Kingdom Protista Characteristics –Algaelike or plantlike –Protozoa or Animallike –Funguslike –Unicellular –Multicellular –Eukaryotes

Kingdom Protista Algaelike or Plantlike All obtain energy by photosynthesis. All have chlorophyll a, but may have various other chlorophylls and different accessory pigments. Phyla –Euglenophyta One to three flagella, at their apical (leading) end –Dinoflagellates Two flagella- one is posterior, while the second is transverse and rest in an encircling mid groove perpendicular to the first flagellum. Some are bioluminescent. Others produce nerve toxins that concentrate in filter-feeding shellfish, which then cause illness in human when eaten.

Kingdom Protista Algaelike or Plantlike Phyla –Chrysophyta Golden algae Have one or two apical flagella –Diatoms Shells made of silica (SiO 2 ) –Chlorophyta Green algae Have both chlorophyll a and b Cellulose cell walls Store their carbohydrates as starch Believed to be the ancestors of plants Variation in sexuality.

Kingdom Protista Algaelike or Plantlike Phyla –Phaeophyta Brown algae Multicellular Have flagellated sperm cells. Some are giant seaweeds or kelps

Kingdom Protista Protozoa or Animallike Heterotrophs –Consume either living cells (being predatory or parasitic) or dead organic matter. Phyla –Rhizopoda Amoebas Move by extensions of their of their cell body called pseudopodia. Pseudopodia encircle food and absorb it by phagocytosis

Kingdom Protista Protozoa or Animallike Phyla –Zooflagellates Flagellated protozoa Some mutualistic species digest cellulose in the guts of termites. Others are parasites, such as Trypanosoma, which is transmitted by the tsetse fly and cause African sleeping sickness in humans.

Kingdom Protista Protozoa or Animallike Phyla –Sporozoa Parasites of animals No physical means of motility They form spores which are dispersed by one or more hosts that participate in the completion of their life cycle Sporozoan that causes malaria, spends part of its life cycle in mosquitoes and part in humans.

Kingdom Protista Protozoa or Animallike Phyla –Ciliophora Distinguished by their cilia, which they use for moving. Specialized structures –Mouth –Anal pore –Contractile vacuoles for water balance –Two kinds of nuclei (macronucleus and several small micronuclei) Paramecium

Kingdom Protista Funguslike Resemble fungi because they form either filaments or spore-bearing bodies similar to fungi. Three divisions:

Kingdom Protista Funguslike Acrasiomycota (cellular slime molds) –Exhibit both funguslike and protozoalike characteristics during their life cycle. –Spores germinate into amoebas which feed on bacteria. –When food sources are depleted, the amoebas aggregate into a single unit, which migrates as a slug. –The individual cells of the slug then mobilize to form a stalk with a capsule at the top similar to the spore- bearing bodies of many fungi. –Spores are then released, which repeat the cycle when they germinate.

Kingdom Protista Funguslike Myxomycota (plasmodial slime molds) –Grow as a single, spreading mass (plasmodium) feeding on decaying vegetation. –When food becomes unavailable or when the environment desiccates, stalks bearing spore capsules form. –Haploid spores released from the capsule germinate into haploid amoeboid or flagellated cells which fuse to form a diploid cell. –The diploid cell grows into the spreading plasmodium.

Kingdom Protista Funguslike Oomycota (water molds, downy mildew, and white rust) –They are either parasites or saprobes. –They are much like fungi in that they form filaments (hyphae) which secret enzymes that digest the surrounding substances. –The breakdown products of digestion are then absorbed.

Kingdom Protista Evolution of Eukaryotes Cellular structures and processes unique to eukaryotes: –Membrane-enclosed nucleus –Mitochondria –Chloroplasts –Endomembrane system –Cytoskeleton –Multiple chromosomes consisting of linear DNA molecules compactly arranged with proteins. –Life cycles that include mitosis, meiosis, and sex.

Kingdom Protista Evolution of Eukaryotes First process in eukaryotic evolution: –Specialized infoldings of the prokaryotic plasma membrane, may have produced: Nuclear envelope Endoplasmic reticulum Golgi apparatus

Kingdom Protista Evolution of Eukaryotes Second process in eukaryotic evolution: –Endosymbiosis hypothesis, Lynn Margulis, University of Massachusetts Probably led to the mitochondria and chloroplast Proposes that mitochondria and chloroplast were formerly small prokaryotes living within larger cells. Proposed ancestors of mitochondria were aerobic heterotrophic prokaryotes that became endosymbionts. Proposed ancestors of chloroplasts in early eukaryotes were photosynthetic prokaryotes, probably cyanobacteria, that became endosymbionts.

Kingdom Protista Evolution of Eukaryotes Evidence (mitochondria/chloroplast to bacteria) –Endosymbiotic relationships in the modern world. –Appropriate size –Inner membranes have several enzymes and transport systems that resemble those found on the plasma membrane of modern prokaryotes. –Replicate by a splitting process similar to binary fission in bacteria. –Contain a genome consisting of circular DNA not associated with histones or other proteins.

Kingdom Protista Evolution of Eukaryotes Evidence (mitochondria/chloroplast to bacteria) –Contain transfer RNA, ribosomes, and other items needed to transcribe and translate their DNA into proteins. –Ribosomes are more similar to prokaryotic ribosomes. Size Biochemical characteristics Sensitivity to certain antibiotics –Lang and Burger, University of Montreal Found that mitochondrial genome of the protist Reclinomonas americana closely matches that of bacteria in structure and function.