Eukaryotic Evolution and Endosymbiosis

Kingdom Protista

• Protists are eukaryotic microbes which have a true nucleus.
• Protists show vast ecological diversity with 65,000 to 200,000 species.
• Examples of protists include amoebas, paramecium, and diatoms.
• Any organism that doesn't fit into other kingdoms is put into the protist kingdom.
• Some protists are large enough to be seen without a microscope.

Protists: Characteristics

• Protists are eukaryotic.
• Most protists are unicellular, however some can be simple multicellular.
• Some protists reproduce asexually through binary fission, multiple fission, or mitosis.
• Some protists reproduce sexually through meiosis.
• Most protists live in aquatic or damp environments, or within other organisms.
• Fungi, plants, and animals evolved from protists.

Protist Groups

• Protists are their own kingdom, divided into 3 groups
• The three groups are plant-like protists, animal-like protists, plus fungi-like protists

Unicellular Protists

• Animal-like protists are known as protozoans.
• Examples of animal-like protists are Amoebas, ciliates, and flagellates.
• Animal-like protists consume other organisms.
• Some animal-like protists are parasites.
• Plant-like protists make their own food through photosynthesis.
• Some plant-like protists consume organisms when light is unavailable.
• Examples of plant-like protists are Euglenoids, diatoms, and dinoflagellates.
• Some plant-like protists are symbionts.
• Fungus-like protists absorb nutrients from other organisms.
• Examples of fungus-like protists are slime molds and water molds.
• Some slime molds consume other organisms.
• Some water molds are parasitic.

Animal-like Protists

• Animal-like protists are often called PROTOZOA.
• Animal-like protists are heterotrophs
• Animal-like protists are unicellular.
• Animal-like protists often have contractile vacuoles that remove excess water.
• Animal-like protists live in aquatic environments as predators, decomposers, or in symbiotic relationships.
• Animal-like protists symbiotic relationships can be parasitism, mutualism and commensalism
• Animal-like protists are classified by how they move (motility).

Cercozoans: Phylum Cercoza

• Amoeba habitat includes moist soil, water and in other organisms
• Amoebas are herterotrophic
• Amoeba mobility is through pseudopods or "fake foot"
• Pseudopods are an extension of cytoplasm, and are used to ingest food.
• Amoeba cell organelles include cytoplasm, plasma membrane, and a nucleus.
• Amoeba typically lack cilia and flagella.

Brain-eating Amoeba

• Brain-eating Amoeba or Naegleria fowleri can be found in warm lakes/ponds, untreated swimming pools, hot springs, aquariums, and moist soil.
• Naegleria fowleri's food source is bacteria, but can feed on brain tissue when infecting humans.
• Naegleria fowleri infection occurs through the nose usually during water sports like diving or water skiing
• General symptoms of Naegleria fowleri infection are headache, fever, stiff neck, loss of appetite, vomiting, seizures, coma, and death.

Ciliates – Phylum Ciliophora

• Paramecium inhabit bodies of water, mostly stagnant and in other organisms
• Paramecium are heterotrophic
• Paramecium move using cilia for locomotion and particle manipulation
• Paramecium unique cell organelles include oral groove and gullet
• Cilia moves nutrients into the paramecium gullet.
• Paramecium have two nuclei, macro and micro

Paramecium Nuclei

• The macronucleus provides the nuclear RNA for vegetative growth.
• Mating cells exchange haploid micronuclei.
• A new macronucleus develops from a new diploid micronucleus
• Micronuclei are therefore involved in sexual reproduction

Flagellates: Phylum Zoomastigina

• Flagellates are found in aquatic environments, including snow, and within multicellular organisms as part of a mutualistic relationship or parasitic
• Flagellates are heterotrophic
• Flagellates move using one or more flagella
• Flagellates have elongated body and flagella

Sporozoans: Phylum Sporozoa

• Sporozoans are mostly parasitic.
• Sporozoans are heterotrophic.
• Reproduce through binary fission.
• Most Sporozoans alternate between sexual and asexual reproduction.
• Sporozoans mostly move without flagella, cilia, or pseudopods.
• Sporozoan's parasitic lifecycle includes often existing within 2 different host species.
• Sporozoans have a spore-like stage.
• Malaria is caused by Plasmodium.

Plasmodium Life Cycle

• Female Anopheles mosquitoes inject sporozoites into a host through a bite.
• Sporozoites move through the blood to the liver.
• Hepatocytes are infected by sporozoites.
• Sporozoites mature into schizonts that rupture and release merozoites
• Released merozoites infect erythrocytes
• Gametocytes mature in infected erythrocytes and are released into blood
• A mosquito ingests gametocytes from the blood of an infected host
• Gametocytes in mosquito are male (microgametocytes) and female (macrogametocytes)
• This then completes the life cycle in the mosquito.

Plant-like Protists

• Plant-like protists are commonly called algae.
• Chloroplasts allow algae to photosynthesize, most are autotrophic, but some are mixotrophic.
• Accessory pigments give a variety of colours red and green.
• Most algae reproduce asexually, some can reproduce sexually
• Algae live in wet/moist environments (ponds).

Diatoms

• Diatoms produce a lot of oxygen through photosynthesis
• 20-50% of the world's total oxygen is made by diatoms)
• Diatom cell walls are made of silica
• The shells of dead diatoms make up significant portion of the ocean floor - sometimes 800 m
• Diatoms are an important food source of aquatic organisms

Diatoms: Phylum Chrysophyta

• Diatoms are the most abundant type of phytoplankton living in aquatic environments
• Diatoms are unicellular
• Diatoms are auotrophic
• Diatoms reproduce through mitosis (asexual) or meiosis (sexual)
• Diatoms mobility is free floating
• Diatom cell walls are coated in silica in shoebox style

Diatom Reproduction

• Diatoms get their name from having a shape like a shoe box, with a fitting lid.
• Diatom reproduction is mostly asexual mitosis, but can reproduce via meiosis during unfavourable conditions

Dinoflagellates

• Dinoflagellates are phytoplankton living in aquatic environments
• Dinoflagellates are autotrophic
• Dinoflagellate mobility is through flagella which cause them to spin throught the water
• A dinoflagellate has two flagellum positioned 90° (perpendicular) to one another
• Dinoflagellate pigments give distinctive colours

Dinoflagellates and Coral

• Rapid dinoflagellate reproduction in time of optimal conditions and abundant nutrients causes algae blooms.
• This causes death or increased toxicity to marine life.
• Mutualism occurs while the dinoflagellates live within coral giving the coral it's colour
• When the reefs warm, the coral expels the dinoflagellates.
• This is called bleaching, and the coral dies.

Euglenoids

• Habitat is shallow water
• Euglenoids are autotrophic, but some can switch to heterotrophic when needed
• Mobilty through flagellum
• Flagellum and stigma (photoreceptor) allows flagellum to position the protist towards the light or away from light

Algae Groups

• Algae can be
  • Phylum Chlorophyta (green algae)
  • Phylum Phaeophyta (brown algae)
  • Phylum Rhodophyta (red algae)
  • Phylum Chrysophyta (golden algae)

Algae

• Most algae are aquatic but some are terrestrial.
• Can be found on moist soil, trees, and rocks.
• Algae can be unicellular or multicellular.
• Multicellular algae do not have tissues except for some brown algae
• Algae are autotrophic.
• Reproduce through mitosis (asexual) and meiosis (sexual)
• Float, or attach to objects in the water or on land
• Algae differ from the vascular plants by lacking true roots, stems, and leaves.

Fungus-like Protists

• Fungus-like protists Resemble fungi in appearance and lifestyle.
• Fungus-like protists however differ from true fungi at their cellular level, such as the cell wall.
• Reproduce with spores like fungus.
• Fungus-like protists are heterotrophs and feed on bacteria and rotting material.
• Examples of Fungus-like protists are water mould and slime mould.

Fungus-Like Protists:

• Two groups:
  • Plasmodial Slime Molds
  • Cellular Slime Molds

Plasmodial Slime Molds:

• Start out as individual amoeboid cells, but join to form a multi-nucleate mass with only one cellular membrane.
• Result is a "super-cell" containing multiple nuclei called a plasmodium
• Plasmodium then moves over dead, decaying material looking for bacteria (and fungi) to digest
• When plasmodium runs out of food/dries out it begins to make fruiting structures called sporangia
• Sporangia has diploid nuclei, and then undergoes meiosis to form haploid nuclei
• Haploid nuclei makes spores for aerial dispersal
• Dispersal by spores is fungi-like.
• When the spores land and germinate into haploid cells they can have two flagella or amoebae that fuse to form plasmodium.

Cellular Slime Molds:

• Rarely are cellular slime molds are visible to the naked eye
• Cellular slime molds have one nuclei is each.
• Individuals may join to form a pseudoplasmodium.