Unicellular Eukaryotes Flashcards
1
Q
Why are they interesting?
A
- Diverse and beautiful
- Unicellular but complete
- Component of plankton
- Cause many diseases
2
Q
What are the disadvantages of being unicellular?
A
- Size is limited
Less things to eat, more things can eat you
- Shorter life span
Any insult will kill you
Less time for reproduction
- No division of labour
Multicellular organisms have differentiated cells with different
functions that work together
3
Q
Why is size limited?
A
- Surface/volume ratio decreases as cells get bigger
- Single cell depends on food/nutrients/waste/water to diffuse across plasma membrane
- Internal region of cell becomes too big to be supported by the plasma membrane
4
Q
What are the advantages of being unicellular?
A
- Rapid reproduction (asexual or sexual)
- Minimal resources required
Successful group (over 64,000 species of protozoans have
been named and estimates are that up to 250,000
protozoan species exist)
5
Q
What are unicellular eukaryotes?
A
- Complete organisms
Carry out all of life’s activities within a single cell - Mostly motile
- Require moisture
- Cause many disease in humans and other animals
6
Q
What are the modes of locomotion?
A
- Flagella (whiplike organelle of locomotion)
- Cilia
A hairlike organelle found on many animal cells
Cilia may be used in moving particles along the cell surface,
or, in ciliated unicellular forms, for locomotion - Pseudopodia
A temporary cytoplasmic protrusion extended out from an
ameboid cell
Serves for locomotion or engulfing food
7
Q
What is undulipodia?
A
- Cilia and flagella are morphologically the same
- Made up of nine pairs of microtubules arranged around a central pair
- Cilia are generally numerous, and propel water parallel to the cell surface
- Flagella propels water parallel to the flagellum axis
8
Q
What is the Pseudopodia?
A
- Temporary projections of cell membrane
- Used for locomotion and phagocytosis
- Cytoplasm is not homogeneous. Consist of:
Ectoplasm semi-solid outer layer
Endoplasm inner fluid - Endoplasm flows forward into pseudopod and solidifies into ectoplasm
9
Q
What is Taxonomy?
A
- Traditionally classified by body type
- Flagellates (one or more flagella to propel cell)
- Ciliates (numerous cilia covering cell membrane)
- Amoebas
Irregular shape
Travel using pseudopodia
Plasma membrane can be covered with a test or shell
10
Q
What is there nutrition and digestion?
A
- Unicellular eukaryotes can be autotrophs, heterotrophs or both
Autotrophs (Self-feeding from environment. Plants, algae,
many bacteria, unicellular eukaryotes)
Heterotrophs (Consumes other life. Animals, fungi, many
bacteria, unicellular eukaryotes) - Heterotrophs can be:
Holozoic feeders: ingest visible particles of food
Saprozoic feeders: ingest food in a soluble form (soluble food
moves directly across membrane) - Cytostome
The cell mouth in many unicellular eukaryotes
Site of phagocytosis
Occurs in most ciliates, many flagellates - Cytoproct
Site on a unicellular eukaryote where undigestible matter is
expelled
Occurs in many ciliates
11
Q
What is the Nutrition and Digestion (Phagocytosis)?
A
- Plasma membrane folds around the food particle
- Membrane is pinched off at the surface
- The food particle is in an intracellular membrane-bound vesicle the food vacuole or phagosome
- Lysosomes, small vesicles containing digestive enzymes, fuse with the food vacuole and pour their contents into it
- Digestion begins
12
Q
What is symbiosis?
A
- Many protozoans are symbiotic
- Symbiosis
The living together of two different species in an intimate
relationship
At least one species benefits; the other species may benefit - The relationship may be:
Mutualism (both partners benefit)
Commensalistic (one partner benefits, no effect on the other)
Parasitic (one partner benefits at the expense of the other)
13
Q
What is their reproduction?
A
- All reproduce asexually (doesn’t involve the formation of gametes)
- Some reproduce sexually as well (fusion of two specialized cells, or gametes)
14
Q
What is the reproduction in Paramecium sp.?
A
- Binary fission
Form of asexual reproduction - Conjugation
Form of sexual reproduction
Temporary union of two ciliate protozoa for the purpose of
exchanging chromosomal material - They are multinucleate (at least one micronucleus and macronucleus)
15
Q
What is a macronucleus?
A
- Metabolism, synthesis, development
- Paramecium cannot survive without macronucleus
- Macronuclei divide amitotically
