8. Unicellular Eukaryotes Flashcards
Protozoa
Animal-like unicellular organisms
- Paraphyletic
Disadvantage of being unicellular
- Limited size
- Shorter life span: Prone to external damage / Shorter time for reproduction
- No division of labor
Uncellular Eukaryotes
- Complete organisms
- Mostly motile
- Require moisture
- Cause diseases in many animals
Modes of Locomotion in Unicellular Eukaryotes
- Flagella
- Cilia
- Pseudopodia
Undulipodia
- Flagella & Cilia
- Made up of microtubules
- Flagella propels water parallel to flagellum axis
- Cilia propels water parallel to the cell surface
Pseudopodia
- Temporary projection of cell membrane
- Used for locomotion and phagocytosis
- Non-homogeneous cytoplasm
Endoplasm (Locomotion)
- Inner fluid of cytoplasm in pseudopodia
Ectoplasm (Locomotion)
- Outer semi-solid layer of cytoplasm in pseudopodia
Protozoan Taxonomy
Traditionally classified by body type (Not necessarily monophyletic)
- Flagellates
- Ciliates
- Amoebas
Amoebas
- Irregular shape
- Travel using pseudopodia
- Plasma membrane can be covered with a ‘test’ or shell
- Testate vs naked amoeba
- Shell can be from sand grains, calcium, or silica
Foraminifera
Testate amoeboid protozoans
Nutrition / Digestion of Unicellular Eukaryotes
Autotroph or Heterotrophs
- Holozoic : Ingest food and digest (Phagocytosis)
- Saprozoic : Ingest food in soluble form
Phagocytosis Process
- Plasma membrane folds around food
- Membrane is pinched off at the surface
- The food particle is in an intracellular membrane-bound vesicle - Food vacuole or phagosome
- Lysosomes fuse with the food vacuole and pour their contents into it
Cytostome
Cell mouth
- Site of phagocytosis
- Most ciliates, Many Flagellates
Amoebas don’t have - Phagocytosis occurs anywhere
Cytoproct
Site on Unicellular Eukaryotes where undigestible matter is expelled
- Occurs in many ciliates
Symbiosis
Mutualism - Both benefit
Commensalistic - One Partner benefits, neutral to the other
Parasitic - One partner benefits at the expense of the other
Reproduction of protozoans
All do asexual reproduction
Some do sexual as well
Types of Asexual Reproduction
- Binary Fission
- Multiple Fission (Schizogony)
- Common among Apicomplexa and Some Amoebas
- Sporogony - Spore formation - Budding
- Gemmulation
- Fragmentation
- Multicellular
Conjugation
Form of sexual reproduction
- Temporary union of two ciliate protozoa for the purpose of exchanging chromosomal material
- Exchanging plasmids too
Micronucleus
Sexual reproduction
- Mitotic division
Macronucleus
Metabolism, synthesis, development
- Amitotic division
- Replication but randomly dispersed
Binary Fission in Paramecium sp.
- Micronucleus begins mitosis
- Macronucleus begins elongation . Bud appears on cytosome
- Micronucleus divides. Macronucleus divides into two pieces. New gullet forms. Two new contractile vacuoles appear
- Division of cell body completed
Conjugation in Paramecium sp.
- Two individuals contact
- Micronuclei divide by meiosis to produce four haploid micronuclei, Macronuclei degenerate
- Micronuclei degenerate except one. Micronucleus divides to form male and female pronuclei
- Two individuals exchange male pronuclei
- Two pronuclei is fused to make diploid nucleus and the two individuals separate
- Three mitotic division form eight micronuclei; four become macronuclei and three degeerate
- Micronucleus divides twice forming four daughter cells
Apicomplexa
Phylum of parasitic protists
- Endoparasites
- Hosts include many animal phyla
- No obvious, unifying locomotor organelles
- Sexual and asexual reproduction
- Sometimes use intermediate hosts
Plasmodium falciparum
Malaria-causing parasites
- Definitive host - insect
- Intermediate host - Vertebrate
Definitive host
Where sexual reproduction occurs
- If no sexual reproduction, where symbiont matures and reproduces
Intermediate host
- Some development of a symbiont
- Maturation and sexual reproduction do not occur
Asexual Cycle of Plasmodium
- Sporozoites injected and migrate to liver.
- Sporozoites undergoes schizogony
- Merozoites released
- Merozoites enter red blood cells and undergo schizogony
- Macrogametocyte (female) and microgametocyte(male) forms / Trophozoite forms
- Gametocytes transmitted to insect. / Merozoites released from Trophozoite
Sexual Cycle of Plasmodium
- Gametocytes are ingested by insect
- Ookinete(zygote) forms through fertilization
- Oocytes develop beneath stomach lining
- Sporogony occurs
- Sporozoites develop in oocysts and are released into salivary glands.
Schizogony
Multiple fission
- sporozoite to merozoites
- n to n
Sporogony
Special case of schizogony
- zygote to spoeozoites
- 2n to n
