The Origin and Diversification of Eukaryotes Chapter 20 The Origin and Diversification of Eukaryotes

20.1 Eukaryotes Acquired Features from Both Archaea and Bacteria Eukaryotes that are not plants, animals, or fungi are called protists Scientists believe came from the fusion of prokaryotes due to endosymbiosis

Eukaryotes arose in several steps The origin of a flexible cell surface The origin of a cytoskeleton The origin of a nuclear envelope The appearance of digestive vacuoles The acquisition of certain organelles via endosymbioisis

http://learn.genetics.utah.edu/content/begin/cells/organelles/

Protista Video

20.2 Major Lineages of Eukaryotes Diversified in the Precambrian

Characteristics of the Protists: Range from unicelluar to multicellular All are eukaryotic Some free-living and some symbionts Nearly all are aerobic Some are photoautotrophs with chloroplasts; others are heterotrophs others combine photosynthesis and eating

Characteristics of Protists (continued) Most have cilia or flagella at some time in their life cycles All can reproduce asexually; others can also reproduce sexually Mitosis occurs in most Some have elaborate cells even though unicellular; e.g., Paramecium

Alveolates have sacs under their plasma membranes Alveolates-possess sacs called alveoli under their membranes which play a role in supporting the cell surface All are unicellular and most are photosynthetic Dinoflagellates, Apicomplexans, and Ciliates

Alveolates http://pinkava.asu.edu/starcentral/microscope/msr/rawdata/viewable/alveolates_1158459360__84w.jpg

Dinoflagellates Have protective cellulose plates Most have two flagella—one in a longitudinal groove with distal end free and the other in a transverse groove that encircles the organism Extremely numerous in the oceans Most are heterotrophic

Dinoflagellates continued Some live as symbionts in invertebrates; e.g. coral 2 genera cause “red tides” and produce a neurotoxin that can kill fish and paralytic shellfish poisoning in humans

Figure 28.12 A dinoflagellate

Figure 28.12x1 Dinoflagellate

Figure 28.12x2 Swimming with bioluminescent dinoflagellates

Apicomplexans Derive there name from the apical complex which is a mass of organelles contained in the apical end (Helps invade host’s tissues) Helps Plasmodium invade tissues to causes malaria Plasmodium and Toxoplasma are parasites

Apicomplexans

Ciliates Named for their hairlike cilia which a like flagella but shorter Have two types of nuclei Almost all are heterotrophic Most common is the Paramecium

Ciliates Contractile Vacuole-A specialized vacuole that collects excess water taken in by osmosis, then contracts to expel the water from the cell Digestive Vacuole-An organelle specialized for digesting food ingested by endocytosis

Figure 28.14c Ciliates: Paramecium

Figure 28.14x Ciliates: Stentor (left), Paramecium (right)

Figure 28.15x Paramecium conjugating

Paramecium

Excavates began to diversify about 1.5 billion years ago Lack mitochondria and lost them as they evolved Shows eukaryotic life is possible without a mitochondria Include: Diplomonads and Parabasalids, Heteroloboseans, and Euglenids and Kinetoplastids

Excavates http://cnx.org/content/m44617/latest/Figure_23_03_02.jpg

Diplomonads and Parabasalids Unicellular and lack mitochondria Causes contaminated water and diseases in humans

Diplomonads and Parabasalids

Heteroloboseans Has an amoeboid body and can turn into a life cycle with a flagella http://pinkava.asu.edu/starcentral/microscope/msr/rawdata/files/trimastigamoeba_ihz.gif

Euglenids and Kinetoplastids Unicellular, freshwater organisms Some have chloroplasts; the rest ingest food If grown in darkness, lose chloroplasts and become heterotrophic Have stored food in pyrenoid in form of a carbohydrate polymer paramylon Bounded by a pellicle which is flexible to allow changes in shape

Figure 28.03x Euglena

Figure 28.3 Euglena: an example of a single–celled protist

Figure 28.11x Trypanosoma, the kinetoplastid that causes sleeping sickness

Stramenopiles typically have two unequal flagella, one with hairs Include the diatoms and the brown algae which are photosynthetic Also Oomycetes which are not http://cnx.org/content/m44617/latest/Figure_23_03_08.jpg

Diatoms Most numerous unicellular algae in oceans and are abundant in fresh water Have cell walls of silica and many geometric shapes Reproduce both sexually and asexually

Figure 28.17 Diatoms: Diatom diversity (left), Pinnularia (left)

Figure 28.17x Diatom shell

Brown algae Both brown and golden brown algae have chlorophylls a and c Range from small forms with simple filaments to large multicellular forms we call seaweeds Provide food and habitat for marine organisms and are harvested for human food and fertilizer

Figure 28.1d Too diverse for one kingdom: Australian bull kelp (Durvillea potatorum)

Figure 28.20x2 Kelp forest

Figure 28.20x1 Kelp forest

Water molds - oomycetes Usually live in water and parasitize fish Others live on land and parasitize insects and plants One species caused Irish potato famine in 1840s Have cell walls of cellulose; fungi have chitin Saprobic-feed on dead organic matter

Figure 28.16 The life cycle of a water mold (Layer 3)

Figure 28.16x2 Water mold: Oogonium

Figure 28.x2 Powdery mildew

Rhizaria typically have long thin pseudopods Include Cercozoans, Foraminiferans, and Radiolarians Unicellular and mostly aquatic Pseudopods allow for movement

Cercozoans Very diverse group with many forms and habitats https://ncma.bigelow.org/media/catalog/category/cercozoa.png

Foraminiferans Secrete external shells of calcium carbonate Some live as plankton and others live on the seas floor Form much of the world’s limestone

http://gallery.usgs.gov/images/03_27_2014/gkb4Frq11X_03_27_2014/large/Animals_SignsStructuresEtc_Structures_00047.jpg

Figure 28.28 Foraminiferan

Radiolarians Have thin pseudopods which are structured with microtubules Help them stay afloat in the ocean Well know for when they shed their endoskeletons

http://micro. magnet. fsu. edu/micro/gallery/radiolarians/radiohead http://micro.magnet.fsu.edu/micro/gallery/radiolarians/radiohead.jpg

Figure 28.27x Radiolarian skeleton

Figure 28.27 Actinopods: Heliozoan (left), radiolarian (right)

Amoebozoans use lobe-shaped pseudopods for locomotion Three groups loboseans, plasmodial slime molds and cellular slime molds http://upload.wikimedia.org/wikipedia/commons/b/b3/Chaos_carolinense.jpg

Loboseans Small Amoebozoans that feed by phagocytosis engulfing with the pseudopod Live in the bottom of lakes and ponds Most are predators, parasites, or scavengers

Figure 28.1a Too diverse for one kingdom: Amoeba proteus, a unicellular "protozoan"

Figure 28.26 Use of pseudopodia for feeding

Plasmodial (acellular) Slime Molds Consist of a multinucleated mass, a plasmodium Phagocytizes decaying plant material Develops sporangia during unfavorable conditions Coenocyte-many nuclei enclosed in a single plasma membrane

Figure 28.29x1 Plasmodial slime mold

Figure 28.1c Too diverse for one kingdom: a slime mold (Physarum polychalum)

Figure 28.29 The life cycle of a plasmodial slime mold, such as Physarum

Figure 28.29x2 Slime mold Sporangia

Cellular Slime Molds Consist of individual ameboid cells During unfavorable conditions cells aggregate into pseudoplasmodium Sporangium produces spores that release haploid ameboid cells

Figure 28.30 The life cycle of a cellular slime mold (Dictyostelium)

Figure 28.30x1 Dictyostelium life cycle

Slime Mold Video The difference between Plasmodial or acellular slime molds and cellular slime molds is that cellular slime molds have separated nuclei. Plasmodial slime molds create a mass with multiple nuclei

20.3 Protists reproduce sexually and asexually Protists produce asexually by: Binary fission-one cell into two Multiple fission- one cell into multiple Budding-outgrowth of a new cell from a previous one Sporulation-formation of a spore that is able to grow into a new organism Clonal lineages-Asexually reproduced groups of nearly identical organisms

Some protists reproduce without sexual reproduction Parmecia go through the process of conjugation This is when two individuals line up tightly against each other and fuse Genetic material is exchanged creating a micronucleus Meiosis and mitosis also take place Not a form of reproduction just a sexual process of genetic recombination

Figure 28.15x Paramecium conjugating

Some protist life cycles feature alternation of generations Alternation of generations-The succession of multicellular haploid and diploid phases in some sexually reproducing organisms The haploid organism, the diploid organism, or both may also reproduce asexually

Morphology may or not different in alternation of generations Heteromorphic-the two generations differ morphologically Isomorphic-they do not differ

http://www.quia.com/files/quia/users/lmcgee/protistpictures/AP_Chpt_28_Protists/Alternation-of-generations-.gif

The gamete producing generation does not produce gametes by meiosis because it is haploid Specialized cells of the diploid spore-producing organism, called sporocytes, divide meiotically to produce four haploid spores Gametes can only produce new organisms by fusing with other gametes

http://plantphys.info/organismal/lechtml/images/achlyaoogonia.jpg

20.4 Protists Are Critical Components of Many Ecosystems http://aquabella4aquariums.com/blog/wp-content/uploads/2013/06/ecosystem101.png

Phytoplankton are primary producers http://w3.shorecrest.org/~Lisa_Peck/MarineBio/syllabus/ch11_ecosystems/ecosystem_wp/neriticzone_jonathan_wade/energy_pyramid.gif

Some microbial eukaryotes are deadly http://4.bp.blogspot.com/-R-dhf4iQooU/UguBWA19wVI/AAAAAAAABS4/YaR6AYejpy4/s1600/ANOPHELES+MOSQUITOES.jpg

Some microbial eukaryotes are endosymbionts

Coral Bleaching (Protists dying) http://media.treehugger.com/assets/images/2011/10/bleached-coral-photo-0001.jpg

We rely on the remains of ancient marine protists http://www.agiweb.org/education/energy/images/gasformation.png