Algae
- Brown algae are multicellular protists with plant-like structures, including holdfast, stipe, blades, and bladders.
- Holdfast is a root-like structure that anchors the algae to rocks or substrate, but does not absorb nutrients.
- Stipe is a stem-like structure that holds up the algae.
- Blades are leaf-like structures that hold photosynthetic cells.
- Bladders are bubble-like structures that help the algae float upright towards the water's surface.
- Brown algae undergo alternation of generations, where diploid sporophytes produce haploid spores that develop into gametophytes.
- Gametophytes produce gametes that fuse to form a zygote, which develops into a sporophyte.
- Sporophytes produce spores through meiosis, which develop into gametophytes.
- Brown algae belong to the stramenopile group, characterized by having two flagella, one smooth and one hairy.
Red Algae
- Red algae are multicellular protists that obtain their color from an abundance of phycocyanin, which reflects red light.
- Phycocyanin can also make the algae appear bluish, purple, or green.
- Some edible varieties of red algae, such as nori, are used in sushi rolls.
- Most red algae are multicellular, with a few exceptions being single-celled.
Green Algae
- Green algae are multicellular protists that live mainly in freshwater, with a few species found in oceans.
- They are characterized by their filamentous shape, such as in Spirulina and Chlorella.
- Volvox is a type of green algae studied in biology labs, characterized by its flagellated cells and multicellular structure.
- Sea lettuce (Ulva) is a type of green algae found in oceans, characterized by its flat, broad, and smooth blades.
- Caulerpa is another type of green algae found in oceans.
- Green algae are important contributors to the food chain, providing energy for organisms like fish, snails, and sea urchins.
Amoeboid Protists
- Amoeboid protists move using pseudopodia or extensions of their cytoplasm and are a diverse group.
Characteristics of Ryze Area Protists
- Ryze area is a subgroup of SAR (superphylum) protists.
- The name "Ryze" means "root" in Greek, referring to their long, thin cytoplasmic extensions used for locomotion and capturing prey.
- Examples of Ryze area protists include:
- Foraminifera, which have a protective structure called a test made of calcium carbonate with perforations that allow pseudopodia to move out.
- Radialarians, which have tests made of silica, with intricate patterns and shapes, and use pseudopodia for locomotion and capturing food.
Characteristics of Uniconta Protists
- Uniconta is a clade that includes protists, animals, and fungi.
- The common ancestor to all these organisms is still unknown to scientists.
- Examples of Uniconta protists include:
- Slime molds, which can be:
- Acellular, with many cells without plasma membranes and multiple nuclei, forming a sporangium and releasing spores.
- Cellular, with each amoeba having its own nucleus and plasma membrane, forming aggregates that migrate and feed before reproducing.
- Slime molds, which can be:
Other Amoeboid Protists
- Tubulinians (formerly Gemmaceae) are amoebas that move using cytoplasmic streaming, with lobe-like pseudopodia, and are heterotrophic, feeding on other protists, algae, and bacteria.
- Entamoebas are amoebas that can be parasites of the gastrointestinal system of mammals, including humans, and can cause severe diseases like amoebic dysentery.
Brown Algae
- Brown algae are the largest and most complex algae, consisting of multicellular species commonly called “seaweeds”.
- Giant seaweeds called kelps live in deep parts of the ocean, with a rootlike holdfast that anchors the algae, a stemlike stipe that supports leaflike blades.
- Brown algae exhibit analogous structures with plants, showing similarities between the two groups.
Alternation of Generations
- The life cycle of brown algae involves the alternation of multicellular haploid and diploid forms.
- Sporophyte (2n) produces unicellular zoospores (n) through meiosis, which develop into heteromorphic male and female multicellular gametophytes (n).
- Fertilization occurs between gametophytes, resulting in a zygote that grows into a new sporophyte.
Alveolates
- Alveolates are a group of organisms characterized by membrane-enclosed sacs (alveoli) just under the plasma membrane.
- Alveolates include Dinoflagellates, Apicomplexans, and Ciliates.
Dinoflagellates
- Dinoflagellates have two flagella twisted around the cell and are reinforced by cellulose plates.
- They are components of both marine and freshwater phytoplankton, consisting of phototrophs, mixotrophs, and heterotrophs.
- Dinoflagellates can cause Toxic “red tides”.
Apicomplexans
- Apicomplexans are parasites of animals, with some causing serious human diseases.
- They are spread as infectious cells called sporozoites, which have an apex containing a complex of organelles specialized for penetrating host cells and tissues.
- Apicomplexans have an organelle called Apicoplast, which has a circular genome similar to chloroplast genome.
- Apicoplasts' enzymes are a possible malaria drug target.
Life Cycle of Apicomplexan Plasmodium (Malaria)
- The life cycle involves two hosts: humans and Anopheles mosquitoes.
- Sporozoites (n) are injected into humans through mosquito bites, infecting liver cells and dividing into merozoites (n).
- Merozoites infect red blood cells, causing symptoms in humans.
- Some merozoites form gametocytes (n), which are then taken up by mosquitoes, where fertilization occurs, and a zygote (2n) forms.
- The zygote develops into an oocyst, releasing thousands of sporozoites (n) via meiosis, which migrate to the mosquito's salivary gland.
Ciliates
- Ciliates use cilia to move and feed, and have two types of nuclei: large macronuclei and small micronuclei.
- Genetic variation in ciliates results from conjugation, where two individuals exchange haploid micronuclei.
Protists as Symbionts
- Protist symbionts can benefit their hosts, such as dinoflagellates that nourish coral polyps, which build reefs.
- Wood-digesting protists can digest cellulose in the gut of termites.
- Some protists are parasitic, causing diseases in hosts, such as:
- Plasmodium, which causes malaria.
- Pfiesteria shumwayae, a dinoflagellate that causes fish kills (red tides).
- Phytophthora ramorum, which causes sudden oak death.
- P.infestans, which causes potato blight, contributing to the Irish famine of the 19th century.
Protists as Producers
- Many protists are important producers that obtain energy from the sun.
- In aquatic environments, photosynthetic protists and prokaryotes are the main producers, upon which other organisms depend for food.
- Photosynthetic protists in aquatic environments are limited by nutrients.
- Adding limiting nutrients can cause protist populations to explode, such as when fertilizers used in fields are washed into oceans.
- An increase in sea surface temperature has led to a decline in the biomass of photosynthetic protists.
- The growth of phytoplankton communities relies on nutrients delivered from the ocean bottom through the process of upwelling.
- Warm surface water acts as a barrier to upwelling, affecting phytoplankton growth.
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Description
Learn about apicomplexans, parasites that cause serious human diseases, their life cycle, and how they spread through hosts. Includes information on Plasmodium and malaria.