Protists Chapter 29

2 Protists Protists are the most diverse of the four eukaryotic kingdoms -Unicellular, colonial and multicellular groups The kingdom Protista is paraphyletic Some protists are surrounded by Extracellular Material deposited outside of the plasma membrane

3 Protists -The 15 major protist phyla are grouped into seven major monophyletic groups -However, 60 lineages cannot be placed with confidence

4 Protists

5 Eukaryotic Origins Eukaryotic cells differ from prokaryotes by the presence of a cytoskeleton and organelles Appearance of eukaryotes in microfossils occurred about 1.5 BYA

6 Eukaryotic Origins The nucleus and endoplasmic reticulum arose from infoldings of prokaryotic cell membrane

7 Many organelles evolved via endosymbiosis between an ancestral eukaryote and a bacterial cell Over time, most organellar genes moved into the nucleus -Therefore, these organelles cannot be grown in pure culture

8 Secondary endosymbiosis -Red and green algae engulfed cyanobacteria -Brown algae engulfed red algae

9 General Biology of the Protists Nutrition -Phototrophs -Heterotrophs -Phagotrophs – Particulate food matter -Osmotrophs – Soluble food matter -Mixotrophs are both phototrophic and heterotrophic

10 General Biology of the Protists Asexual reproduction -Typical mode of reproduction -Some species have an unusual mitosis -Binary fission = Equal cells -Budding = Progeny cell smaller -Schizogony = Multiple fission Sexual reproduction -Union of haploid gametes which are produced by meiosis

11 Diplomonads and Parabasalids -Are closely related to the early, now extinct eukaryotic cell -Flagellated -Lack mitochondria Diplomonads -Have two nuclei -Giardia intestinalis Parabasalids -Have undulating membranes -Trichomonas vaginalis

12 Euglenozoa Euglenoids were among the earliest eukaryotes to possess mitochondria -1/3 rd have chloroplasts -All have a flexible pellicle -Stigma – Movement towards light

13 Euglenozoa Kinetoplastids -Unique, single mitochondrion with 2 types of DNA maxicircles and minicircles (expressed genes are used in RNA editing and glycolysis) -Trypanosomes cause human diseases -African sleeping sickness – Tsetse fly -Escapes immune systems because only one of variable antigen genes is expressed at a time on the glycoprotein coat

14 Alveolata Alveolata have flattened vesicles called alveoli -These function like Golgi bodies below the cell membrane

15 Alveolata Dinoflagellates -Unicellular with two unequal flagella -Live in aquatic environments -Most are photosynthetic -Reproduction is primarily asexual -About 20 species produce powerful toxins that harm vertebrates...“Blooms” are responsible for red tide--kills marine vertebrates

16 Alveolata Apicomplexans (Spore-forming animal parasites) Plasmodium -An apicomplexan that causes malaria -Organism has a very complex life cycle

17 Alveolata Ciliates Paramecium -Have two types of nuclei -Macronucleus = Divides by mitosis -Responsible for physiological functions -Micronucleus = Divides by meiosis -Involved in conjugation -Fusion of two cells of different mating types

18 Paramecium

19 -Food vacuoles = Digestion of food -Contractile vacuoles = Regulation of water balance

20 Stramenopila Stramenopiles have very fine hairs on their flagella -A few species have lost their hairs during evolution

21 Stramenopila Brown algae -Kelps -Grow in relatively shallow waters throughout the world -Life cycle involves alternation of generations -Sporophyte = Multicellular and diploid -Gametophyte = Multicellular and haploid

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23 Stramenopila Diatoms (Phylum Chrysophyta) -Unicellular organisms -Have unique double shells made of opaline silica -Some move using raphes--lined with vibrating fibrils

24 Rhodophyta Rhodophyta, or red algae, range from microscopic to very large sizes -Have accessory photosynthetic pigments within phycobilisomes

25 Choanoflagellida Choanoflagellates are most like the common ancestor of all animals -Single emergent flagellum, surrounded by funnel-shaped contractile collar -Use collar to feed on bacteria

26 Protists Without a Clade Amoebas are paraphyletic -Rhizopoda (True amoebas) -Move by means of cytoplasmic projections called pseudopods -Actinopoda (Radiolarians) -Glassy exoskeletons made of silica -Needlelike pseudopods

27 Protists Without a Clade Foraminifera are heterotrophic marine protists -Have pore-studded shells called tests, through which thin podia emerge (for swimming and feeding) -Have complex life cycles with haploid and diploid generations -Limestones are rich in forams -White cliffs of Dover

28 Slime molds w/o a clade 1. Plasmodial slime molds -Stream along as a plasmodium, a nonwalled, multinucleate mass of cytoplasm -Ingests bacteria and other organic material -When food or moisture is scarce, organism forms sporangia, where spores are produced

29 2. Cellular slime molds -Individual organisms behave as separate amoebas -Move through soil ingesting bacteria -When food is scarce, organisms aggregate to form a moving slug -Slug differentiates into a sorocarp with spores that differentiate into amoebas again Slime molds w/o a clade