BIOL172 Exam 1 Guide 1: Protists and Fungi

What defines a protist?

Eukaryotic organism that mainly unicellular microscopic but can be multicellular, colonial, and macroscopic

Animal-like, plant-like, and fungus-like (but are missing key characteristics)

Why are protists considered a paraphyletic group?

Protists as a taxonomic grouping contains some but not all the descendants of a common ancestor (do not contain plants, animals, and fungi)

What are the main modes of locomotion used by protists? Explain each one.

Cilia

- Short hair like projections

Flagellum

- long whip like or rotating appendage

Pseudopodia

- lobe like extensions of the cytoplasm, also used for phagocytosis

Differentiate asexual from sexual reproduction in protists.

Asexual Reproduction

- One parents producing identical offspring

- Mitosis

- Binary fission

-Budding

Sexual Reproduction

- Two parents exchanging genetic material to produce offspring

- Meiosis

- Conjugation (horizontal gene transfer, two cells temporarily join to exchange material through a sex pilus)

- Syngamy (gamete fusion to form a zygote)

Protists can switch between the two when there is low availability of nutrients, environmental changes, and resistant cysts (T, pH, desiccation)

Define accessory pigments and list the groups of protists that exhibit them.

Accessory Pigments:

- Light absorbing compounds (which complement chlorophyll a) that broaden the wavelengths that can be used for photosynthesis

Plastids:

- Specialized double membrane bound organelles crucial for photosynthesis, pigment synthesis, and nutrient storage

Red algae

- phycoerythrin (lacking in parasitic species)

Brown algae

- fucoxanthin

- xanthophyll

Diatomes

- fucoxanthin

Dinoflagellates

- peridinin

Golden algae

- carotenoid

- fucoxanthin

List the six major eukaryotic supergroups and indicate which include only protists.

Archaeplastida

- contain land plants

Amoebozoa

Opisthokonta

- contain fungi and animals

Rhizaria

Chromalveolata

Excavata

Differentiate heterotrophic, autotrophic, and mixotrophic organisms

Heterotrophic

- Derives nutritional requirements from complex organic substances, cannot synthesize own food

Autotrophic

- Chloroplasts via red algae secondary endosymbiosis

- Produce own food using inorganic substances, sunlight (photoautotrophs), or chemical energy (chemoautotrophs)

Mixotrophic

- Use a combination of heterotrophic and autotrophic traits

Describe the main characteristics of Excavata and give one example of a protist from this group.

Not monophyletic

Excavated groove on the side of the cell body

Plastids absent except for Euglenids / Euglenozoans

Most are found in anaerobic environments

Reduced mitochondria into mitosomes (lack DNA and do not produce ATP, usually found in unicellular parasitic eukaryotes) and hydrogenosomes (lack DNA but produce ATP) due to anaerobic environment

Diplomands

- Mitosomes

- Mostly parasites

- Multiple flagella (4)

Parabasalids

- Hydrogenosomes

- Parabasal apparatus (Golgi complex associated with cytoskeletal fibres)

- STD: females more vulnerable to HIV and cervical cancer, pregnancy complications

- Colonize rumen (cellulose digestion, unusual in eukaryotes)

Euglenozoans

- Pyrenoid: protein based mass, sugars into para-starch

- Flagella with spiral or crystalline rod inside

- Aquatic

- Heterotrophic, autotrophic, mixotrophic, pathogenic parasites

What is the significance of Chromalveolata, and what are the two main subgroups it includes?

Partially photoautotrophic via secondary endocytobiosis with Rhodobionata

Alveolates and Stramenopiles (+ Rhizaria = SAR, monophyletic)

Alveolates

- Membrane bound sacs under plasma membrane (alveoli)

- Dinoflagellates

- Apicomplexans

- Ciliates

Stramenopiles

- Hairy flagellum (some species with additional hairless flagellum)

- Single cell and multi cell

- Chloroplasts from Red algae (Rhodobionta)

- Photosynthetic marine algae and heterotrophic protists

- Diatomes

- Golden Algae

- Brown Algae

Why are Dinoflagellates, Apicomplexans, and Ciliates grouped into the Alveolates clade? Define the main characteristics of these three subgroups.

They share the common evolutionary trait of alveoli: membrane bound sacs under plasma membrane

Dinoflagellets

- Photosynthetic, heterotrophic, or mixotrophic

- Unicellular, rarely filamentous (thread like)

- Flagella absent or in 2 groups: 1 longitudinal and 1 transversal for spinning motion

- peridinin as accessory pigment

Apicomplexans

- Apical complex: organelles specialized for penetrating the host cells and tissues (highly modified secondary chloroplasts)

- Parasites of animals

- Sporozoites: tiny infectious cells

- Complex life cycles with 2 hosts

- Malaria

Ciliates

- Cilia for locomotion and nutrition

- Most are predators

- Cilia might cover entire cell or clustered in rows or tufts

- Contractile vacuole, cell mouth, anal pore

- Food engulfed into food vacuoles by phagocytosis, waste released with specialized region of plasma membrane that functions as an anal pore

- Contractile vacuole accumulate excess water and expel it through plasma membrane (bladder and tubular networks)

What is the main trait that groups Stramenopiles within this clade?

1 hairy flagellum (some species have another hairless flagellum) or no flagellum

Chloroplasts derived from red algae (Rhodobionta)

Single celled and multi celled organisms

Diatomes

- Frustule formed by pair of valves (cell wall with two overlapping halves)

- Fucoxanthin

- Primary food source for aquatic animals

Golden Algae

- Cell walls with cellulose fibrils with minerals or absent

- Interlocking scales with silica

- Fucoxanthin

Brown Algae

- Benthic: beaches of coldest regions of the clobe

- Alginate: used as an emulsifier in products

- Fucoxanthin and Xanthophyll

- germ cells with 2 flagella

Why are Oomycetes not considered true fungi?

They have a cellulosic cell wall without chitin

How do Rhizaria differ from other protists in terms of structure and ecology?

Threadlike, needle like, or root like pseudopodia species

Elaborate shells (or tests) of calcium carbonate, silicon, or strontium salts (armor-like or porous skeletons, protective coverings)

Important Carbon and Nitrogen cycles

- responsible for the carbon pump in the ocean (away from the atmosphere)

Explain the role of Archaeplastida in the evolution of photosynthetic organisms. Identify examples of protists within this group.

Unicellular, multicellular, and colonial forms

Alternation of generations

Primary Endosymbiosis: developed plastids

Secondary Endosymbiosis: origin of photosynthesis / chloroplasts

Rhodophytes (Red algae)

- lack flagella

- phycoerythrins (lacking in parasitic spp.)

- CH storange in cytoplasm

Green Algae (Chlorophtyes and Charophytes)

- Chlorophytes: true green algae, two flagella, spherical matrix

- Charophytes: spiral shaped chloroplasts, conjugation

How do Amoebozoa move and capture food? Provide an example. Provide examples of protists in this group and discuss their ecological importance.

Pseudopodia (substrate anchorage and locomotion)

Free living and parastic species

Single cells, large multinucleated cells, multicellular phases

Gymnamoebae

- lobose amoeba (naked and shelled)

- ectoplasm: devoid of organelles, large amount of actin, leads pseudopods

Entamoebas

- symbiotic parasites

- the flux outbreak

- humans host around 6 species

- pathogenic: E. histolytica (amoebic dysentery)

Slime Molds

- fungi like (no chitin)

- engulf food instead of externally digest it

- multinucleate mass

What are Opisthokonts, and which groups are included besides protists?

Fungi, animals, and closely related protists

Choanoflagelletes:

- Closely related to animals (resemble the sponges common ancestors)

- Single posterior flagellum

- Unicellular and colonial forms

- Collar / Microvili: contractile structure (filter feeder, collects food particles as flagella moves)

Describe one ecological role of protists in aquatic ecosystems

Primary production: oxygen

- Carbon, Nitrogen, and Silicon cycles

Food source

Decomposers

Symbiotic relationships

Pathogens and parasites

Environmental indicators (sensitivity to water quality)

Name one parasitic protist mentioned in the chapter and the disease it causes

Apicomplexans: malaria through mosquitos

Parabasalids: STD: increase cervical cancer, HIV, and pregnancy complications in women

How do protists reproduce, and what are the differences between asexual and sexual reproduction?

Asexual: binary fission and budding

- clones, genetically identical offspring

Sexual: meiosis and syngamy or conjugation (increases genetic variation, during environmental stress)

- alternation of generations (diploid and haploid phase)

- genetically diverse offspring

Explain how protists contribute to global nutrient cycles.

Carbon cycle: oxygen production

Nitrogen and Phosphorous cycles (predators of bacteria that store nutrients)

Bacterial Redistribution: transport bacteria

Symbiotic Relationships: parabasalids in rumen (cellulose digestion), dinoflagellates in coral tissues (energy through photosynthesis, recycle nutrients)

Compare the movement and feeding mechanisms of protists in the Excavata and Amoebozoa supergroups

Excavata

- flagella

- excavated groove for feeding (food particles are trapped then phagocytosis)

Amoebozoa

- pseudopods for locomotion and phagocytosis

- pushes cytoplasm / endoplasm forward

Which protist supergroup includes the ancestors of land plants?

Archaeplastida

- Red algae, Chlorophytes and Charophytes (green algae), Land plants

Which is the same difference between Amoebozoa and Rhizaria?

Amoebozoa

- lobose (lobed) pseudopodia (substrate anchorage and locomotion)

Rhizaria

- thread like, needle like, or root like pseudopodia

- tests (protective shells)

What are the defining characteristics of fungi?

Eukaryotes

Achlorophyllates (lack chlorophyll)

Heterotrophs

Spore producers

Absorptive nutrition: exoenzymes (release of digestive enzymes into external environment), absorb smaller molecules (requiring water for transport)

Asexual and sexual reproduction

Hyphae (filamentous and branched somatic structures that absorb nutrients) with septa or without

Chitin (non cellulosic!)

Most are sessile

Avascular

No specialized differentiation of organs (leaf, root, stem)

Little or no division of labour between somatic parts

Glycogen: main reserve carbohydrate (vs starch in plants)

Generalists and obligate parasites

What is the structure of a typical fungal body?

Hyphae --> mycelium

Chitin

Possibly septa

Fruiting bodies

Compare coenocytic to septate hyphae. In which fungal phyla can we find septate hyphae?

Coenocytic: no septa

Septate: have septa (walls that divide the hyphae into individual cells)

- allow for cytoplasmic streaming (nutrition circulation) and organelle movement while providing structural support

Phyla:

Ascomycota

Basidiomycota

What is the main compound in fungal cell walls?

Chitin

What is the main reserve carbohydrate in fungi?

Glycogen

How do fungi obtain nutrients?

Through secreting chemicals that break down food in their environment, then absorb the broken down nutrients

What are the primary modes of reproduction in fungi?

Asexual

- no karyogamy (fusion of nuclei) and meiosis

- budding, asexual spore formation, fragmentation

Sexual

- plasmogamy, karyogamy, meiosis to produce haploid spores

- conjugation

Describe the general steps and structures in a fungal life cycle.

Asexual:

asexual spores: Spores --> mycelium --> sporangia that produce genetically identical haploid spores

budding: bud develops off parent (growth)

fragmentation: parent breaks down into fragments that all turn into identical offspring

Sexual:

sexual spores: Spores released through fruiting body --> germination --> mycelium --> plasmogomy --> dikaryotic hyphae --> karyogamy --> diploid zygote --> meiosis --> spores

conjugation (Zygomycota): + and - mating type hyphae connect to form gametangia that produces zygosporangium

Define plasmogamy and karyogamy.

Plasmogomy: fusion of cytoplasm

Karyogamy: fusion of nuclei (nuclear fusion)

How are fungi classified?

Structure and method of reproduction

Septate and Coenocytic hyphae

What are the key features of Chytridiomycota?

Basal Eumycota (true fungi)

Chitin (some chitin + cellulose)

Coenocytic

Mobile cells (zoospores and gametes)

Most are unicellular

Some have rhizoids

Some are parasitic

Death of frogs: deformation in the mouths of amphibians

What distinguishes Zygomycota from other fungal phyla?

Parasites of plants, insects, animals

Pathogens

Symbionts with plants: endomycorrhizae

Zygospore (sexual reproduction if poor environmental conditions)

- thick walled spore for resistance

- formed within a zygosporangium

Coenocytic

Describe the Ascomycota phylum (including sexual and main asexual spores).

Molds that spoil food

Dark fruit rot

Pharmaceutical and food industry

Penicillin, some yeasts, edible truffles, fine cheeses

Perforated septa

Asexual reproduction: conidia that forms asexual spores

Sexual reproduction: asci (sacs where ascospores form -n)

Types of ascomas (complex structure formed by intertwined hyphae, site of asci formation): apothecium, perithecium, cleistothecium

Antheridium (male reproductive structure), ascogonium (female reproductive structure), trichogyne (branching of the ascigonium, passage of male nuclei through this structure followed by plasmogomy)

Sexual reproduction: + and - mating type --> ascogonium and antheridium connected by trichogyne --> developed ascocarp with dikaryotic hyphae --> ascus diploid --> meiosis & mitosis to form ascospores that are distributed --> mycelia

Form mycorrhizal associations (mainly ecto)

Mycangial (parasitic or mutualistic relationship): exoskeleton of beetles

What is unique about Glomeromycota?

Form arbuscular (sites of nutrient transfer between the fungus and the host plant) endomycorrhizae (most common, obligate: cannot survive without)

Coenocytic hyphae that form gigaspores: asexual cycle only

What role do fungi play in ecosystems?

Decomposers

Production of enzymes, vitamins, lactase, lactic acid, gibberellin phytohormones

Explain the mutualistic relationship between fungi and plants.

Ectomycorrhizae:

- fungus surrounds the plant root, does not go inside the plant root

Endomycorrhizae:

- fungus penetrates cell wall of plant root

Fungus gives water and nutrients to plant, plant provides carbohydrates / food

How do fungi contribute to nutrient cycling?

Decompose organic matter, recycling nutrients back into ecosystem

What is the significance of lichens?

Lichen: symbiotic fungi + cyanobacteria or algae, fungi (mycobiont) provides structure to the photobiont, the photobiont provides food to the fungus

Environmental indicators: sensitive to air pollution

Food source for animals

Break down rocks with acids, soil crusts that reduce erosion and retain moisture in dry environments

How do fungi impact agriculture?

Teliomycetes: basidiospores mass produced (coals and rusts)

Rusts and coals produce teliospores (resistant spores)

Pandemic level yield losses in essential crops like wheat, legumes, and various cereals

Plant pathogens: aiborne rusts that spread rapidly

Decrease productivity and quality of product

Causes plant diseases

Sexual and asexual

What are the uses of fungi in food production?

Cheese, yeast, bread, alcohol, wine, beer

What pharmaceutical applications do fungi have?

Antibiotics (penicillin)

Immunosuppressants for transplants

Anti-tumoral agent

Compare a) isogametangia to heterogametangia, b) homothallic to heterothallic fungi

Isogametangia:

Gametangia are morphologically identical: + and - mating types, no male or female structures

Heterogametangia:

Gametangia are different in structure: antheridium and oogonium or ascogonium

Define saprobes.

derive nutrients from dead, decaying matter

What is a parasitic fungus?

Derive nutrients from living organisms while harming them

Explain the difference between facultative and obligate parasitic fungi.

Facultative:

Do not depend as host, can live independently as saprobes

Obligate:

Require a living host to complete life cycle

What are mutualistic fungi?

Mutually beneficial relationship

Absorb sugars from plant, give water and nutrition to plant

Describe the main categories of asexual spores in Fungi. Which one is the most common in Ascomycota?

Conidia (conidiospores)

Sporangiospores: formed by sporangium, zygomycota

Arthrospores: fragmentation of hyphae (ascomycota, zygomycota, basidiomycota)

Chlamydospores: thickwalled, resistant spores (ascomycota, basidiomycota, glomeromycota)

Blastospores: budding, yeasts

In what fungi groups can we find: a) edible and poisonous mushrooms, b) bread mold, c) arbuscular mycorrhizae, d) flagellate cells, and fungal species economically important to antibiotic (penicillin) and food (truffles, morels, cheese, wine, beer) production?

a. basidiomycota

b. zygomycota

c. glomeromycota (mainly)

d. chytridomycota