9/29/14 Biosc 41 Announcements 9/29 Review: History of Life v Quick review followed by lecture quiz (history & v How long ago is Earth thought to have formed? phylogeny) v What is thought to have been the first genetic material? v Lecture: Protists v Are we tetrapods? v Lab: Protozoa (animal-like protists) v Most atmospheric oxygen comes from photosynthesis v Lab exam 1 is Wed! (does not cover today’s lab) § Since many of the first organisms were photosynthetic (i.e. cyanobacteria), a LOT of excess oxygen accumulated (O2 revolution) § Some organisms adapted to use it (aerobic respiration) Review: History of Life Review: Phylogeny v Which organelles are thought to have originated as v Homology is similarity due to shared ancestry endosymbionts? v Analogy is similarity due to convergent evolution v During what event did fossils resembling modern taxa suddenly appear en masse? v A valid clade is monophyletic, meaning it consists of the ancestor taxon and all its descendants v How many mass extinctions seem to have occurred during v A paraphyletic grouping consists of an ancestral species and Earth’s history? Describe one? some, but not all, of the descendants v When is adaptive radiation likely to occur? v A polyphyletic grouping includes distantly related species but does not include their most recent common ancestor v Maximum parsimony assumes the tree requiring the fewest evolutionary events is most likely Quiz 3 (History and Phylogeny) BIOSC 041 1. How long ago is Earth thought to have formed? 2. Why might many organisms have evolved to use aerobic respiration? PROTISTS! Reference: Chapter 28 3. Which two organelles are thought to have originated as endosymbionts? 4. __________ is similarity due to shared ancestry, while __________ is similarity due to convergent evolution. 5. A valid clade is _____________, meaning it consists of the ancestor taxon and all its descendants. 1 9/29/14 Diplomonads Excavata Outline What is a Protist? Parabasalids Euglenozoans § Everything that is not Stramenopiles v General characteristics of protists something else Diatoms v Our understanding of the relationships among protist Golden algae § But definitely not an animal Brown algae “SAR” clade groups continues to change rapidly! Alveolates v The one-time kingdom of Dinoflagellates v One hypothesis divides all eukaryotes (including protists) Apicomplexans Protista has been abandoned Ciliates into four supergroups: Forams v Protists are now recognized as Rhizarians Cercozoans § Excavata polyphyletic Radiolarians § “SAR” clade § Some lineages of protists Archaeplastida Red algae Green § Archaeplastida recognized as kingdoms algae Chlorophytes Charophytes § v Protist remains the informal Unikonta Land plants Amoebozoans v Roles in Ecological Communities name for highlighted taxa v “Protozoa” are animal-like Slime molds § Producers Tubulinids Entamoebas protists Unikonta § Consumers Nucleariids Opisthokonts Fungi § Parasites & pathogens Choanoflagellates Animals The Protists exhibit more structural and functional Most protists are unicellular, and small… diversity than any other group of eukaryotes v Single-celled protists can be very complex, as all biological § Include unicellular, colonial, and multicellular taxa functions are carried out by organelles in each individual cell § Most range in size from <1-200 µm …but there are many exceptions… v The Protists also include colonial and multicellular taxa- particularly algae v Galatheammina (Xenophyophore) v Algae are considered protists because they don’t meet the v Benthic (deep sea) protozoan, ~10 cm in diameter complex tissue criteria of true plants v Single-celled(!!) § Range in size from 100’s um to 100’s meters (giant kelp) § “ruffled” surface increases surface area for gas/nutrient exchange 2 9/29/14 Nutritional and reproductive diversity Endosymbiosis in Eukaryotic Evolution v Protists owe their diversity to endosymbiosis- a unicellular v Nutrition organism engulfs another cell, which becomes an § Photoautotrophs endosymbiont and then an organelle in the host cell § Contain chloroplasts § Review: § Obtain energy from the sun and carbon from CO2 § Mitochondria evolved by endosymbiosis of an aerobic § Heterotrophs heterotrophic bacterium § Obtain both energy and carbon from organic molecules, § Chloroplasts evolved by endosymbiosis of absorbed from the environment or through ingestion of photosynthetic cyanobacterium other organisms v The plastid-bearing protists evolved into red and green algae § Mixotrophs (DNA of plastid genes in red algae and green algae closely resemble DNA of cyanobacteria) § Combine photosynthesis and heterotrophic nutrition v During eukaryotic evolution, red and green algae also v Reproduction underwent secondary endosymbiosis, in which they were § Sexual, asexual, or both! ingested by a heterotrophic eukaryote Figure 28.2 Five Supergroups of Diplomonads Excavata Plastid Eukaryotes Parabasalids Euglenozoans Stramenopiles Dinoflagellates Diatoms Golden algae v Our understanding of the Brown algae “SAR” clade Secondary Alveolates Dinoflagellates endosymbiosis relationships among protist Membranes Apicomplexans Apicomplexans are represented groups continues to change as dark lines in Ciliates Red alga the cell. rapidly Forams Cyanobacterium Rhizarians 1 2 Cercozoans 3 v One hypothesis divides all Radiolarians Primary eukaryotes (including protists) endosymbiosis Archaeplastida Stramenopiles Red algae Green into four supergroups algae Chlorophytes Heterotrophic Secondary Plastid Charophytes endosymbiosis eukaryote One of these Land plants membranes was Amoebozoans lost in red and Slime molds green algal Euglenids descendants. Tubulinids Secondary Entamoebas Unikonta endosymbiosis Nucleariids Green alga Opisthokonts Fungi Chlorarachniophytes Choanoflagellates Animals Supergroup #1: Excavates Excavata: Diplomonads and Parabasalids v These two groups lack plastids, have modified mitochondria, v Include protists with modified mitochondria and protists and most live in anaerobic environments with unique flagella v Diplomonads v The clade Excavata is characterized by its cytoskeleton § Have modified mitochondria called mitosomes v Some members have a feeding groove § Derive energy from anaerobic biochemical pathways v This diverse group includes § Have two equal-sized nuclei and multiple flagella § Diplomonads § Are often parasites, for example, Giardia intestinalis (also known as Giardia lamblia) § Parabasalids Diplomonads Excavata § Euglenozoans Parabasalids Euglenozoans SAR clade Archaeplastida Unikonta 3 9/29/14 Parabasalids Euglenozoans v Euglenozoa is a diverse clade that includes predatory v Have reduced mitochondria called hydrogenosomes heterotrophs, photosynthetic autotrophs, and parasites that generate some energy anaerobically v Distinguishing feature v Include Trichomonas vaginalis, the pathogen that § A spiral or crystalline rod of unknown function inside causes a type of vaginal infection in human females their flagella v This clade includes the § Kinetoplastids § Euglenids Euglenozoa - Kinetoplastids More about trypanosomes v Kinetoplastids are distinguished from other protozoa by the v Trypanosomes evade immune responses by switching surface kinetoplast- a single mitochondrion containing an organized proteins mass of DNA (kDNA) that comprises several copies of the v A cell produces millions of copies of a single protein mitochondrial genome v The new generation produces millions of copies of a v Include free-living consumers of prokaryotes in freshwater, different protein marine, and moist terrestrial ecosystems v These frequent changes prevent the host from developing v Also include some pathogens immunity § Trypanosoma, which causes sleeping sickness in humans § Another pathogenic trypanosome causes Chagas’ disease Euglenozoa - Euglenids Supergroup #2: SAR clade v Euglenids have one or two flagella that emerge from a v A highly diverse group of protists defined by DNA similarities pocket at one end of the cell v The “SAR” clade is a diverse monophyletic supergroup v Some species can be both autotrophic and heterotrophic named for the first letters of its three major clades Stramenopiles, Alveolates, and Rhizarians v This group is the most controversial of the four supergroups (sometimes split to give 5 subgroups) v Stramenopiles covered in Biosc 42 Excavata Diatoms Golden algae Stramenopiles Brown algae SAR clade Dinoflagellates Apicomplexans Alveolates Ciliates Forams Cercozoans Rhizarians Radiolarians Archaeplastida Unikonta 4 9/29/14 Alveolata Dinoflagellates v Dinoflagellates have two flagella and each cell is reinforced v Members of the clade Alveolata have membrane-bounded sacs (alveoli) just under the plasma membrane by cellulose plates v They are abundant components of both marine and v The function of the alveoli is unknown freshwater phytoplankton v The alveolates include v They are a diverse group of aquatic phototrophs, § Dinoflagellates mixotrophs, and heterotrophs § Apicomplexans v Toxic “red tides” are caused by dinoflagellate blooms § Ciliates Apicomplexans More about Apicomplexans v Apicomplexans are parasites of animals, and some cause serious human diseases v Responsible for some of the most serious human disease – Malaria § No movement, no free-living forms (Plasmodium), Toxoplasmosis (obligate parasites) v Plasmodium requires both § Complex intracellular structures and mosquitoes and humans to lifecycles (spread through host as complete its life cycle infectious cells called sporozoites) v ~900,000 people die each year § One end,