Biology: Protists

  1. Protists are in classified in what Domain and Kingdom?
    Domai Eukarya and Kingdom Protista
  2. What is unique about protist Giardia?
    • Has two nuclei but no mitochondria
    • -suggests that indeed a nucleated cell preceded the acquisition of mitochondria.
  3. Most protists are primarily unicellular.
    A. True
    B. False
    True! very few can be multi-cellular
  4. Most protist produce asexually.
    A. True
    B. False
    True! However, sexual reproduction can occur if the environment becomes stressful.
  5. Protists have 3 different ways they can reproduce.
    • 1. Asexual - most common
    • 2. Sexual - only during stressful environments
    • 3. Cyst formation - only during stressful environments
  6. When and how does a protist form a cyst?
    • Another common way for a protist to survive hard times is cyst formation.
    • A cyst is a dormant cell with a resistant outer covering.
    • A cyst can help a free-living protist over winter or a parasite survive the digestive juices of its host.
    • Some protists pass from host to host when food and water are contaminated by feces that contain cysts.
  7. Being aquatic, protists that are photosynthesizers give off oxygen and function as producers in freshwater and saltwater ecosystems.
    A. True
    B. False
    • True
    • Protists are part of plankton organisms that are suspended in the water and serve as food for heterotrophic protists and animals.
  8. Protists enter symbiotic relationships ranging from parasitism to mutualism.
    A. True
    B. False
    • True
    • Ex: Coral reef formation is greatly aided by the presence of a symbiotic photosynthetic protist that lives in the tissues of coral animals.
  9. Evolution of Protists:
    Why can't protists be classified with plants?
    Because not even the multi-cellular photosynthesizers cannot protect the gametes and zygote from desiccation.
  10. Evolution of Protists:
    Why can't protists be classified with animals?
    Because the heterotrophic ones do not undergo embryonic development.
  11. Evolution of Protists:
    Why can't protists be classified with Fungi?
    Because Protists do not have chitin in their cell wall.
  12. Which Phylums in Kingdom Protista are Photoautotrophs?
    Hint: There are 6.
    • 1. Phylum Chlorophyta: Green Algae
    • 2. Phylum Rhodophyta: Red Algae
    • 3. Phylum Phaeophyta: Brown Algae
    • 4. Phylum Bacillariophyta: Diatoms, golden-brown algae
    • 5. Phylum Pyrrophyta: Dinoflagellates
    • 6. Phylum Euglenophyta: Euglenoids.
  13. Phylum Chlorophyta: Green Algae

    General Info
    • -have both chlorophyll a and chlorophyll b.
    • -have cellulose cell walls
    • -store carbohydrates as starch

    Can be unicellular, filamentous, or multicellular.

    *Biologists have hypothesized that Green Algae are most closely related to plants.
  14. Phylum Chlorophyta: Green Algae

    *Chlamydomonas, a Unicellular Green Alga**
    • Photoautotrophs
    • has a definite cell wall
    • contains a pyrenoid, which is a dense body where starch is synthesized
    • 2 long, whiplike flagellas
    • chloroplast contains a red-pigmented eyespot (stigma) which is sensitive to light and helps bring the organism into the light, where photosynthesis can occur
    • often reproduces asexually as many as 16 daughter cells within the parent wall
    • -can also reproduce sexually when growth condition become unfavorable.
    • -gametes of two different mating types come into contact and join to form a zygote
    • -A heavy wall forms around the zygote, and it becomes a resist zygospore that undergoes a period of dormancy.
    • -When a zygote germinates, it produces four zoospores by meiosis
    • -A spore is a reproductive cell that develops into a new organism without the need to fuse with another reproductive cell.
    • -Zoospores, which are flagellated spores, are typical of aquatic species.

    • SUMMARY:
  15. Phylum Chlorophyta: Green Algae

    **Spirogyra, a Filamentous Green Algae**
    • Photoautotrophs
    • Unbranched, filamentous green algae
    • Found in green masses on the surfaces of ponds and streams
    • sexual reproduction where it undergoes conjugation
    • Conjugation - temporary union during which the cells exchange genetic material, forming diploid zygotes.
    • - These zygotes survive the winter, and in the spring they undergo meiosis to produce new haploid filaments.
  16. Phylum Chlorophyta: Green Algae

    • Multicellular green algae
    • Commonly called sea lettuce
  17. Phylum Chlorophyta: Green Algae

    • live in freshwater lakes and ponds
    • called stonewarts because they have heavily calcified cell walls.

    • Example: Chara
    • -forms a cell plate during cell division and has multicellular sex organs
    • -zygote is retained for a time in the female sex organ
    • *DNA analysis suggest that among green algae, stoneworts are the most closely related to plants.
  18. Phylum Chlorophyta: Green Algae

    **Volvox, a Colonial Green Alga**
    • Colony-loose association of independent cells in which some cells maybe specialized for reproduction.
    • Flagella beat in a coordinated fashion
  19. Phylum Rhodophyta: Red Algae
    • multicellular or can have filamentous branches
    • gametes do not contain flagella
    • mainly live in warmer seawater, shallow or deep waters

    • Main species have commercial importance:
    • Agar - gelatin-like product primarily from the algae Gelidium and Gracilaria.
    • -agar used in making capsules for vitamins/drugs, material for dental impression, base for cosmetics
    • -In the lab, agar is used for gel electrophoresis.

    Example: Chondrus crispus -emulsifying agent for the production of chocolate and cosmetics.
  20. Phylum Phaeophyta: Brown Algae
    • multicellular
    • flagellated sperm cells
    • contain chlorophyll a & c
    • contains carotenoid pigment called fucoxanthin that gives them that color
    • reserve food is a carbohydrate called laminarin
    • found along the rocky coasts
    • They dry out slowly because their cell walls contain a mucilaginous water-retaining material.
    • *Most brown algae have the alternation of generations life cycle, but some species of Fucus are unique in that meiosis produces gametes and the adult is always diploid, as in animals.

    • Some brown algae are giant seaweeds, or kelps - grows along the shoreline
    • Other examples: Macrocystis, Laminaria, Fucus, kelp
  21. Phylum Bacillariophyta: Diatoms
    • most numerous unicellular algae in the oceans
    • plentiful in freshwater
    • have tests (shells) that fit together like a box with a lid. The tests consist of silica (SiO2) --a common ingredient in glass
    • reproduce asexually and sexually
    • significant producers of food and oxygen in aquatic ecosystems because of their sheer abundance.
  22. Phylum Pyrrophyta: Dinoflagellates
    • unicellular
    • cells usually bounded by protective cellulose plates impregnanted with silicates
    • typically have 2 flagella(one lies longitudinal, other transverse)
    • Chloroplasts vary in color because in addition to chlorophyll a & c, dinoflagellates also contain carotenoids.
    • part of the phytoplankton
    • usually reproduce asexually
    • Like diatoms, one of the most important producers in marine environments.
    • Gonyaulax, an example, contains a red pigment that is responsible for "red tides"
  23. Phylum Euglenophyta: Euglenoids
    • unicellular
    • live in freshwater
    • some have chloroplasts, other do not
    • -those that lack chloroplasts ingest or absorb their food.
    • have two flagella---one called a tinsel flagellum because it has hairs on it
    • near base of flagella---is an eyespot that permits phototaxis (ability to move in response to light)
    • Instead of a cellulose wall, they have thin, protein strips called pellicles that wrap over their cell membranes.
    • reproduce by longitudinal cell division
    • sexual reproduction is not known to occur.
  24. Phylum Zoomastigophora: Zooflagellates
    • colorless
    • lack plastids
    • heterotropic
    • has one flagella
    • most are symbiotic
    • many are parasitic
    • **well known for causing various diseases in humans
    • *Trypanosoma brucei a cause of African sleeping sickness
    • *Trypanosomes, trasmitted by the bite of a tsetse fly
    • * WBC accumulate around the blood vessels leading to the brain and cut of circulation, causes an inadequate supply of oxygen
    • *Giardia lamblia, whose cysts are transmitted by way of contaminated water attaches to the human intestinal wall and causes severe diarrhea
    • *Trichomonas vaginalis, sexually trasmitted, infects vagina, urethra of women, and prostate/seminal vesicles, and urethra of men.
  25. Protozoans
    • -unicellular eukaryote
    • *are considered "animal-like"
    • includes both photosynthetic and heterotrophic organisms. (mainly heterotrophic)
    • some heterotrophic organisms ingest their food by endocytosis
    • usually has some form of locomotion--> flagella, pseudopods, cilia.
    • consume living cells (predatory, or parasitic), or dead organic matter
  26. What is a pseudopod?
    • Pseudopods are processes that form when cystoplasm streams forwards in a particular direction.
    • Protists that have pseudopods usually live in aquatic environments
    • -oceans, freshwater, lakes, ponds
  27. Protists with Pseudopods:

    Protozoa: Phylum Rhizopoda: amoeboids
    • move and ingest their food by pseudopods
    • absorb food by phagocytosis
    • Digestion occurs within a food vacuole.

    • Examples:
    • Amoeba proteus: have contractile vacuoles where excess water from the cytoplasm collects before the vacuole appears to "contract" releasing water through a temporary opening in the plasma membrane
    • Entamoeba histolytica: parasitic amoeboid: lives in the human intestine and causes amoebic dysentery.
  28. Protists with Pseudopods

    Protozoa: Phylum Foraminifera: Foraminiferans
    Phylum Actinopoda: Radiolarians
    • have a skeleton called test, made up of calcium carbonate
    • are abundant in the ocean
    • many ancient marine sediments consisting of certain foram tests are good indicators of underlying oil deposits.
  29. Phylum Ciliophora: Ciliates

    Protozoa: Example: Paramecium
    • *Most complex of protozoans
    • move by cilia
    • is a single cell that has specialized regions to carry out various functions
    • - mouths
    • -anal pores
    • -contractile vacuoles for water balance
    • -two kinds of nuclei (one large macronucleus, and several micronuclei)
    • -trichocysts-discharge long barbed threads that are useful for defense and capturing prey
    • Most ciliates are holozoic.
    • Soluble nutrients are absorbed by the cytoplasm
    • -can produce asexually : ciliates divide by transverse binary fission.
    • -can reproduce sexually by conjugation
  30. Phylum Apicomplexa : Sporozoans
    • non-motile parasites
    • forms spores
    • Examples: Pneumoocystis carinii : types of pneumonia primarily seen in AIDS patients
    • Plasmodium vivax- cause of one type of malaria
  31. Which protists are considered to be "fungus-like"?
    • cellular slime molds
    • plasmodial slime molds
    • oomycota

    **were once considered fungi, however, unlike fungus, all have flagellated cells
  32. Fungus Like:

    Phylum Myxomycota: plasmodial slime molds
    • grow as a single, spreading mass (or plasmodium)
    • feeds on decaying vegetation
    • when food becomes unavailable, it develops sporangium (reproductive structure that produces spores)
    • Spores release a haploid flagellated cell, haploid amoeboid cell, which fuse to form a diploid zygote.
    • Diploid cell grows into a multi-nucleated plasmodium.
  33. Fungus-like Protists:

    **Phylum Acrasiomycota: Cellular Slime Molds**
    • exhibit both fungus-like & protozoa-like characteristics during their life cycle
    • Spores germinate into amoebas which feed on bacteria
    • When food sources are depleted, the amoebas aggregate into a single unit (pseudoplasmodium)
    • The pseudoplasmodium stage is temporary and eventually gives rise to a fruiting body, in which sporangia produce spores
    • When conditions become favorable again, spores germinate released haploid amoeboid cells, and the asexual cycle begins again
    • Energy used to asexual reproduction is cAMP (cyclic AMP)
    • Sexual cycle is known to occur under very moist conditions.
  34. Fungus-Like Protists

    Phylum Oomycota: water molds
    • live in water molds, mildews
    • either parasites or saprobes

    • Similarities/Differences with Fungus:
    • -have a filamentous (hyphae) body like fungus, (however, water molds lack septa, or cross walls, which many true fungi have)
    • - cell wall is largely composed of cellulose,whereas fungi have cell walls of chitin
    • -life cycle differs from Fungus

    • Asexual reproduction - produce motile spores, (which are flagellated)
    • -adult is diploid (Haploid in Fungus)
    • -meiosis produces gametes

    *Phylum refers to the enlarged tips called oogonia where eggs are produced.
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Biology: Protists
Biology: Protists