Protists Chapter 28

What you need to know! Protista is no longer considered an independent kingdom. They are part of the Eukaryotes doman and are very diverse. How Chloroplasts and mitochondria evolved through endosymbiosis

*Domain Eukarya Kingdom Protista (includes): Phylum: Protozoa (euglena, amoeba, paramecium, malaria) Phylum: Crysophyta (diatoms, golden algae) Phylum: Pyrrophyta: (dinoflagellates)

*Metabolism Protists are the most nutritionally diverse of all eukaryotes: Most protists are aerobic, with mitochondria for cellular respiration. Some protists are photoautotrophs with chloroplasts. Still others are heterotrophs that absorb organic molecules or ingest larger food particles. A few are mixotrophs, combining photosynthesis and heterotrophic nutrition

Characteristics Protists are eukaryotes Can be unicellular, colonial, or multicellular Predecessor to other eukaryotes: plants, fungi, and animals. Fossils date back 2.1 billion years Some of the most complex cell structures found –Special organelles: contractile organelle (primitive excretion, H 2 0 balance), eye spots (primitive sight), anal pores (primitive waste excretion)

Specifics Types: 1.Absorptive, protists (fungus-like) 2.Protozoa - ingestive, animal-like protists 3.Algae - photosynthetic, plant-like protists. Important Structures: Flagella: Protists have a flagella or cilia during some time in their life cycles. –The eukaryotic flagella are extensions of the cytoplasm with a support of a microtubule system (made from tubullin) –Cilia are shorter and more numerous than flagella.

Reproduction protists can reproduce asexually or sexually Many protists form resistant colonies (cysts) that can survive harsh conditions. Protists are the first group to show “alternation of generation”: 1.Most protists are haploid organisms (n), called gametophytes 2.Gametophytes produce gametes 3.Gametes fuse to form a zygote 4.The Zygote develops into a sporophyte (not the main organisms) 5.The Sporophyte produces haploid spores that germinate into gametophytes

Habitat Protists are found almost anywhere there is water: Oceans, ponds, and lakes, but also damp soil, leaf litter, and other moist terrestrial habitats. Protists are also important parts of the plankton, communities of organisms that drift passively or swim weakly in the water. Phytoplankton (including planktonic eukaryotic algae and prokaryotic cyanobacteria) are the bases of most marine and freshwater food chains.

*Lifestyle Many protists are symbiots that inhabit the body fluids, tissues, or cells of hosts. These symbiotic relationships span the continuum from mutualism to parasitism (malaria, giardia)

*Evolution Endomembrane system of eukaryotes (nuclear envelope, endoplasmic reticulum, Golgi apparatus, and related structures) may have evolved from in-folding of plasma membrane. Mitochondria and chloroplasts were incorporated through endosymbiosis

Euglena Freshwater microscopic algae, single celled autotrophic organism (phytoplankton) Contractile vacuole: bladder- like, pulsing structure that pumps out excess water that enters the cell due to the cell being hyperosmotic in fresh water Eyespot: detection of light direction Flagellum: movement toward light source

Amoebas Pseudopods: extensions of the cytoplasm –Capturing prey, locomotion Heterotrophic Movement by pseudopods (false feet): bulging out of plasma membrane followed by cytoplasm

Paramecium Coordinated movement through ciliates Complex organelles: contractile vacuole for osmoregulation (pumping out water), oral groove (mouth), anal pore (duh)

Radiolarians Skeleton pseudopods to increase surface area

Foraminiferans Beautifully shaped calcium carbonate or silica shelled protists

Malaria (protozoan) transmitted by infected mosquito

Phylum Crysophyta/Diatoms Abundant in plankton and sediments Have silica shells Top and bottom shells fit together like boxes

*Well Known Members Infamous: Giardia Trypanosomes Malaria Cute Paramecium Amoeba Mistaken as other organisms Brown, green, and red algae Giant Kelp