Protists 9/11/2017. Endosymbiosis

Size: px

Start display at page:

Download "Protists 9/11/2017. Endosymbiosis"

Delilah Jacobs
6 years ago
Views:

Protists Chapter 28 Most eukaryotes are single-celled organisms Protists are eukaryotes Eukaryotic cells have organelles and are more complex than

Protists exhibit more structural and functional diversity than any other group of eukaryotes Single-celled protists can be very complex, as all biological

chloroplasts Heterotrophs absorb organic molecules or ingest larger food particles Mixotrophs Endosymbiosis Endosymbiosis is the process in which a

1 Protists Chapter 28 Most eukaryotes are single-celled organisms Protists are eukaryotes Eukaryotic cells have organelles and are more complex than prokaryotic cells Most protists are unicellular, but there are some colonial and multicellular species Structural and functional diversity in Protists Protists exhibit more structural and functional diversity than any other group of eukaryotes Single-celled protists can be very complex, as all biological functions are carried out by organelles in each individual cell Protists, the most nutritionally diverse of all eukaryotes, include: Photoautotrophs contain chloroplasts Heterotrophs absorb organic molecules or ingest larger food particles Mixotrophs Endosymbiosis Endosymbiosis is the process in which a unicellular organism engulfs another cell Mitochondria Aerobic prokaryote Plastids Photosynthetic cyanobacterium The plastid-bearing lineage of protists evolved into red and green algae 1

2 Four Supergroups of Eukaryotes Excavata SAR (Stramenopiles, Aveolates, Rhizarians) Archaeplastida Unikonta Polyphyletic Group Excavates modified mitochondria unique flagella Diplomonads Lack plastids and most live in anaerobic environments Parabasalids Trichomonas vaginalis, a sexually transmitted disease 2

0.2 m 9/11/2017 Euglenozoans Includes predatory

Chromalveolates may have originated by secondary

Alveolates Members of the clade Alveolata have

membrane The alveolates include Flagellum Alveoli

Two flagella and each cell is reinforced by cellulose

3 0.2 m 9/11/2017 Euglenozoans Includes predatory heterotrophs, photosynthetic autotrophs, and parasites Chromalveolates may have originated by secondary endosymbiosis The proposed endosymbiont is a red alga Alveolates Members of the clade Alveolata have membranebounded sacs (alveoli) just under the plasma membrane The alveolates include Flagellum Alveoli Dinoflagellates Apicomplexans Ciliates Dinoflagellates Two flagella and each cell is reinforced by cellulose plates Diverse group of aquatic phototrophs, mixotrophs, and heterotrophs Cause toxic red tides 3

Apicomplexans Parasites of animals Most have sexual and asexual stages that require two

humans to complete its life cycle Ciliates Use of cilia to move and feed Large

two individuals exchange haploid micronuclei Paramecium Stramenopiles Important

flagellum Diatoms Unicellular algae with a unique two-part, glass-like wall of hydrated

compose much of the sediments known as diatomaceous earth This removes carbon dioxide

for their color, which results from their yellow and brown carotenoids The cells of

4 Apicomplexans Parasites of animals Most have sexual and asexual stages that require two or more different host species for completion Plasmodium requires both mosquitoes and humans to complete its life cycle Ciliates Use of cilia to move and feed Large macronuclei and small micronuclei Genetic variation results from conjugation, in which two individuals exchange haploid micronuclei Paramecium Stramenopiles Important phototrophs as well as several clades of heterotrophs Most have a hairy and smooth flagellum Diatoms Unicellular algae with a unique two-part, glass-like wall of hydrated silica Major component of phytoplankton and are highly diverse Fossilized diatom walls compose much of the sediments known as diatomaceous earth This removes carbon dioxide from the atmosphere and pumps it to the ocean floor Golden algae Golden algae are named for their color, which results from their yellow and brown carotenoids The cells of golden algae are typically biflagellated, with both flagella near one end Most are unicellular, but some are colonial 4

Brown algae Alternation of generations Largest and most complex algae All are multicellular, and

have evolved among the multicellular algae The most complex life cycles include an alternation of

are structurally different, while isomorphic generations look similar Oomycetes Water molds, white

filaments (hyphae) that facilitate nutrient uptake Their ecological impact can be great, as in

by DNA similarities Cercozoans Include most amoeboid and flagellated protists with threadlike

5 Brown algae Alternation of generations Largest and most complex algae All are multicellular, and most are marine Brown algae include many species commonly called seaweeds A variety of life cycles have evolved among the multicellular algae The most complex life cycles include an alternation of generations, the alternation of multicellular haploid and diploid forms Heteromorphic generations are structurally different, while isomorphic generations look similar Oomycetes Water molds, white rusts, and downy mildews Once considered fungi Most are decomposers or parasites They have filaments (hyphae) that facilitate nutrient uptake Their ecological impact can be great, as in potato blight caused by Phytophthora infestans Rhizarians are a diverse group of protists defined by DNA similarities Cercozoans Include most amoeboid and flagellated protists with threadlike pseudopodia They are common in marine, freshwater, and soil ecosystems Most are heterotrophs, including parasites and predators 5

Foraminiferans Porous, generally multichambered shells, called tests Pseudopodia extend through the

endosymbiotic algae Radiolarians Marine protists called radiolarians have tests fused into one

through phagocytosis Red algae and green algae are the closest relatives of land plants Red algae

multicellular; the largest are seaweeds Red algae are the most abundant large algae in coastal

chlorophytes and charophyceans Charophytes are most closely related to land plants Most

6 Foraminiferans Porous, generally multichambered shells, called tests Pseudopodia extend through the pores in the test Foram tests in marine sediments form an extensive fossil record Many forams have endosymbiotic algae Radiolarians Marine protists called radiolarians have tests fused into one delicate piece, usually made of silica Radiolarians use their pseudopodia to engulf microorganisms through phagocytosis Red algae and green algae are the closest relatives of land plants Red algae Reddish in color due to an accessory pigment called phycoerythrin Red algae are usually multicellular; the largest are seaweeds Red algae are the most abundant large algae in coastal waters of the tropics Green algae Green algae are a paraphyletic group The two main groups are chlorophytes and charophyceans Charophytes are most closely related to land plants Most chlorophytes live in fresh water, although many are marine Other chlorophytes live in damp soil, as symbionts in lichens, or in snow 6

Unikonts include protists that are closely related to fungi and animals Amoebozoans Amoeba that have lobe- or tube-shaped, rather than

molds are brightly pigmented, usually yellow or orange At one point in the life cycle, plasmodial slime molds form a mass called a

cells are separated by their membranes Cells feed individually, but can aggregate to form a fruiting body Dictyostelium discoideum is an

freshwater and marine environments Most are heterotrophic and actively seek and consume bacteria and other protists Entamoebas Parasites

7 Unikonts include protists that are closely related to fungi and animals Amoebozoans Amoeba that have lobe- or tube-shaped, rather than threadlike, pseudopodia They include slime molds, gymnamoebas, and entamoebas Plasmodial slime molds Many species of plasmodial slime molds are brightly pigmented, usually yellow or orange At one point in the life cycle, plasmodial slime molds form a mass called a plasmodium that is not multicellular but has many diploid nuclei 1 mm 4 cm Cellular slime molds Form multicellular aggregates in which cells are separated by their membranes Cells feed individually, but can aggregate to form a fruiting body Dictyostelium discoideum is an experimental model for studying the evolution of multicellularity Gymnamoebas Common unicellular amoebozoans in soil as well as freshwater and marine environments Most are heterotrophic and actively seek and consume bacteria and other protists Entamoebas Parasites of vertebrates and some invertebrates Entamoeba histolytica causes amebic dysentery, the third-leading cause of human death due to eukaryotic parasites 7

8 Opisthokonts Include animals, fungi, as well as the protists Nucleariids, and Choanoflagellates Protists play key roles in ecological communities Protists are found in diverse aquatic environments Can play a variety of roles: Symbiotic (e.g., gut of termites) Parasitic (e.g., plasmodium) Producer (e.g., kelp) 8

BIOLOGY - CLUTCH CH.29 - PROTISTS.

BIOLOGY - CLUTCH CH.29 - PROTISTS. !! www.clutchprep.com Eukrayotic cells are large, have a nucleus, contain membrane-bound organelles, and use a cytoskeleton The nucleus is the synapomorphy that unifies eukaryotes Endosymbiotic theory