lecture 17: protists Flashcards
Morphology of protists?
Many unicellular, some colonial, some multicellular
Size of cells of protists?
Large range in size, some large and complex and some as small as prokaryotes
Reproduction of protists?
Asexual or sexual: most = asexual routinely and sexual only intermittently
Are there any unique characteristics to protists?
No
Where do you find protists?
Common feature: tend to live in environments where they are surrounded by water
What are protists?
All eukaryotes EXCEPT land plants, fungi and animals —> very diverse group
- No unique trait in found in protists
- Some are more related to plants/animals than to other protist groups
- Protists = paraphyletic: represent some, but not all of the descendants of a single common ancestor
3 informal protist groups?
- Protozoa: animal-like —> energy source, no cell wall, motile
- Algae: plant-like —> photosynthetic cell wall, photoautotroph, not really motile
- Slime- or Water-Molds: fungus-like —> decomposers
Examples of protists
Desmids, diatoms, amoebae, ciliates (stentor and paramecium), euglenids, volvox
2 modes of nutrition and description
CHEMOHETEROTROPHS: (protozoa)
1. Ingestive nutrition: organic material are taken into cell by endocytosis & digested with lysosomes (broken down in food vacuoles) —> possible in animal-like protists that lack a cell wall
2. Absorptive nutrition: absorb organic nutrients directly form environment across plasma membrane
PHOTOAUTOTROPH: (algae)
3. Photosynthesis: CO2 fixed into organic molecules using light energy
3 modes of locomotion
Move to find food/light
- Pseudopodia (amoeba) —> amoeboid motion
- Cilia (ciliates) —> swimming
- Flagella —> swimming
Describe life cycles of protists
- Very diverse & complicated
- Asexual and sexual loops
- Can be dominated by haploid or diploid cells
Photosynthetic pigments in photosynthetic protists
Very diverse —> Lead to diverse properties
Explain possibilities of evolution of photosynthesis in algae (and some protists) + accepted hypothesis
Only some protists are photosynthetic
1. Photosynthesis could have evolved independently several times
2. Several groups could have lost ability to do photosynthesis
3. SECONDARY ENDOSYMBIOSIS: photosynthesis transferred to many unrelated groups by horizontal gene transfer
- Mutualism between algae and chemoheterotroph protists
—> Rise of chloroplasts in algae from primary endosymbiosis —>Secondary endosymbiosis between algae that already had chloroplast & protists —> Photosynthetic protists
3 ecological roles of protists
- Primary producers = phytoplankton: desmids, diatoms, volvox —> Algae and cynobacteria
- Primary consumers = zooplankton & Decomposers: ciliates, amoeba —> Protozoa and smaller animals
- Symbionts: parasites of plants and animals & mutualists
What are algal blooms?
Rapid increase in abundance of algae in fresh water and marine ecosystem
- Produced by eutrophication: excessive algal growth due to increased in resources and nutrients
- Can be natural (increase of nutrients from bottom of ocean) or human-induced (phosphate in laundry detergent)
- Harmful algal blooms = red tides —> when toxin-producing dinoflagellates reach high densities and poison shellfish which can poison organisms that use these shellfish for food
