Lec 11: The protists Flashcards
Primary production
Production of organic compounds from carbon dioxide (photosynthesis)
Most life on earth reliant on organisms that carry out primary production
Fixed carbon: source of carbon & energy
Oceans’ main primary producers: photosynthetic protists & photosynthetic bacteria
Terrestrial: plants
Photosynthetic protists
Also referred to as microalgae
Phytoplankton
Carbon fixing protist
Produce ~50% of primary production
Across whole ocean surface (0-200m) where light can be useful for generation of photosynthesis
Macroalgae and marine plants
Important autotrophs
Intertidal, subtidal & neritic
Haptophytes
Produce blooms
Can be visible from space
Dinoflagellates
Produce toxic ‘algal blooms’
Diatoms
Produce ~40% of all primary production in oceans
Food chain
The sequence of predators and prey in biological community
Tropic level
The organism’s position in a food chain
Zooplankton
Key link between primary producers (phytoplankton/microalgae) and secondary consumers (fishes)
Has own food chain: starts with heterotrophic protists (unicellular) -> multicellular animals (larval forms of fish, invertebrates like corals etc)
Mutualistic symbiosis
Mutually beneficial relationships
Corals and zooxanthellae
Reef building corals harbour photosynthetic endosymbiotic protists (zooxanthellae)
Coral receives photosynthetically-fixed carbon
Zooxanthellae receive nitrogenous compounds, phosphates, CO2, and protection from UV light from their hosts
Life cycle of slime mould
Amoeba stage
Multinucleate stage or multicellular stage
Spore stage
Multinucleate stage
Spores release -> germinate -> sexual cycles -> fuse together -> zygote -> increases in size -> generate new nuclei in same body -> plasmodium
Sporangium forms -> produce spores -> germinate -> amoeboid cells
Multicellular stage
Spores form -> collect together -> slug -> release spores
Spores from sporocarp germinate-> form amoebae -> aggregate when food is scarce
The resulting multicellular slug migrates -> new sporocarp is formed
Increasing temp (climate change) in vector borne diseases
Increasing temp ->
Increasing replication rate of vector
Increasing replication rate of pathogen
Increase range of rector & pathogen
Bring diseases into naive populations
Trypanosomiasis
African sleeping sickness (symptom of CNS invasion)
Transmitted by tsetse fly bite to bloodstream
Necrosis of lymph system, heart, brain, CNS
Personality changes, daytime sleepiness with night time sleep disturbance and progressive confusion
Untreated survival rarely >4 years
Leishmaniasis
Transmitted to humans from rodents & canines by sand flies
Cutaneous form: most common
Visceral: severe. Parasites migrate to vital organs
Reproduces in macrophages
Cause skin & tissue degradation
Giardiasis
Transmitted by water borne cysts excreted by infected animals
Giardia attaches to & reproduces in intestines
Gastrointestinal disease -> severe & chronic diarrhoea, abdominal cramps, bloating, fatigue & weight loss
Amoebiasis
Causes amoebic dysentery (amoebiasis)
Water borne & faecal-oral routes of transmission (via cysts)
Produce suite of digestive enzymes -> degrade gut epithelial cells
Entamoeba histolytics can penetrate into bloodstream-> migrate to liver, lungs or skin
