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Protists
Section 18-1
Kingdom Protista
Eukaryotic – 200,000 species No simple set of common
characteristics Can be unicellular or multicellular Microscopic or very large Aerobic or anaerobic Autotrophic or heterotrophic Sexual or asexual reproduction
Evolution of Protists About 2 bya, prokaryotes began to
grow larger and develop internal membranes, like the nuclear membrane
Then evolved organelles to help with complex functions like the GA and ER
Endosymbiont hypothesis explains the evolution of the mitochondrion and the chloroplast
Sexual Reproduction Evolves First appeared about 300 million
years after the first protists Allowed for rapid evolution
because of the increased genetic variation
Eukaryotes experienced a huge adaptive radiation, leading eventually to the billions of eukaryotes we have today
Classifying Kingdom Protista Anything eukaryotic that cannot be
classified as a fungus, plant, or animal is put into Kingdom Protista
Further classified by the organisms they most resemble: Plant-like protists Animal-like protists Fungus-like protists
Plant-Like Protists
AKA algae Photosynthetic autotrophs that
contain chlorophyll About 30,000 different species Perform 30-40% of all
photosynthesis Can be unicellular or multicellular
Plant-Like Protists
Red Tide
Animal-Like Protists
AKA protozoans, first-animals Start out unicellular, but some
gather together to live in community at some point in their life cycle
Four phyla, classified by how they move
Flagellates Called
flagellates, because they move using flagella
Giardia
Sarcodines
Have pseudopods (false-feet) Amoeba
Amoeba
Ciliates Have cilia, tiny
hair-like structures for movement
Paramecium
Paramecium
Phylum Sporozoa
Called sporozoans
Parasitic, produce spores
Plasmodium falciparum
Fungus-Like Protists
Lack chlorophyll, absorb food through their cell walls
Called slime molds
Life Cycles of Protists
Varied life cycles Euglenophytes branched off before
sexual reproduction and therefore only reproduce asexually
Only genetic variation is from mutation
Reproduction in Algae
Alternates between sexual and asexual reproduction, as do green plants
Called alternation of generations
Diploid (2n) and haploid (n) cells switch back and forth
Reproduction in Algae Diploid generation called
sporophyte because it undergoes meiosis to produce haploid spores
Spores grow into haploid male and female cells called gametophytes
Gametophytes produce egg and sperm, which fuse to form zygote
Zygote develops into sporophyte
Alternation of Generations
Gametophyte
Sporophyte
Reproduction in Protozoans
Sarcodines (like Amoeba) reproduce asexually by binary fission
Sporozoans produce spores, which are reproductive cells formed without fertilization that can produce a new organism
Reproduction in Fungus-Like Protists Cellular slime molds spend most of
their lives as individual, free-moving amoeba-like cells
Under certain circumstances, they gather into a sluglike mass, which then forms a fruiting body
Fruiting body releases spores, which will develop into free-moving cells