Unicellular Eukaryotes Flashcards
Why are they interesting?
- Diverse and beautiful
- Unicellular but complete
- Component of plankton
- Cause many diseases
What are the disadvantages of being unicellular?
- 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 togetherWhy is size limited?
- 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
What are the advantages of being unicellular?
- 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)
What are unicellular eukaryotes?
- 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
What are the modes of locomotion?
- 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
What is undulipodia?
- 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
What is the Pseudopodia?
- 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
What is Taxonomy?
- 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
What is there nutrition and digestion?
- 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
What is the Nutrition and Digestion (Phagocytosis)?
- 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
What is symbiosis?
- 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)
What is their reproduction?
- All reproduce asexually (doesn’t involve the formation of gametes)
- Some reproduce sexually as well (fusion of two specialized cells, or gametes)
What is the reproduction in Paramecium sp.?
- 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)
What is a macronucleus?
- Metabolism, synthesis, development
- Paramecium cannot survive without macronucleus
- Macronuclei divide amitotically
What is a micronucleus?
- Sexual reproduction
- Paramecium cannot reproduce without the micronucleus
- Micronuclei divide mitotically
Explain conjugation in Paramecium sp.
Temporary union of two individuals to exchange chromosomal material
A) Two Paramecium individuals come into contact on their oral surface
B) The micronuclei divide by meiosis to produce four haploid micronuclei. Macronuclei degenerate
C) Three micronuclei degenerate; the remaining micronucleus divides to form male and female pronuclei.
D) Male pronuclei are exchanged between conjugants
E) Male and female pronuclei fuse to make a diploid nucleus, and individuals separate
F) Three sets of mitotic divisions produce eight micronuclei; four of these become macronuclei while three degenerate
G) The remaining micronucleus divides twice as does the cell, producing four daughter cells
What is reproduction in Apicomplexa?
- Apicomplexa is a phylum of parasitic protists
- All endoparasites
- Hosts include many animal phyla
- No obvious, unifying, locomotor organelles
- Life cycle includes both asexual and sexual reproduction
- Sometimes use an intermediate host
What is the Plasmodium reproduction?
- Includes both asexual and sexual stages
- Requires two hosts
Definitive host (insect)
Intermediate host (vertebrate)
What is a definitive host?
- The host in which sexual reproduction of a symbiont occurs
- If no sexual reproduction, the host where symbiont matures and reproduces
What is an intermediate host?
A host in which some development of a symbiont occurs, but in which maturation and sexual reproduction do not occur
Schizogony vs Sporogony
- Schizogony (multiple fission)
sporozoite (n) leads to many merozoites (n) - Sporogony (special case of schizogony)
zygote (2n) leads to many sporozoites (n)
