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Protista (protist pl.) are taxonomically classified into the Kingdom Protista
All protists are eukaryotic (have a nucleus), lack tissues, and are in moist areas.
An eukaryotic organism that's no a plant, animal, or fungi is a protest. They're found anywhere on Earth.
Positive protists
Positive protists
Protists are crucial in aquatic ecosystems, some inhabiting moist terrestrial ecosystems.
Producers: Some are photosynthetic and are major producers in the world’s oceans.
Consumers: Non-photosynthetic protists are important consumers, especially at the microscopic level, where they dominate the lowest levels of most aquatic food pyramids.
Examples of protist
Examples of protist
Nori: Seaweed used to wrap sushi rolls
Food additives: Agar and carrageenan (food thickeners), are made from seaweed, a protist!
Other products: Used in toothpaste, cosmetics and paints
Harmful protists
Harmful protists
Some protists cause serious disease.
Amoebic Dysentery
Entamoeba histolytica
Sleeping Sickness
African trypanosomiasis
Malaria
Plasmodium falciparum
Beaver feaver
Beaver feaver
Beaver fever is less serious but of concern in Ontario is giardiasis, or ‘beaver fever’.
It can cause Giardia lamblia, the most common intestinal parasite in humans in NA.
The symptoms are intense diarrhea, dehydration, nausea, stomach cramps and gas
Common in bodies of water - host infected by drinking contaminated water.
Origins
Origins
Protists were the first eukaryotes. Mitochondria and chloroplasts are thought to have originated by endosymbiosis
Proteobacteria ingested → mitochondria
Cyanobacteria ingested → chloroplasts
Endosymbiosis is a relationship in which a single-celled organism lives within another organism.
Present-day mitochondria and chloroplasts:
have two membranes
Their inner membranes are similar to those of their ancestral prokaryote, while their outer membranes match the cell membranes of the eukaryote.
have their own internal chromosomes, which are very similar to prokaryotic chromosomes
Reproduce independently within eukaryotic cells by binary fission (like prokaryotes)
Protists are the most diverse kingdom
The Kingdom Protista is not based on evolutionary kinship, but more on convenience as a “catch-all” for species that do not fit into the four other kingdoms
More meaningful classifications will likely soon replace this single kingdom
Types
Types
Scientists classified protista into 3 groups:
Animal-like protists (protozoan) (e.g. paramecium)
Plant-like protists (e.g. euglena)
Fungus-like protists (e.g. slime molds)
Representive protista
Representive protista
Euglenoids
Euglenoids
Autotrophs and photosynthetic
Unicellular
Usually 2 flagella for moving
Stiff proteins on outer surface covering
Plant-like
Ciliates
Heterotroph
Unicellular
Very complex internal structure
Many cilia and no cell walls
Animal-like
Apicomplexa
Heterotrophs
Unicellular
No cell wall
All are parasites of animals
Animal-like
Plant-like diatoms
Amoebas
Slime molds
Some protista move with tiny hair called cilia, like paramecium.
Paramecium are heterotrophic, macro and micronuclei specialized vacuoles that contract to eliminate excess water a gullet (mouth) for taking in food cilia for movement trichocysts that release long fibers for defence
Other protista use a "false foot"/pseudo pod, like the euglena.
Euglena autotrophic use flagella. It contains chloroplast for photosynthesis eyespot for detecting light stiff flexible supporting layer called a pellicle large flagella for movement
Some protista are motionless, like diatoms floating along.
Reproduction
Reproduction
Specific reproduction mechanisms vary among many protist types. Some can mainly reproduce asexually, others may predominantly rely on sexual reproduction.
Many protists reproduce asexually through processes such as binary fission, budding, or fragmentation.
Binary fission: Protist, like amoeba, algae, and many others divides into two daughter cells, each genetically identical to the parent cell. This method is common among unicellular protists like bacteria and some algae.
Budding: A small outgrowth or bud forms on the parent cell, eventually detaching to become a new individual. This method is seen in organisms like yeast and some algae.
Fragmentation: The parent organism breaks into fragments, each that can grow a new one, which is common in some multicellular protists like some algae species.
Sexual Reproduction: Some protists also undergo sexual reproduction, involving the exchange and fusion of genetic material between two individuals.
Conjugation: This involves the temporary fusion of two individuals and the exchange of genetic material. It's common in certain groups of protists like ciliates (e.g., Paramecium).
Gamete Fusion: Protists may produce specialized reproductive cells (gametes) that fuse to form a zygote, which then develops into a new individual. This process is similar to sexual reproduction in plants and animals.
Ecosystem interaction
Ecosystem interaction
Protists play key roles as major producers in the world’s oceans. These photosynthetic protists, such as green, red and brown algae have large gas-filled bladders that help them float towards the light. → This allows for photosynthesis. Phytoplankton are microscopic algae that live in marine environments. → They produce about half Earth’s oxygen.
The world population of Protista is thought to be declining 1% per year, possibly due to
warming ocean temperatures
increasing acidity (affecting ability to build protective coating)
Malaria and climate changes
Malaria and climate changes
Malaria is a disease caused by plasmodiums (protista) by a parasite spreading to humans through infected mosquitoes bites.
Those who have malaria usually feel very sick with high fevers and shaking chills.
While the disease is rare in temperate climates, it's common in tropical and subtropical countries.
As climate changes increase, Malaria will spread to previous unaffected areas.
Plasmodium
Plasmodium
Plasmodium vivax, malariae, and falciparum are a few plasmodium species causing malarias to humans.
Plasmodium falciparum is the most violent and life-threatening.
Plasmodiums live as parasites female mosquitos and get into humans through their bites.
Plasmodium life cycle
Plasmodium life cycle
Sporozoite: An infected female mosquito first bites a human. To enjoy the blood, the insect secretes its saliva into the bloodstream, preventing blood coagulation (process of blood clot which heals the body), transferring the malarial parasite into the body in the form of sporozoites, a stage of plasmodium, where they can infect the host by targeting their liver, staying inside for a long time while reproducing asexually to multiply before nursing out of the liver cells.
Merozoite: Now as merozoites, after getting back into the bloodstream from the liver, the plasmodiums target RBCs.
Trophozoite: In RBCs, they form a ringed-strucutre called trophozoite. Trophozoite plasmodiums can have two fate:
Asexual Cycle: Most start with asexual cycles to create new merozoites exponentially, which is too large for RBCs, which burst and release the plasmodium to attack more RBCs swiftly.
Sexual Cycle: The trophozoites plasmodiums create 2 different gametocytes (germ cells of plasmodiums). Gametocytes let themself sucked by an uninfected mosquito sucking the host.
Zygote: In the mosquito, gametocyte of all genders fuse to zygotes in their guts.
Ocystes are developed and cross the gut wall to reach the salivary glands, where ocystes release several sporoiztes, mature plasmodiums, to be ready to infect more hosts.
Life cycles of multicellular
Life cycles of multicellular
Some make sex cells (sperm and eggs) that are haploid (half of genetic informations or “n” )
When these eggs and sperms fuse,
the resulting cell is called a zygote, most of which are diploid (contain two copies of every chromosome, or “2n” )
Brown Algae Life Cycle
Brown Algae Life Cycle
The large brown alga is a diploid (2n) sporophyte that produces and releases single-celled haploid (n) spores.
These spores then find and attach to a surface and begin dividing and growing into multicellular haploid gametophytes (male and female).
These gametophytes eventually produce haploid sperm and eggs. When an egg is fertilized by a sperm, it becomes a diploid (2n) zygote that grows into a multicellular sporophyte.
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