l The origin of Eukaryotes
l The classification of Protists
l 3 of the more primitive groups of Protists
– Archezoa
– Euglenozoa
– Alveolates
3 things that you should watch for in this lecture
l The way that eukaryotes have evolved from primitive ancestors
l The way that the organisms are classified and the factors that affect their classification
l The ways that protists can affect public health
 
Evolution of eukaryotes by serial endosymbiosis
l Nuclear membrane and endoplasmic reticulum formed from invagination of plasma membrane akin to phagocytosis
l Inclusion of organelles from phagocytosis of aerobic bacterium / cyanobacterium
l The origin of microtubule structures (flagellae, cilia, cytoskeleton) is unknown
Protists
l Ingestive        (animal-like); protozoa
l Absorptive (fungus-like)
l Photosynthetic (plant-like); alga
The Endosymbionic Theory
l Mitochondria and chloroplasts were formerly from small prokaryotes living within larger cells (Margulis)
Protist Systematics & Phylogeny, I
l 1- Groups lacking mitochondria; early eukaryotic link; Giardia (human intestinal parasite; severe diarrhea); Trichomonas (human vaginal infection)
l 2- Euglenoids; autotrophic & heterotrophic flagellates; Trypanosoma (African sleeping sickness; tsetse fly)
 
l Alveolata: membrane-bound cavities (alveoli) under cell surfaces; dinoflagellates (phytoplankton); Plasmodium (malaria);    ciliates (Paramecium)
 
 
l Stamenophila: water molds/mildews and heterokont (2 types of flagella) algae; numerous hair-like projections on the flagella; most molds are decomposers and mildews are parasites; algae include diatoms, golden, and brown forms
 
l Rhodophyta: red algae; no flagellated stages; phycobilin (red) pigment
l Chlorophyta: green algae; chloroplasts; gave rise to land plants; volvox, ulva
 
l Affinity uncertain:
l Rhizopods: unicellular with pseudopodia; amoebas
l Actinopods: ‘ray foot’ (slender pseudopodia; heliozoans, radiolarians
 
l Mycetozoa: slime molds (not true fungi); use pseudopodia for locomotion and feeding; plasmodial and cellular slime molds
 
1. Nucleus formation
1. Nucleus formation
2. Origin of organelles
Features of ‘Protists’
l All eukaryotes
l Mostly unicellular
l ‘Primitive’ and thought to have diverged early from a ‘universal ancestor’
l Very diverse
Types of ‘Protist’
Evolutionary relations
l For many years, all organisms that did not conveniently fit into other groups were placed into the ‘Protists’.
l Classification is in a very active and dynamic state.
l Recently, molecular phylogeny based on similarity in DNA + electron microscopy has led to reclassification to give MONOPHYLETIC groups - organisms are grouped if they have a common ancestor.
 
 
Cellular Tree of Life
 
 
Summary of evolutionary relations
Ways of classifying ‘Protists’
ARCHEZOA (from Greek Arkhaios meaning ancient)
l Considered to be the most primitive of all eukaryotes
l No mitochondria (some engulf bacteria)
l Mostly parasitic (e.g. Giardia)
l 3 Sub-groups
– Diplomonads (includes Giardia)
– Trichomonads (e.g. Trichomonas)
– Microsporidians
Giardia
l An important parasite
l Transmitted by both water and animals
l Probably the most important source of holiday diarrhea
Trichomonas
l An STD
EUGLENOZOA
l Flagellates
l 2 sub-groups

– euglenoids
Photosynthetic but may be
heterotrophic or mixotrophic
– Kinetoplastids
Symbiotic or parasitic e.g. Trypanosoma, Leishmania
 
Trypanosoma
l Causes sleeping sickness in cattle and man in Africa transmitted by the Tsetse Fly
l In Americas, Chagas disease
 
Chagas disease / Sleeping Sickness
 
l What're the symptoms of sleeping sickness?
l Symptoms of sleeping sickness begin with fever, headaches, and joint pains. If untreated, the disease slowly overcomes the defences of the infected person, and symptoms spread to anaemia, endocrine problems, and cardiovascular and kidney disorders. The disease then enters a neurological phase when the parasite passes through the blood-brain barrier.
 
l The symptoms of the second phase is what gives the disease its name: besides confusion and reduced coordination, the sleep cycle is disturbed with bouts of lethargy punctuated with manic periods progressing to daytime somnolence and nighttime insomnia. Without treatment, the disease is fatal, with progressive mental deterioration leading to coma and death. Damage caused in the neurological phase can be irreversible.
 
l Life cycle involves biting/sucking insects
Leishmania
l The life cycles of members of the genus involve a vertebrate host (e.g., the human) and a vector (a sand fly) that transmits the parasite between vertebrate hosts
 
l Leishmania systemic disease, called visceral leishmaniasis, can have fatal complications. When introduced into the body by the bite of a sandfly, the parasite migrates to the bone marrow, spleen, and lymph nodes. The parasites damage the immune system by decreasing the numbers of disease-fighting cells.
 
l Systemic infection in children usually begins suddenly with vomiting, diarrhea, fever, and cough. In adults, fever for 2 weeks to 2 months is accompanied by nonspecific symptoms, such as fatigue, weakness, and loss of appetite. Weakness increases as the disease progresses.
Cutaneous Leishmaniasis
ALVEOLATA
l All have small membrane bound cavities (Alveoli) beneath the cell surface.
l 3 subgroups
l Ciliates
l Apicomplexans
l Dinoflagellates
Ciliates
l All have cilia for locomotion and feeding
l Reproduce by binary fission
Trichodina sp.
l This genus contains many species, perhaps as many as 200, most of which are found as commensals or facultative or obligate parasites on aquatic invertebrates, fish,
l and amphibians.
Apicomplexans (Sporozoa)
l All parasites of animals
l All have a complex at the apex of the cell for penetrating host tissues (Apicomplex)
l ‘Relict’ plastids possibly related to dinoflagellates with 4 bounding membranes
l Plasmodium falciparum
l Pneumocystis carinii (Pneumonia)
l Toxoplasma gondii (toxoplasmosis)
l Cryptosporidium parvum (cryptosporidosis)
Apicoplast (plastid of Apicomplexan)
l 4 membranes
l Genome of circular plasmid
l Smallest genome of any plastid (35kb)
l Codes for a number of genes
l Provides a means of attacking the parasite
Malaria - Plasmodium/mosquito
 
l Malaria causes a flu-like illness and these would include
l fever
l rigors
l headaches
l sweating
l tiredness
l myalgia (limbs and back)
l abdominal pain
l diarrhea
l loss of appetite
l orthostatic hypotension
l nausea
l slight jaundice
l cough
l enlarged liver and spleen (sometimes not palpable)
l vomiting
 
Malaria - infection with an Apicomplexan, Plasmodium
Dinoflagellates
l Abundant components of the phytoplankton
l Blooms cause red tides in coastal waters
l Can be an important symbiont in coral reefs
 
Protists
 
l Overview: A World in a Drop of Water
l Even a low-power microscope
– Can reveal an astonishing menagerie of organisms in a drop of pond water
 
l These amazing organisms
– Belong to the diverse kingdoms of mostly single-celled eukaryotes informally known as protists
l Advances in eukaryotic systematics
– Have caused the classification of protists to change significantly
 
l Protists are an extremely diverse assortment of eukaryotes
l Protists are more diverse than all other eukaryotes
– And are no longer classified in a single kingdom
l Most protists are unicellular
– And some are colonial or multicellular
 
l Protists, the most nutritionally diverse of all eukaryotes, include
– Photoautotrophs, which contain chloroplasts
– Heterotrophs, which absorb organic molecules or ingest larger food particles
– Mixotrophs, which combine photosynthesis and heterotrophic nutrition
 
l Protist habitats are also diverse in habitat
• And including freshwater and marine species
 
l Reproduction and life cycles
– Are also highly varied among protists, with both sexual and asexual species
 
l A sample of protist diversity
 
l A sample of protist diversity
Endosymbiosis in Eukaryotic Evolution
l There is now considerable evidence
– That much of protist diversity has its origins in endosymbiosis
 
l The plastid-bearing lineage of protists
– Evolved into red algae and green algae
l On several occasions during eukaryotic evolution
– Red algae and green algae underwent secondary endosymbiosis, in which they themselves were ingested
 
l Diversity of plastids produced by secondary endosymbiosis
 
l : Diplomonads and parabasalids have modified mitochondria
l A tentative phylogeny of eukaryotes
– Divides eukaryotes into many clades
 
l Diplomonads and parabasalids
– Are adapted to anaerobic environments
– Lack plastids
– Have mitochondria that lack DNA, an electron transport chain, or citric-acid cycle enzymes
Diplomonads
l Diplomonads
– Have two nuclei and multiple flagella
Parabasalids
l Parabasalids include trichomonads
– Which move by means of flagella and an undulating part of the plasma membrane
 
l Euglenozoans have flagella with a unique internal structure
l Euglenozoa is a diverse clade that includes
– Predatory heterotrophs, photosynthetic autotrophs, and pathogenic parasites
 
l The main feature that distinguishes protists in this clade
– Is the presence of a spiral or crystalline rod of unknown function inside their flagella
Kinetoplastids
l Kinetoplastids
– Have a single, large mitochondrion that contains an organized mass of DNA called a kinetoplast
– Include free-living consumers of bacteria in freshwater, marine, and moist terrestrial ecosystems
 
l The parasitic kinetoplastid Trypanosoma
– Causes sleeping sickness in humans
Euglenids
l Euglenids
– Have one or two flagella that emerge from a pocket at one end of the cell
– Store the glucose polymer paramylon
Phylum Euglenophyta
l The Euglenoids
– Spindle-shaped.
– No cell wall, thus changes shape as it moves.
• Sub-membrane strips and membrane form pellicle.
– Contains gullet.
– Contains red eyespot.
– Reproduction by cell division.
 
 
l Alveolates have sacs beneath the plasma membrane
l Members of the clade Alveolata
– Have membrane-bounded sacs (alveoli) just under the plasma membrane
Dinoflagellates
l Dinoflagellates
– Are a diverse group of aquatic photoautotrophs and heterotrophs
– Are abundant components of both marine and freshwater phytoplankton
MARINE PLANTS
Dinophyta /Pyrrhophyta or the Dinoflagellates Mostly unicellular with 2 unequal flagella , one that wraps around a groove in the middle of the cell, and the other that trails free, and include the non-motile zooxanthellae (found in corals).
The are most abundant in warm waters and second to diatoms in cold water.
Phylum Dinophyta
l The Dinoflagellates
– Unicellular
– Contain two flagella.
• One trails behind the cell.
• Other encircles the cell at right angles.
– Most have disc-shaped chloroplasts.
• Contain xanthophyll pigments.
– Many have tiny projectiles.
– Many types of toxins produced. (Red Tides)
Dinoflagellates
MARINE PLANTS
Characteristics of Dinoflagellates
1. Most are marine
2. Chlorophyll a, c, peridinin. Starch, oils , but can ingest food stuffs
3. Distinctive flagella pattern
4. Some without walls (naked) and others with walls (Armor) with cellulosic plates fitting together like armor which may have spines,
 
 
 
MARINE PLANTS
5. Half are colorless, some heterotrophic, sparophitic, phagocytic, parasitic and some photosynthetic. It is thought that through
evolution they have gained the ability to function as primary producers by "capturing" and using chloroplasts from other algae.
6. some bioluminescent
MARINE PLANTS
7. some responsible for red tides and 20 spp.. secrete toxins. They reproduce by simple cell division and form blooms that often color the water red, reddish-brown, yellow or unusual shades.
MARINE PLANTS
a. all toxic ones are photosynthetic
b. all are estuarine or neritic forms
c. all probably produce benthic, sexual resting stages
d. all capable of producing monospecific blooms (suggest competitive advantages through exclusion
 
MARINE PLANTS
e. all produce bioactive-watersoluable or lipid soluble toxins that are hemolytic, or neurotoxic in activity. (NSP, PSP, Dsp)
MARINE PLANTS
The Zooxanthellae are a variety of dinoflagellates which have developed a close association with an animal host. The hosts range from sponges to giant clams but the most important are the ones in the stony corals.
They help fix carbon through photosynthesis, release organic matter to be used by the coral, help in formation of the coral skeleton.
MARINE PLANTS
It was once believed that all zooxanthellae were the same species, Symbiodinium microadriaticum (Rowan and Powers, 1991). However, recently, zooxanthellae of various corals have been found to belong to at least 10 different algal taxa.
 
l Each has a characteristic shape
– That in many species is reinforced by internal plates of cellulose
l Two flagella
– Make them spin as they move through the water
 
l Rapid growth of some dinoflagellates
– Is responsible for causing “red tides,” which can be toxic to humans
Apicomplexans
l Apicomplexans
– Are parasites of animals and some cause serious human diseases
– Are so named because one end, the apex, contains a complex of organelles specialized for penetrating host cells and tissues
– Have a nonphotosynthetic plastid, the apicoplast
 
l Most apicomplexans have intricate life cycles
– With both sexual and asexual stages that often require two or more different host species for completion
 
Ciliates
l Ciliates, a large varied group of protists
– Are named for their use of cilia to move and feed
– Have large macronuclei and small micronuclei
 
l The micronuclei
– Function during conjugation, a sexual process that produces genetic variation
l Conjugation is separate from reproduction
– Which generally occurs by binary fission
 
l Exploring structure and function in a ciliate
 
 
l : Stramenopiles have “hairy” and smooth flagella
l The clade Stramenopila
– Includes several groups of heterotrophs as well as certain groups of algae
 
l Most stramenopiles
– Have a “hairy” flagellum paired with a “smooth” flagellum
Oomycetes (Water Molds and Their Relatives)
l Oomycetes
– Include water molds, white rusts, and downy mildews
– Were once considered fungi based on morphological studies
 
l Most oomycetes
– Are decomposers or parasites
– Have filaments (hyphae) that facilitate nutrient uptake
 
 
l The ecological impact of oomycetes can be significant
– Phytophthora infestans causes late blight of potatoes
Diatoms
l Diatoms are unicellular algae
– With a unique two-part, glass-like wall of hydrated silica
 
l Diatoms are a major component of phytoplankton
– And are highly diverse
Phylum Chromophyta
l The Diatoms (Bacillariophyceae)
– Among best known and economically most important members of this phylum.
• Mostly unicellular
– Occur in both fresh and salt water.
• Particularly abundant in colder marine habitats.
MARINE PLANTS
lDiatom Characteristics
l1. Usually unicellular but chains do occur
l2. Pigments chlorophyll. a & c and fucoxanthin (gold/brown)
l3. Food reserve is chrysolaminarin and oils (buoyant)
l4. Only flagellate cells in reproduction (uniflagellate.)
MARINE PLANTS
l5. Walls made of glass called frustule.
l6. Looks like petri dish
7. Two symmetries..radial and bilateral which divide diatoms into 2 sub-divisions..Centric & Pennates
 
 
 
 
 
 
MARINE PLANTS
Reproduction...valve to valve...one product of the division retains the parental epivalve (top) and the other the parental hypovalve (bottom) which results in the bottom being slightly smaller than the parent because a new inside always grows back.
Reproduction in Diatoms
 
MARINE PLANTS
Continued vegetative reproduction reduces the size until it gets to its smallest size and this diploid cell produces gametes which fuse to form a full size zygote. Only the small cells will undergo sexual reproduction and if they get too small, they can't even do that.
 
 
 
l Accumulations of fossilized diatom walls
– Compose much of the sediments known as diatomaceous earth
Golden Algae
l Golden algae, or chrysophytes
– Are named for their color, which results from their yellow and brown carotenoids
l The cells of golden algae
– Are typically biflagellated, with both flagella attached near one end of the cell
Phylum Cryptophyta
l The Cryptomonads
– Asymmetrical, unicellular marine and freshwater algae with two flagella.
• Single two-lobed chloroplast with starch granules surrounding a central pyrenoid.
• Distinctive nucleomorph
• Gullet
• Ejectosomes
• Reproduction by mitosis
Cryptomonas
 
l Most golden algae are unicellular
– But some are colonial
Brown Algae
l Brown algae, or phaeophytes
– Are the largest and most complex algae
– Are all multicellular, and most are marine
 
l Brown algae
– Include many of the species commonly called seaweeds
l Seaweeds
– Have the most complex multicellular anatomy of all algae
 
l Kelps, or giant seaweeds
– Live in deep parts of the ocean
 
 
 
 
 
 
 
 
 
 
Human Uses of Seaweeds
l Many seaweeds
– Are important commodities for humans
– Are harvested for food
Alternation of Generations
l A variety of life cycles
– Have evolved among the multicellular algae
l The most complex life cycles include an alternation of generations
– The alternation of multicellular haploid and diploid forms
 
l The life cycle of the brown alga Laminaria
 
 
l Cercozoans and radiolarians have threadlike pseudopodia
l A newly recognized clade, Cercozoa
– Contains a diversity of species that are among the organisms referred to as amoebas
l Amoebas were formerly defined as protists
– That move and feed by means of pseudopodia
l Cercozoans are distinguished from most other amoebas
– By their threadlike pseudopodia
Foraminiferans (Forams)
l Foraminiferans, or forams
– Are named for their porous, generally multichambered shells, called tests
 
l Pseudopodia extend through the pores in the test
l Foram tests in marine sediments
– Form an extensive fossil record
Radiolarians
l Radiolarians are marine protists
– Whose tests are fused into one delicate piece, which is generally made of silica
– That phagocytose microorganisms with their pseudopodia
 
l The pseudopodia of radiolarians, known as axopodia
– Radiate from the central body
 
l : Amoebozoans have lobe-shaped pseudopodia
l Amoebozoans
– Are amoeba that have lobe-shaped, rather than threadlike, pseudopodia
– Include gymnamoebas, entamoebas, and slime molds
Gymnamoebas
l Gymnamoebas
– Are common unicellular amoebozoans in soil as well as freshwater and marine environments
 
l Most gymnamoebas are heterotrophic
– And actively seek and consume bacteria and other protists
Entamoebas
l Entamoebas
– Are parasites of vertebrates and some invertebrates
l Entamoeba histolytica
– Causes amebic dysentery in humans
Slime Molds
l Slime molds, or mycetozoans
– Were once thought to be fungi
l Molecular systematics
– Places slime molds in the clade Amoebozoa
Plasmodial Slime Molds
l Many species of plasmodial slime molds
– Are brightly pigmented, usually yellow or orange
 
 
l The plasmodium
– Is undivided by membranes and contains many diploid nuclei
– Extends pseudopodia through decomposing material, engulfing food by phagocytosis
Cellular Slime Molds
l Cellular slime molds form multicellular aggregates
– In which the cells remain separated by their membranes
 
Phylum Myxomycota
l The Plasmodial Slime Molds
– Totally without chlorophyll and are incapable of producing their own food.
• Distinctly animal-like during much of life cycle, but fungus-like during reproduction.
– Plasmodium converts into separate small sporangia (each containing spores) during times of significant environmental changes.
Phylum Dictyosteliomycota
l The Cellular Slime Molds
– About two dozen species of cellular slime molds are not closely related to the other slime molds.
• Individual amoebalike cells feed independently, dividing and producing separate new cells periodically.
– Human and Ecological Relevance
• Break down organic particles to simpler substances.
Phylum Oomycota
l The Water Molds
– Often found on dead insects.
– Range in form from single spherical cells to branching, threadlike, coenocytic hyphae.
• Coenocytic hyphae may form large thread masses (mycelia).
 
 
l Dictyostelium discoideum
– Has become an experimental model for studying the evolution of multicellularity
 
 
l Green was the dominant color for plants both on land and in the ocean until about 250 million years ago when changes in the ocean's oxygen content - possibly sparked by a cataclysmic event - helped bring basic ocean plants with a red color to prominence - a status they retain today
 
l Studying ancient fossils plus current species of microscopic ocean plants called phytoplankton, the scientists found evidence that a "phytoplankton schism" took place after a global ocean oxygen depletion killed 85 percent of the organisms living in the ocean about 250 million years ago at the end of the Permian era. "This paved the way for the evolution of red phytoplankton,"
 
l "Plants on land are green, and they inherited the cell components that gave them a green color about 400 million years ago," Falkowski said. "But most of plants or phytoplankton in the ocean are red - they inherited their pigments about 250 million years ago.
 
l This suggests that a global ocean oxygen depletion changed the chemistry of the ocean and selected for red phytoplankton. The ocean has been dominated by the red line ever since."
 
 
l Red algae and green algae are the closest relatives of land plants
l Over a billion years ago, a heterotrophic protist acquired a cyanobacterial endosymbiont
– And the photosynthetic descendants of this ancient protist evolved into red algae and green algae
Red Algae
l Red algae are reddish in color
– Due to an accessory pigment call phycoerythrin, which masks the green of chlorophyll
 
l Red algae
– Are usually multicellular; the largest are seaweeds
– Are the most abundant large algae in coastal waters of the tropics
MARINE PLANTS
lRed Algae
lRhodophyta has more species of these than green and brown combined.
lIt has the highest commercial value, and don't get as large as brown algae.
•absence of flagellate stages
•presence of other pigments mainly phycobilins
Phylum Rhodophyta
l The Red Algae
– Most species are seaweed.
• Tend to occur in warmer and deeper waters than brown algae.
– Most are filamentous.
– Relatively complex life cycle involving three types of thallus structures.
– Colors mostly due to phycobilins.
– Numbers of species produce agar.
 
MARINE PLANTS
•Floridean starch as food reserve (scattered throughout cells)
•Existence of special female cells (carpogonia) and male gametes (called spermatia) for sexual reproduction.
•Cell walls with inner rigid component and outer mucilage or slime layer. This is like the alginates and very valuable.
 
MARINE PLANTS
They can also deposit calcium carbonate (lime) into the walls of some species (Coralline algae) (Coralline algae)
 
 
 
 
 
 
 
 
 
 
Green Algae
l Green algae
– Are named for their grass-green chloroplasts
– Are divided into two main groups: chlorophytes and charophyceans
– Are closely related to land plants
Phylum Chlorophyta
l The Green Algae
– Includes about 7,500 species that occur in a rich variety of forms and occur in diverse, widespread habitats.
• Greatest variety found in freshwater lakes, ponds, and streams.
• Most have a single nucleus.
• Most reproduce both sexually and asexually.
MARINE PLANTS
Chlorophyta..few marine planktonic reps. but lots of macroscopic, benthic types
Phylum Chlorophyta
l Chlamydomonas
– Common inhabitant of freshwater pools.
– Pair of whip-like flagella on one end pull the cell through the water.
– Single, cup-shaped chloroplast with one or two pyrenoids inside.
• Proteinaceous structures thought to contain starch synthesis enzymes.
Chlamydomonas
Chlamydomonas
l Asexual Reproduction
– Nucleus divides by mitosis, and cell contents become two daughter cells within the cellulose wall.
• Develop flagella and swim away.
Sexual Life Cycle of Chlamydomonas
Sexual Life Cycle of Chlamydomonas
Phylum Chlorophyta
l Ulothrix
– Thread-like alga.
• Single row of cylindrical cells forming a filament.
– Basal cell functions as a holdfast.
 
Ulothrix Life Cycle
Ulothrix Life Cycle
Phylum Chlorophyta
l Spirogyra (Watersilk)
– Common freshwater algae consisting of unbranched filaments of cylindrical cells.
• Frequently float in masses at the surface of quiet waters.
– Asexual Reproduction
• Fragmentation of existing filaments.
– Sexual Reproduction
• Papillae fuse and form conjugation tubes.
Spirogyra Sexual Reproduction
Phylum Chlorophyta
l Oedogonium
– Epiphytic filamentous green alga.
• Each cell contains a large, netlike chloroplast that rolls and forms a tube around and toward the periphery of each protoplast.
 
 
 
 
l Most chlorophytes
– Live in fresh water, although many are marine
l Other chlorophytes
– Live in damp soil, as symbionts in lichens, or in snow
 
l Chlorophytes include
– Unicellular, colonial, and multicellular forms
 
 
 
 
Sponge Activity-What did you learn today?
l 1. In general, how do algae and protozoans differ? (Concept 28.1)
l 2 . _____ are eukaryotic autotrophs that float near the surface of water and are the basis of the food chain. (Concept 28.1
l 3. How does Euglena obtain energy? (Concept 28.3)
l 4. A sign on the beach states, "Beach Closed. Red Tide." The organisms interfering with your use of this beach are _____. (Concept 28.4)
l 5. Groups of seaweeds can generally be distinguished on the basis of _____. (Concept 28.5)