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Characterizing and Classifying Eukaryotes Chapter 12. Eukaryotes. Major groups eukaryotes covered in a Micro course Protozoa Fungi Algae Helminths (we’ll save these till later) We’ll cover the medical importance of all of these groups in later lectures!.

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Characterizing and Classifying Eukaryotes Chapter 12

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Characterizing and classifying eukaryotes chapter 12

Characterizing and Classifying EukaryotesChapter 12



  • Major groups eukaryotes covered in a Micro course

    • Protozoa

    • Fungi

    • Algae

    • Helminths (we’ll save these till later)

      We’ll cover the medical importance of all of these groups in later lectures!

Classification of eukaryotic organisms

Classification of Eukaryotic Organisms

Figure 12.4



  • Diverse group defined by three characteristics

    • Eukaryotic

    • Unicellular

    • Lack a cell wall

  • With exception of apicomplexans (much more about these guys later!), they are motile by means of cilia, flagella, and/or pseudopodia

Distribution of protozoa

Distribution of Protozoa

  • Require moist environments

  • Most live worldwide in ponds, streams, lakes, and oceans; critical members of plankton

  • Others live in moist soil, beach sand, and decaying organic matter

  • Very few are pathogens

Nutrition of protozoa

Nutrition of Protozoa

  • Most are chemoheterotrophic

  • Obtain nutrients by phagocytizing bacteria, decaying organic matter, other protozoa, or the tissues of host

  • Few absorb nutrients from surrounding water

  • Dinoflagellates and euglenoids are sometimes considered protozoa but they are photoautotrophic and are traditionally grouped with the algae.



  • Chemoheterotrophic

  • Have cell walls typically composed of chitin

  • Lack chlorophyll; do not perform photosynthesis

  • Related to animals

  • Reproduction

    • All have some means of asexual reproduction

    • Most also reproduce sexually

Significance of fungi

Significance of Fungi

  • Decompose dead organisms and recycle their nutrients

  • Form beneficial associations with roots of vascular plants that help plant absorb water and minerals

  • Used for food and in manufacture of foods and beverages

  • Produce antibiotics

  • Important research tools

  • 30% cause diseases of plants, animals, and humans

  • Can spoil fruit, pickles, jams, and jellies

Fungal morphology

Fungal Morphology

Figure 12.16a

Fungal morphology1

Fungal Morphology

Figure 12.16b

Fungal morphology2

Fungal Morphology

Figure 12.16c

Nutrition of fungi

Nutrition of Fungi

  • Acquire nutrients by absorption

  • Most are saprobes

  • Some trap and kill microscopic soil-dwelling nematodes

  • Haustoria allow some to derive nutrients from living plants and animals

  • Most are aerobic; some are anaerobic; many yeasts are facultative anaerobes



  • Partnerships between fungi and photosynthetic microbes (green algae or cyanobacteria)

  • Grow on soil, rocks, leaves, tree bark, other lichens, and even on backs of tortoises; almost every habitat

  • Occur in three basic shapes – fruticose, crustose, foliose

  • Important in creation of soil from rocks

  • Eaten by many animals

Three basic shapes of lichens

Three Basic Shapes of Lichens

Figure 12.27



  • Diverse group of photoautotrophic aquatic organisms

  • Major role in aquatic food chains

  • Fix carbon dioxide into organ carbon

  • Produce somewhere between 50% and 80 % of the Earth’s oxygen

  • Morphology: Unicellular, colonial, or have simple multicellular bodies (thalli)

Algae d inoflagellates

Algae: Dinoflagellates

  • They have two flagella and may have armor (cellulose plates) or may be naked (without armor). Dinoflagellates have pigments and can carry on photosynthesis. Major component of phytoplankton.

  • Gonyaulax

    • Red tide

    • Paralytic shellfish poisoning

  • Noctiluca miliaris

    • Bioluminescent

Swimming with bioluminescent dinoflagellates

Swimming with bioluminescent dinoflagellates

Algae bacillariophyta diatoms

Algae: Bacillariophyta (Diatoms)

Diatoms are sometimes grouped with the golden algae (Chrysophyta)

Characterizing and classifying eukaryotes chapter 12


Golden algae

Phaeophyta brown algae

Phaeophyta (Brown algae)

  • Largest and most complex of the algae

  • Kelp is a brown algae

    • Giant kelp - up to 100 meters in size

  • Seaweeds = large, multicellular marine algae of coastal waters which include members of the Brown, Red, and Green algae groups

Australian bull kelp durvillea potatorum

Australian bull kelp (Durvillea potatorum)

Kelp forest

Kelp forest

Kelp forest1

Kelp forest

Red algae rhodophyta

Red algae (Rhodophyta)

Chlorophyta green algae

Chlorophyta (green algae)

  • Over 7000 species known

    • Freshwater and marine

    • Unicellular and multicellular forms

  • Volvox

  • Chlamydomonas

  • Spirogyra

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