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Prokaryotes and Viruses. Characteristics of Prokaryotic Cells  Single-celled bacteria and archaeans  No nucleus or membrane-bound organelles  Smallest,

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Presentation on theme: "Prokaryotes and Viruses. Characteristics of Prokaryotic Cells  Single-celled bacteria and archaeans  No nucleus or membrane-bound organelles  Smallest,"— Presentation transcript:

1 Prokaryotes and Viruses

2 Characteristics of Prokaryotic Cells  Single-celled bacteria and archaeans  No nucleus or membrane-bound organelles  Smallest, most widely distributed, numerous, and metabolically diverse organisms Autotrophs and heterotrophs

3 Prokaryote Cell Shapes  Spheres (cocci), rods (bacilli), spirals (spirilla)

4 Prokaryote Cell Structures  Typical surface structures Cell wall Outermost protective capsule or slime layer One or more flagella Pili

5 A Prokaryotic Cell

6 Flagella and Pili

7 Prokaryotic Fission

8 Prokaryotic Cell Characteristics

9 The Bacteria  The most common and diverse prokaryotes Some are pathogens (cause disease in a host)

10 Food Poisoning

11 Bacterial Diversity: Cyanobacteria  Oxygen-releasing photoautotrophs Chloroplasts probably evolved from ancient cyanobacteria by endosymbiosis

12 Bacterial Diversity: Gram-Positive Bacteria  Have thick walls Endospores resist heat, boiling, irradiation, acids and disinfectants Some are human pathogens

13 Bacterial Diversity: Chlamydias  Chlamydias All are intracellular parasites of animals Obtain ATP from host cells Some sexually transmitted diseases (C. trachomatis)

14 Bacterial Diversity: Spirochetes  Spring-shaped Live on their own or in hosts Some are pathogens

15 Archaean Physiology  Halophiles (salt lovers), extreme thermophiles, and methanogens (methane makers)

16 Archaeans in Extreme Environments

17 The Viruses  Viruses are noncellular infectious particles that cannot reproduce on their own  Viruses infect a host cell; their genes and enzymes take over the host’s mechanisms of replication and protein synthesis

18 Viral Structures

19 Prion Infections Prions Proteins that occur naturally in the vertebrate nervous system, but can cause fatal disease when they misfold

20 Antibiotic Resistance  Use of antibiotics favors antibiotic-resistant bacteria  Genes that convey drug resistance can arise by mutation, may spread among members of the same or different species by conjugation

21 Protists – The Simplest Eukaryotes

22 An Evolutionary Road Map  Protists The simplest eukaryotes Most are single-celled Some are multicelled and large

23 Protist Structure  Protist cells have a nucleus (eukaryotes)  Most have one or more mitochondria  Many have chloroplasts that evolved from cyanobacteria or from another protist  Dominant stage of life cycle: Haploid or diploid

24 Protist Evolutionary Tree

25 Comparing Prokaryotes and Eukaryotes

26 Key Concepts: SORTING OUT THE PROTISTS  Protists include many lineages of single-celled eukaryotic organisms and their closest multicelled relatives  Gene sequencing and other methods are clarifying how protist lineages are related to one another and to plants, fungi, and animals

27 Ancient Flagellates  Flagellated protozoans Single-celled heterotrophs with flagella Unwalled cells, pellicle retains shape  Most euglenoids live in freshwater Some have chloroplasts that arose by secondary endosymbiosis from a green alga Contractile vacuoles expel excess water

28 Disease-Causing Flagellates  Trichomonas vaginalis  Trypanosoma brucei

29 Shelled Amoebas  Foraminiferans and radiolarians Single-celled heterotrophs with a secreted shell Many openings for pseudopods

30 Alveolates  All alveolates have tiny sacs (alveoli) beneath the plasma membrane All single-celled  Examples: Ciliates, dinoflagellates, and apicomplexans

31 Ciliates  Aquatic predators and parasites with many cilia Example: Paramecium

32 Dinoflagellates  Aquatic heterotrophs and autotrophs with a cellulose covering Photosynthetic protists cause algal blooms in nutrient-rich water

33 Apicomplexans  Heterotrophs: Parasites living in animal cells Cell-piercing structure made of microtubules Reproduce sexually and asexually in host cells Only gametes have flagella Example: Plasmodium (malaria)

34 Malaria  Plasmodium species cause malaria

35 Single-Celled Stramenopiles  Two flagella, one with hairlike filaments  Oomycotes Heterotrophs (decomposers and parasites) that grow as a mesh of absorptive filaments Some parasitic species are important plant pathogens

36 Photosynthetic Stramenopiles  Diatoms, coccolithophores, and golden algae Often part of the phytoplankton Photosynthetic cells (contain fucoxanthin)  Hard parts accumulate as mineral deposits Coccolithophores (calcium carbonate plates): Chalk and limestone Diatoms (silica shells): Diatomaceous earth

37 Stramenopiles of the Phytoplankton

38 Brown Algae  Multicelled, photosynthetic stramenopiles Include microscopic strands and giant kelps (the largest protists; ecological and commercial value)

39 Green Algae  Chlorophytes (most green algae) and charophytes (closest relatives of plants) Have chloroplasts with chlorophylls a and b Store carbohydrates as starch grains

40 Red Algae  Most red algae are multicelled Cultivated for commercial products

41 Amoebozoans  Amoebas (single cells) and slime molds (“social amoebas”) Heterotrophic, free-living

42 Slime Molds  Plasmodial slime molds Feed as a multinucleated mass


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