Protists Domain Eukarya 2007-2008 Domain Bacteria Archaea Eukarya Common ancestor 2007-2008

Living Small Even a low-power microscope can reveal a great variety of organisms in a drop of pond water Protist is the informal name of the group of mostly unicellular eukaryotes Advances in eukaryotic systematics have caused the classification of protists to change significantly Protists constitute a polyphyletic group, and Protista is no longer valid as a kingdom

Which of these organisms are prokaryotes and which are Eukaryotes?

General characteristics Classification criteria eukaryotes not animal, plant or fungi The organisms in most eukaryotic lineages are protists, and Most protists are unicellular

Structural and Functional Diversity Protists exhibit more structural and functional diversity than any other group of eukaryotes Though most protists are unicellular, there are some colonial and multicellular species Single-celled protists can be very complex, as all biological functions are carried out by organelles in each individual cell

dinoflagellates & ciliates Great Diversity dinoflagellates & ciliates brown algae & diatoms euglenoids red algae green algae miscellaneous?

Be sure to know the 4 different Clades and 2 examples from each Be sure to know the 4 different Clades and 2 examples from each! Check out page 590-591  

Problems with Protist Classification Too Diverse! doesn’t reflect any evolutionary relationship amongst all kingdom members paraphyletic Euglenozoa Animals Streptophyta (includes land plants) Choanoflagellida Fungi Chlorophyta Rhodophyta Stramenopila Alveolata Archaea Bacteria Something’s not right here!

Protist Diversity The full spectrum of modes of life from unicellular to multicellular autotrophic to heterotrophic asexual to sexual reproduction pathogenic to beneficial sessile to mobile

Nutrionally Diverse Photoautotrophs, which contain chloroplasts Heterotrophs, which absorb organic molecules or ingest larger food particles Mixotrophs, which combine photosynthesis and heterotrophic nutrition

Protist Diversity Plant-like Protists autotrophs, photosynthesis Euglena algae diatoms

Protist Diversity Animal-like Protists heterotrophs, predators Amoeba Paramecium with food vacuoles stained red Protist Diversity Animal-like Protists heterotrophs, predators Amoeba Paramecium Stentor Amoeba ingesting a Paramecium

Protist Diversity Parasitic & pathogenic Protists malaria Giardia trypanosomes Plasmodium Giardia Trypanosoma

Protist Diversity Beneficial & necessary Protists phytoplankton small algae + diatoms much of the world’s photosynthesis produces ~90% of atmospheric oxygen zooplankton heterotrophic protists + animals key ecological role at base of marine food web

Mobility How Protists move flagellum cilia pseudopod

Evolution of Protist There is now considerable evidence that much protist diversity has its origins in endosymbiosis Endosymbiosis is a relationship between two species in which one organism lives inside the cell or cells of the other organism (the host)

Theory of Endosymbiosis mitochondrion internal membrane system aerobic bacterium Ancestral eukaryotic cell Eukaryotic cell with mitochondrion Paramecium & symbiont Chlorella photosynthetic bacterium chloroplast Eukaryotic cell with chloroplasts

Any Questions?? 2017-2018