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