Protists Flashcards
1
Q
What are protists?
A
- A very diverse group
- Basically everything that is a eukaryote but not a land plant, fungi or animal
- Most are very small
2
Q
Who discovered protists?
A
Leeuwenhoek looking down early microscope:
» “No more pleasant sight has met my eye than this, of so many thousands of living creatures in one small drop of water”
3
Q
Are protists uni or multicellular?
A
Most unicellular, some form colonies, and simple multicellular forms
4
Q
How do Protists get their nutrition and reproduce?
A
- Most nutritionally diverse of all eukaryotes, include:
1. Photoautotrophs, which contain chloroplasts
2. Heterotrophs, which absorb organic molecules or ingest larger food particles
3. Mixotrophs, which combine photosynthesis and heterotrophic nutrition - Can reproduce asexually or sexually
5
Q
What are the four super groups of protist phylogeny?
A
» Excavata
» SAR
» Archaeplastida
» Unikonta
6
Q
What is clade excavata?
A
- Monophyletic group
- Some have an “excavated” feeding groove
- Can be predatory heterotrophs, photosynthetic autotrophs, mixotrophs, and parasites
- Example: Giardia intestinalis
» Flagellated unicellular eukaryote
» Parasitic in human intestine
7
Q
What is Giardia?
A
- A parasitic protist from the excavata clade:
- shed in faeces
- Commonly transmitted in contaminated water
- Giardia has protective outer shell → can survive outside the body for long periods + is resistant to chlorine disinfection
» ≈2% adults, 6-8% children in developed countries
» Nearly 33% people in developing countries have had giardiasis
8
Q
What are the symptoms of Giardia?
A
- Symptoms appear around 1-3 weeks after infection, last 1-2 weeks or longer
- Acute symptoms include
» Diarrhea
» Gas
» Greasy stools that tend to float
» Stomach or abdominal cramps
» Upset stomach or nausea/vomiting
» Dehydration (loss of fluids)
9
Q
What is the SAR Clade?
A
- Diverse monophyletic group of protists defined by DNA similarities
- divided into three main groups:
1) Stramenopiles
2) Alveolates
3) Rhizarians
10
Q
What are Stramenophiles?
A
- A main group of the SAR Clade
- Key organism in many environments
» Diatoms, brown algae and several pathogens - Diatoms are a key group of unicellular photosynthetic algae
» Highly diverse (≈100,000 species)
» Glass-like wall made of silicon dioxide (protection from predation)
» Yellow/brown due to brown plastids
» Usually reproduce asexually
» Store food in a form of oil, which make cells buoyant
11
Q
What are Diatoms?
A
- A branch of the Stramenophiles group in the SAR Clade
- Important component of plankton (free floating microorganism in marine and freshwater)
- Important source of fixed carbon
(20% of global carbon fixation) and 40% of marine primary productivity - Boom and bust population cycles
» Boom when conditions favourable (lots of nutrients, low predation)
» Then fall to the ocean floor, then when new nutrient upwelling, boom again
12
Q
What is brown algae
A
- A branch of the Stramenophiles group in the SAR Clade
- » All multicellular and mostly in marine
» Largest and most complex algae
» Have chlorophyll-a, chlorophyll-c & carotenoid pigments
» Store carbohydrate food reserves in the form of laminarin
» Cell walls consist of cellulose and lignin
13
Q
What are Alveolates?
A
- A main group of the SAR Clade
- Membrane-enclosed sac (“alveoli”) under the plasma membrane
14
Q
What are dinoflagellates?
A
- A branch of the Alveolates group in the SAR Clade
- Have flagella, and often encased in “armour plates”
- Important in phytoplankton (small marine photosynthetic organisms)
- Can have carotenoids as pigments giving rise to “red tides” when population blooms
» Some produce toxins, and can contaminate (and kill) invertebrates and fish (and humans who consume them)
15
Q
What are Apicomplexans?
A
- A branch of the Alveolates group in the SAR Clade
- Nearly all are parasites of animals
- Non-photosynthetic
» Although they have retained plastid - Example:
» Plasmodium and malaria
