CHAPTER 29 LECTURE SLIDES Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Protists Chapter 29 Chapter 29

Eukaryotic Origins Eukaryotic cells differ from prokaryotes Presence of a cytoskeleton Compartmentalization (nucleus and organelles) Appearance of eukaryotes in microfossils occurred about 1.5 BYA

The nucleus and endoplasmic reticulum arose from infoldings of prokaryotic cell membrane

Many organelles evolved via endosymbiosis between an ancestral eukaryote and a bacterial cell Mitochondria Aerobic bacteria engulfed by larger bacteria

Brown algae engulfed red algae that already had chloroplasts Larger bacteria engulfed smaller photosynthetic bacteria Chloroplasts come from single line of cyanobacteria Hosts are not monophyletic Brown algae engulfed red algae that already had chloroplasts Secondary endosymbiosis

Endosymbiosis supported by DNA inside mitochondria and chloroplasts DNA similar to bacteria DNA in size and character Ribosomes inside mitochondria similar to bacterial ribosomes Chloroplasts and mitochondria replicate by binary fission – not mitosis

Defining Protists Most diverse of the four eukaryotic kingdoms United on the basis that they are not fungi, plants, or animals Vary considerably in every other aspect Unicellular, colonial, and multicellular groups Most are microscopic but some are huge All symmetries All types of nutrition

Protista is not monophyletic Paraphyletic Does not represent any evolutionary relationships Grouping 15 major protist phyla into 7 monophyletic groups 60 lineages are still not placed

Working model for protists classification

Cell surface Cysts Plasma membrane Extracellular material (ECM) in some Diatoms – Silica shells Cysts Dormant cell with resistant outer covering Used for disease transmission

Locomotion Flagella Cilia Pseudopodia (“false feet”) One or more Shorter and more numerous than flagella Pseudopodia (“false feet”) Lobopods – large, blunt Filopods – thin, branching Axopods – thin, long

Nutrition Phototrophs Heterotrophs Phagotrophs – Ingest particulate food matter Osmotrophs – Soluble food matter Mixotrophs are both phototrophic and heterotrophic

Asexual reproduction Sexual reproduction Typical mode of reproduction Some species have an unusual mitosis Mitosis – equal size daughter cells Budding – one daughter cell smaller Schizogony – cell division preceded by several nuclear divisions; produces several individuals Sexual reproduction May be obligate, or only under stress Meiosis is a major eukaryote innovation Union of haploid gametes which are produced by meiosis Advantage in allowing frequent genetic recombination

Multicellularity From single cells to colonies to true multicellularity Arisen multiple times Fosters specialization Few innovations have had as great an influence on the history of life

Diplomonads Unicellular Move with flagella 2 nuclei Giardia Degenerate mitochondria

Parabasalids Live in termite guts Trichomonas vaginalis – STD Host cellulose degrading bacteria Trichomonas vaginalis – STD Undulating membrane for locomotion Use flagella Lack mitochondria – derived trait

Euglenozoa Among the earliest eukaryotes to possess mitochondria 1/3rd have chloroplasts and are autotrophic May become heterotrophic in the dark Others lack chloroplasts and are heterotrophic All have a flexible pellicle No sexual reproduction

© Andrew Syred/Photo Researchers, Inc. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Euglena Two anterior (and unequal) flagella Attached at reservoir Contractile vacuoles – collect excess water Stigma – movement towards light Numerous small chloroplasts From ingestion of green algae Concept of a single Euglena genus is now being debated a. 6.5 µm © Andrew Syred/Photo Researchers, Inc.

Kinetoplastids 2nd major group in Euglenozoa Unique, single mitochondrion DNA maxicircles and minicircles Trypanosomes cause human diseases African sleeping sickness – tsetse fly Leishmaniasis – sand fly Chagas disease – skin contact with urine or blood of infected wild animal

Difficult to control because organisms repeatedly change their protective coat Release of sterilized flies Traps scented like cows but treated with insecticides Sequencing of genomes revealed core of common genes in all 3 – hope for single drug target

Alveolata Flattened vesicles called alveoli Dinoflagellates Apicomplexans Ciliates Common lineage despite diverse modes of locomotion

Dinoflagellates Photosynthetic, unicellular with flagella Live in aquatic environments Some are luminescent Do not appear to be directly related to any other phylum “Red tide” are “blooms” – fish, birds, and marine mammals may die from toxins DNA not complexed with histones

Apicomplexans Spore-forming animal parasites Apical complex is a unique arrangement of organelles at one end of the cell Enables the cell to invade its host Plasmodium causes malaria Complex life cycle – sexual, asexual, different hosts Eradication focused on eliminating mosquito vector, drug development, vaccines DDT-resistant mosquitoes

Other apicomplexans Gregarines Toxoplasma gondii Found in the intestines of arthropods, annelids, and mollusks Toxoplasma gondii Causes infections in humans with immunosuppression Can cross placental barrier to harm fetus

Ciliates 3rd group of apicomplexans Feature large numbers of cilia arranged in longitudinal rows or spirals around the cell Pellicle – tough but flexible outer covering 2 types of nuclei Micronucleus – without will reproduce asexually Macronucleus – essential for function Have two types of vacuoles Food vacuoles – digestion of food Contractile vacuoles – regulation of water balance

Conjugation Only different mating types can conjugate

Stramenopila Brown algae, diatoms, and oomycetes Very fine hairs on their flagella A few species have lost their hairs during evolution

Brown algae Not plants Conspicuous seaweeds of northern regions Life cycle involves alternation of generations Sporophyte – multicellular and diploid Gametophyte – multicellular and haploid Not plants

Diatoms Phylum Chrysophyta Photosynthetic, unicellular organisms Unique double shells made of silica Some move using raphes Two long grooves lined with vibrating fibrils

Oomycetes “Water molds” Either parasites or saprobes Were once considered fungi Motile zoospores with two unequal flagella Produced asexually Undergo sexual reproduction Found in water or on land Phytophthora infestans Irish potato famine (1845–1847) 400,000 people died

Rhodophyta Red algae range from microscopic to very large Lack flagella and centrioles Have accessory photosynthetic pigments within phycobilisomes Origin has been a source of controversy Tentatively, treated as a sister clade of Chlorophyta (green algae)

Choanoflagellida Most like common ancestor of all animals Single emergent flagellum, surrounded by funnel-shaped contractile collar Structure matched in sponges Use collar to feed on bacteria Have a surface tyrosine kinase receptor found in sponges

Protists Without a Clade Amoebas are paraphyletic Rhizopoda (True amoebas) Move by means of cytoplasmic projections called pseudopods

Actinopoda (Radiolarians) Glassy exoskeletons made of silica Needlelike pseudopods

Foraminifera Heterotrophic marine protists Pore-studded shells called tests, through which thin podia emerge Use podia for swimming and feeding Complex life cycles with haploid and diploid generations Limestones are rich in forams White Cliffs of Dover

Slime molds Were once considered fungi Include two lineages Plasmodial slime molds Huge, single-celled, multinucleate, oozing masses Cellular slime molds Single cells combine and differentiate, creating an early model of multicellularity

Plasmodial slime molds Stream along as a plasmodium Nonwalled, multinucleate mass of cytoplasm Form called feeding phase Ingests bacteria and other organic material When food or moisture is scarce, organism forms sporangia, where spores are produced

Cellular slime molds Important group for the study of cell differentiation because of their relatively simple developmental systems Individual organisms behave as separate amoebas Move through soil ingesting bacteria When food is scarce, organisms aggregate to form a slug Slug differentiates into a sorocarp