Lecture 20 Flashcards
What are coccolithophorids (Haptophyta)?
•Diverse protistan pirates that took up a red algal chloroplast and have Chl A and C. •A few species dominate open oceans and account for 10-15% of world’s carbon fixation and 20% of the oxygen we breath. •Cells are mixotrophic with a complex mechanism of prey capture. -accessory pigments= make them look golden brown -taking out carbon out of the atmosphere= the exoskeletons don’t get recycled for 100 000s of years -world’s greatest producers
What are the most important animal-like consumers in the Protista kingdom?
cilliates
What are features of cilliates?
• Unicellular • Diverse and complex • Covered with flagella called cilia (i.e., ciliates) • Two types of nuclei: Micronucleus and Macronucleus • Predatory - feed on bacteria, protists, other ciliates etc. • Example: Paramecium -cilia= same organisation as flagella -extremely complex for a unicellular organisms
Describe the structre of a cilliate:
What are the two nuclei in cilliates and their function?
-two nuclei, as they are so large and complex micronucleus= the typical, normal mitosis, macronucleus= where lot of the DNA transcribed= the housekeeping genes as the micro one couldn’t keep up- no precision needed in macronucleus as theere are 1000s of copies of each DNA bit so just pinched and separated into two
What are the cillia for in cilliates?
cilia= to move and accumulate food
-to set up current and bring in the food
What are choanoflagellates?
- (‘collar’ flagellates or sponge-like protists)
- • Aquatic habitats • Tiny, unicellular protists closely related to the choanocytes of sponges
- At the base of the phylogenetic tree that gave rise to the animals
- Heterotrophic consumers
- carnivororus and as long as smaller than them they’ll eat it= so they often eat even their own
- choanoflagellates= gave rise to animals
What are slime moulds (ameboid protists)?
-Slime Moulds - Amoeboid Protists
- Heterotrophs - absorb or engulf food after external digestion (like fungi)
- Major decomposers and recyclers
- Reproduce by spores in fruiting bodies called sorocarps
- Cellular slime moulds (Dictyostelids) - feed on bacteria
- Acellular slime moulds (Myxomycetes) - decomposers
- they break down food outside by enzymes and then ingest the nutristion= break down matter
- dicytoselids= feed externally as well
fruiting bodies= colourful
What is the reprodzctive cycle of slime moulds (ameboid protists)?
- no sex and no meiosis
- amoebae= eat bacteria when food runs out= chemical pheromone present=need to reproduce= they come together = pseudoplasmodium and then what looks like slugs=(more slugs may join together if happen to meet)and then sets down and spores in a different place with more food= all individuals but cooperate to make these structures= how does it happen? the mechanism not clear
What are the oomycetes?
- Superficially like true fungi, but related to diatoms and brown algae.
- Zoospore infects plant tissue; hyphal filaments penetrate and parasitize cells.
- Phytophthora infestans: late blight of potato.
- Phytophthora cinnamomi: eucalypt dieback
-look like fungi, even in microscope look similar
phytopthora= irish famine
- Fungal-like Absorbers and Recyclers
- they used to have a chloroplasts but now live like parasites
How do you recognise oomycetes from fungi?
filament walls of cellulose, nuclei are diploid 2N
-oogonia and zoospores=
because of zoospore(gamete)= know they are not fungi
-the flagella on those are the same as in the kelps etc= different from fungi
-but look like fungi otherwise
How did some protists undergo change from producers to absorbers?
- In protists that have lost the ability to photosynthesize, their chloroplasts have become reduced in size and limited in function.
- Some of these organisms have been shown to be protistan pirates
- Cells with reduced chloroplasts are often parasites, and many cause deadly diseases (e.g., malaria). We’re interested in the Apicomplexa.
-oomycetes= used to be red brown algae but for some reason lost chloroplast= life-style change
malaria= used to be protistan pirates red algae= used to photosynthesize
What are the apicomplexa?
-Endoparasites of animals (5000 species) such as Malaria and Toxoplasma
- Named for their apical complex - used to penetrate host cells(apical complex- attach and penetrate into other cell= apicomplexa (name comes from there)
- Why do botanists study Malaria? Reduced plastid called an apicoplast.
plasmodium= malaria also in apicomplexa
Why is malaria connected to apicomplexa?
- plasmodium=Parasite eats contents of red cell and grows and divides into 24 daughters
- Plant- like genes found in parasites – within a previously unidentified compartment (apicoplast) in malaria parasite
- Malaria chloroplast (apicoplast) has 4 bounding membranes
Results from secondary enodsymbiosis (4 membranes= used to be protistan pirate)
-the arrow= 2 sets of extra non nuclear genes, it has genes for chloroplasts
Why is herbicide possible treatement for malaria?
Can use herbicide: a compound that blocks chloroplast metabolism and in this case kills the parasite. due to the presence of the apicoplast taht has genes for a chloroplast
- as the plastid plant dna= idea for killing malaria as it has the plastid
- herbicides are very cheap to make (50 dollars a tonne)
- some are safe and we know how they work
- anti malarics= based on herbicides
