Protozoans Flashcards
(125 cards)
Protozoans
- Unicellular, eukaryotes without a collagen and chitinous cell walls
- animal like organisms
- mostly heterotrophs
- hypothesized that flagellates protozoans are animal ancestors
Do protozoans go under photosynthesis
Not in the primitive condition
Do protozoans develop from the blastula embryonic stage like animals?
No
How do protozoans live and obtain food
Most are free living organisms that obtain food from decaying organic materials or feed on bacteria and smaller eukaryotes
-some are parasites/ pathogens
How many species of protozoans are identified
40000
In protozoans the single cell functions as a ___
Whole organism
-therefore they lack specialized organelles for respiration, digestion and excretion
Size of protozoans
Microscopic
-5-250 nano meters or smaller
What are 3 ways protozoans can live
Free living
Parasitic (cause disease)
Commensal (association with each other)
Where do protozoans live
Inhabit moist environments
Surface covering of protozoans
Plasmalemma (cell membrane)
-differentiated into ectoplasm (outer clear gelatinous region) and endoplasm (inner fluid region containing cell organelles)
Unique organelles of protozoans that are not found in most metazoans
- Contractile vacuole
- Spongiome
- Trichocyst
- Toxicyst
Contractile vacuole
Used for osmoregulation (release water from the cytoplasm, maintaining concentration and osmotic gradient in cells)
Spongiome
Collection of vesicles and tubules for fluid collection storage in the cytoplasm
-connects contractile vacuole for expelling water out of the cell
Trichocyst
Elongated capsule-like filament released in response to mechanical or chemical stimulus. Protect against predation and aid anchorage during feeding.
Developed in membrane bound vesicles in the cytoplasm, lie around the peripheral of the cell and released to the surface as extrusomes
Toxicyst
Toxins for paralyzing prey and initiating digestion
Non functional and functional vacuole in cell osmoregulation
Non functional: allows excess fluid into a cell, resulting in increased cell volume and reduced cytoplasmic solute concentration
Functional: allows water influx but loses both water and solute, decreasing cytoplasmic solute
Functional: regulates influx and efflux of water, maintaining cell volume and cytoplasmic solute concentration
Extrusomes
For injecting prey with mucus, toxins (Toxicyst) when released
Stimulated in response to feeding (catching prey) or defending or attaching to substrate
Common locomotor organelles utilized by free living protozoans:
Cilia (paramecium)
Flagella (euglena)
Pseudopodia (amoeba)- flowing extensions of cytoplasm
Cilia
-short, hair like structures found on the surfaces of protozoa called ciliates (phylum ciliophora)
-cylindrical in shape and arise from basal body called a kinetophore
-can be distributed more or less uniformly all over cell surface, in rows or patches or grouped in tufts (cirri-walk or jump on solid surfaces)
-used for swimming and allow ciliated to move smoothly through water or even jump
-capable of whip like logon coordination by microtubule arranged in cell membrane
-
Cilia cross section anatomy
Inside each cilium contains long fibers called microtubules made up of proteins known as tubulin.
Each cilium is surrounded by the cell membrane and is supported by a cytoskeleton of microtubules arranged in a 9 doublet +2 pattern
The whole microtubules complex containing the 9 doublet +2 central sheath is called an axoneme
Flagella
- long, while like structures found on the surfaces of many protozoans
- typically for locomotion and feeding
- shared similar cross section to cilia.
How does flagella differ from cilia
- bearing hairlike projections on its surface (mastigonemes) which increase surface area and enabling greater propelling through water.
- flagella usually fewer and longer than cilia
Pseudopodia
(False feet)
- characteristic of the amoeba group of protozoans
- important in locomotion and feeding whereby protozoan flows in its intended direction by cytoplasmic steaming
- movement of Pseudopodia is mediated by a controlled transition of gelatinous ectoplasm (gel) and fluid endoplasm (sol)
- Pseudopodia vary in size and shape but are like cilia and flagella are surrounded by the cell membrane and often supported by microtubules (not 9+2)
Pseudopodia variant’s
Lobopodia: broad, rounded lip and finger like
Filopodia: threadlike, slender and often branched
Reticulopodia: forms highly reticulated (branched) of extremely thin filaments
Anxiopoda: thin rods composed of microtubules