Exploring Diversity

Protists

Characteristics

• Most diverse of all organisms• Most are unicellular, microscopic organisms

• Most reproduce by asexual reproduction, some can reproduce sexually

• Carry out cell division• Protists are thought to have evolved 1.5 billion years ago

What Unites Protists?

• Kingdom contains all eukaryotes that cannot be classified as animals, plants, or fungi

• Lack specialized features that characterize the other 3 multicellular kingdoms

• Major phyla are very different from one another

Protist Video

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Amoebas• Phylum: Rhizopoda• Protists that move by using flexible, cytoplasmic extensions pseudopodia

• Reproduce asexually• Live in fresh/salt H2O

Algae

• Protists that autotrophs (uni/multicellular)

• Distinguished by the type of photosynthetic pigment they contain, & their cell or body shape

• 3 Types:– Green Algae (mostly freshwater & unicellular)

– Red Algae (most are marine & multicellular)– Brown Algae (most marine & multicellular)

Green Algae

• Most are freshwater unicellular organisms

• Contain the same pigments found in the chloroplasts of plants

Red Algae• Found in warm ocean waters• Red pigments are efficient at absorbing light that penetrates deep waters

Brown Algae• Found mostly in marine environments

• Larger brown algae Kelp, grows along coasts – provide food & shelter for different organisms

• Among the largest organisms on Earth

Diatoms• Phylum: Bacillariophyta• Photosynthetic, unicellular protists with double shells

• Found in oceans & lakes• Important producers in food chain

Dinoflagellates• Unicellular phototrophs, most are marine

• Some produce powerful toxins• Create poisonous “red tides” that occur in coastal areas

• Reproduce asexually

Euglenoids• Freshwater protists with 2 flagella, generally (example Euglena)

• 1/3 contain chloroplasts & are photosynthetic. 2/3 are heterotrophic

• Asexual reproduction

Kinetoplasts

• Unicellular heterotrophs, with at least 1 flagellum, some have thousands

• One type causes African sleeping sickness

• Trichonympha live in gut of termites and help to digest wood

Ciliates• Example Paramecium• Have large numbers of cilia (hairlike projections)

• Complex unicellular heterotrophs• Reproduction is usually asexual, can reproduce sexually by conjugation

Parmecium Movie

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Protistan Molds

• Heterotrophs with some mobility

• Originally thought to be related to fungi

Cellular Slime Molds

• Resemble amoebas • During environmental stress, they gather together & move toward a fixed center

Plasmodial Slime Molds

• Group of organisms that stream along as a plasmodium mass of cytoplasm that looks like an oozing slime

• As the move, they engulf bacteria & other organic material

Sporozoans

• Parasitic protists that form spores during their reproductive cycle

• All are parasitic & cause many serious diseases

• Ex.) Cryptosporidium found in feces of infected animals

Beneficial Protists• Many live in digestive tracts of humans & the digestive tracts of animals that humans eat (help cows digest cellulose)

• Make up plankton in ocean (producers in food web)

• Major oxygen producers• Break down dead materials (recycle)

Malaria

• One of the most deadly diseases in humans

• Symptoms: severe chills, fever, sweating, confusion, & great thirst

• Spread by the bite of certain mosquitoes

• Treatment: quinine chemical from the bark of the cinchona tree