CH 28: Protists Flashcards
What are protists?
Eukaryotes that are not classified in the plant, animal, or fungal kingdom
What are the common characteristics of of protists?
- Most abundant in moist habitats
- Most of them are microscopic in size
- Have a membrane bound nucleus (eukaryote)
How can protists be classified?
Ecological Role
Habitat
Motility
How are protists classified by ecological role?
Three major groups:
- Algae–generally photoautotrophic
- Protozoa–heterotrophic
- Fungus-like–resemble fungi in body form and absorptive nutrition
How are protists classified by habitat?
Particularly common and diverse in oceans, lakes, wetlands and rivers
- Plankton–swimming or floating (occur primarily as single cells, colonies or short filaments)
- Periphyton-attached by mucilage to underwater surfaces
- Produce multicellular bodies •Seaweeds or macroalgae
What are the types of plantkton?
- Phytoplankton–photosynthetic
- Protozoan plankton –heterotrophic
How are protists classified by motility?
Flagella, Cilia, Pseudopodia
Swim using eukaryotic flagella
Cilia –shorter and more abundant than flagella
Amoeboid movement –using pseudopodia
Are Protists a monophyletic group?
No. Was a single kingdom at one time.
What are is the Eukaryotic Supergroup Excavata?
Related to some of Earth’s earliest eukaryotes
- Named for a feeding groove “excavated” into the cells
- Food particles are taken into cells by phagotrophy
- Endocytosis
What is the example of Supergroup excavata we went over in class?
Euglenozoa
- Protein strips under plasma membrane allow crawling
- Some are heterotrophic, but Euglena is photosynthetic
What are Kinetoplastids and which supergroup do you find them in?
Named for unusually large mass of DNA (kinetoplast) in a single large mitochondrion Found in Supergroup Excavata
What is the Eukaryotic Supergroup Land Plants and Relatives?
Supergroup that includes land plants also encompasses several algal phyla Kingdom Plantae (land plants) evolved from green algal ancestors
- Phylum Chlorophyta–green algae
- Phylum Rhodophyta–red algae
Why are algae different colors?
Algae reside at different depths which determines their color because they absorb different wavelengths of light at different depths
What are Green Algae and what Supergroup are they a part of?
Phylum Chlorophyta
- Diverse structural types
- Occur in fresh waters, the ocean, and on land
- Most are photosynthetic
- Cells contain same type of plastids and photosynthetic pigments as in land plants
What are Red Algae and what Supergroup are they a part of?
Most are multicellular marine macroalgae
- Red appearance due to distinctive photosynthetic pigments (live at deep depths)
- Lack flagella
How did Red Algae develop primary plastids?
Primary Endosymbiosis
- Primary plastid: enclosing envelope made of two membranes
- Heterotrophic host cells captured cyanobacterial cells via phagocytosis –but did not digest them
- Endosymbioticcyanobacteria provided host cells with photosynthetic capacity and other useful biochemical pathways •Eventually evolved into primary plastids
What is primary endosymbiosis?
Eukaryote ingests a prokaryote–but does not digest them
Where did secondary plastids originate?
Secondary plastids derived from a photosynthetic eukaryote,likely a red alga
- Originate from secondary endosymbiosis
- Eukaryote consuming another Eukaryote
- Eukaryotic host cell ingests and retains another type of eukaryotic cell that already has one or more primary plastids, such as a red or green alga
How many membrane envelopes does a primary plastid have? Secondary Plastid?
Primary Plastid: Two envelopes
Secondary Plastid: Three envelopes
What Phyla are contained within Eukaryotic Supergroup Alveolata?
Alveolata named for saclike membranous vesicles (alveoli) present in cell
Ciliophora
•Ciliates –conjugation
Apicomplexa
- Medically important parasites
- Plasmodium
Dinozoa
- Dinoflagellates–some photosynthetic, others not
- Red tide and mutualistic relationship with coral
What phyla are dinoflagellates a part of? What are some of their characteristics?
Supergroup: Alveolata; Phylum: Dinozoa
- 1/2 of dinoflagellatesare heterotrophic
- 1/2 possess photosynthetic plastids that originated by secondary or even tertiary endosymbiosis
- Tertiary plastids are obtained by tertiary endosymbiosis
- Endosybiosis of organism with secondary plastids
What is the Eukaryotic Supergroup Stramenopila?
Wide range of algae, protozoa, and fungus-like protists
- Produce flagellate cells at some point
- Named for distinctive strawlike hairs on the surface of flagella
- Heterotrophic or photosynthetic
- Plastids from secondary endosymbiosis with red algae
What is the Eukaryotic Supergroup Amoebozoa?
Many types of amoebae
•Move using pseudopodia
What is the model organism for Amoebozoa?
Dictyosteliumdiscoideum, slime mold
- Model organism for understanding movement, cell communication, and development.
- In response to starvation, single amoebae aggregate into a multicellular “slug” that develops into a stalked structure containing spores
- Spores pop out and produce new amoebae
What is the Supergroup Opisthokonta?
Includes animal and fungal kingdoms and related protists
- Named for single posterior flagellum on swimming cells
- Contains protists most closely related to humans
What Protists are a part of Eukaryotic Supergroup Opisthokonta?
Choanoflagellate protists
- Feature distinctive collar surrounding flagella
- These are the modern protists most related to the common ancestor of animals
What are the Nutritional and Defensive Adaptations of Protists?
Phagotrophy–heterotrophs that ingest particles
Osmotrophy–heterotrophs that rely on uptake of small organic molecules
Photoautotrophy–photosynthetic
Mixotrophy–able to use autotrophy and phagotrophy or osmotrophy depending on conditions
What are the characteristics of algal protists?
Variety of pigments
- Adapt photosystems to capture more light
- Water absorbs the longer red and yellow wavelengths more than the shorter blue and green wavelengths
- Accessory pigments absorb light and transfer it to chlorophyll a Variety of types of food storage molecules
- Starch, polysacchrides, and oil
What defense mechanisms do Protists exhibit?
Slimy mucilage or cell walls defend against herbivores and pathogens
•Calcium carbonate, silica, iron, manganese armor
Trichocysts–spear-shaped projectiles to discourage herbivores
Bioluminescence–startles herbivores
Toxins–inhibit animal physiology
What Reproductive Adaptations do Protists exhibit?
Asexual Reproduction Sexual Reproduction
-Zygotic and Sporic Life Cycles
What are the features of protist asexual reproduction?
All protists can reproduce asexually
- Many produce cysts with thick, protective walls that remain dormant in bad conditions (cause of dinoflagellate blooms)
- Many protozoan pathogens spread from one host to another via cysts
Where did Eukaryotic sexual reproduction with gametes and zygotes arise from?
It arose from Protists resulting in diverse genotypes
Describe the Zygotic Life Cycle.
What is the sporic lifecycle?
Many multicellular green and brown seaweeds
Also known as alternation of generations
Two types of multicellular organisms
•Haploid gametophyte produces gametes
•Diploid sporophyte produces spores by meiosis
Describe the steps of the alternation of generations (sporic lifecycle).
