BIO141 Unit 3 Exam

Mycology

The study of fungi

Fungi Classifications

Kingdom - Fungi

Nutritional Type - Chemoheterotroph

Multi-cellularity - All, except yeasts

Cellular arrangement - Unicellular, filamentous, fleshy

Food acquisition method - Absorptive, external digestion

Characteristic features - Sexual & asexual spores

Kingdom Fungi

• 70,000 species in 2 groups:

  • MACROSCOPIC fungi (mushrooms, puffballs, gill fungi)

  • MICROSCOPIC fungi (molds, yeast)

    • Majority are unicellular or colonial; a few have cellular specialization

Adverse Impacts of Fungi

• Mycoses, allergies, toxin production

• Destruction of crops & food storages

Beneficial Impacts of Fungi

• Decomposers of dead plants/animals

• Sources of antibiotics, alcohol, organic acids, and vitamins

• Used in making foods and in genetic studies

Fungal Characteristics

• Cell wall made of chitin (polysaccharide)

• Microscopic yeast: may be entire life cycle, may be portion of life cycle (alternating with multicellular stages)

• Chemoheterotrophs: external digestion; excrete enzymes onto food & absorb nutrients

Fungal Life History

• Saprobes:

  • Chemoheterotrophs

  • Live on dead/decaying materials

  • Bacteria + Fungi = major group of decomposers

  • Recycle nutrients back into soil

• Parasites:

  • Mycoses - fungal infection

  • Plants & animals

Diversity of Fungi

• Ex.

  • Sulfur Shelf Fungus - Laetiporus

  • Big Laughing Mushroom - Gymnopilus

  • Baker’s Yeast Cells - Saccharomyces cerevisiae

Fungal Nutrition

• Hyphae: slender filaments in a branching pattern

  • Vegetative hyphae: fungal feeding structures

  • Reproductive hyphae: may be modified for reproduction

• Mycelium: mass of hypha; grow into organic material or host

Hyphae Forms

• Septate

  • Cells grow in a chain

  • Large pores allow for movement of nucleus, organelles, and nutrients

• Coenocytic

  • No septa dividing cells

  • Multinucleated

Fungal Reproduction

• Most multicellular fungi can reproduce asexually & sexually

  • Produce spores - released in air from modified hyphae

  • Have genetically different mating types (+/-)

  • 3 genetic stages in life cycle: haploid (n), dikaryotic (n+n), and diploid (2n)

Typical Life Cycle

• Haploid Stage (n):

  • Hyphae & mycelium

  • + and - types

  • Release haploid spores

• Dikaryon Stage (n+n):

  • Haploid spores fuse

  • Nuclei remain

  • Separate

  • Often grow into hyphae & mycelium

• Diploid Stage (2n):

  • Nuclei of dikaryon fuse

  • Reduced stage

  • Undergoes meiosis and produces haploid spores

Spores

• Lightweight - easily dispersed through air or water

• Dormant stage protects spore when conditions are unfavorable

  • Germinate when conditions are favorable

• Produced in extremely large amounts

**TYPES

• Asexual reproduction: spores formed through budding or mitosis

  • Conidia (no sac); Sporangiospores (sac)

  • Produced by the millions

  • Aspergillus

• Sexual reproduction: many different types; used to classify the fungi

  • Mushrooms

Unicellular Fungi

Exist is 2 morphologies:

• Yeast: round ovoid shape; asexual reproduction

• Molds: hyphae; long filamentous fungi or molds

• Some can exist in either form (dimorphic) - characteristics of some pathogenic molds

Phylogeny of Fungi

Evolved multicellular life form separately from animals (aquatic origins?)

Classified based on form of sexual reproduction

Ex.

• Chytridiomycota

• Zygomycota

• Glomeromycota

• Ascomycota

• Basidiomycota

Chytridiomycota

Type of Fungi

• Only group w/ flagellated spores (thought to be closest to ancient fungus (aquatic protist ancestor)

• NO hyphae

• Most are aquatic (primitive)

• Some live on land but need to be covered in water to reproduce

• Most are asexual (few exceptions)

• Many are pathogens to plants & protists (not humans)

• Harlequin Frog - amphibians have a thin membrane & need to be wet (lives in warm tropical areas) → chytrids have decimated frogs & have been very pathogenic

Zygomycota

Type of Fungi

• Reproduce sexually via zygospores

• Variety of life histories

  • Saprobes (decomposers) in soil

  • Parasitic/pathogenic to insects & other fungi

• Infect/destroy food supplies such as grains & fruits & vegetables

• Ex. Rhizopus (bread mold) & commonly on fruit

Zygospores

• 3 stages: haploid, dikaryon, diploid

• Dikaryon forms zygospore

Zygospore:

• Multinucleated cell (fusion of several cells)

• As it matures, protein layers added to create a thick, protective coat

• If conditions are tough (ex. dry), it can remain dormant. for years

• In good conditions, two fuse to form diploid stage

• Mating types + & - fuse together & form zygospore (dikaryon - 2 separate unfused sets of chromosomes)

  • Once nuclei fuse, zygospore can undergo meiosis & release haploid spores

Glomeromycota

Type of Fungi

• Makes up ~1/2 fungi in soil

• Most reproduce asexually via spores that form at the tips of hyphae (chain of cells)

• Hyphae secrete enzymes that allow for them to enter plant roots (breaks down cell walls)

• Forms MYCORRHIZAE w/ 80-90% of all land plants

  • Fungi absorb more nutrients for plants

  • Plants give sugar for fungal metabolism

Mycorrhizae

• Symbiotic relationship between fungi & plant roots

• Small nodules of fungi on/in roots

• Plants supply sugar (glucose from photosynthesis)

• Fungi absorb minerals (ex. Nitrogen & Phosphorus) & pass some to plants

Ascomycota

Type of Fungi

• Diverse group

• Called “sac fungi” b/c sacs are produced in reproduction

• Only group that contains some single & multicellular organisms

  • Some can switch; some are yeasts (single-celled)

• Some are pathogens

• Some form traps (predators) to catch organisms (like microscopic worms in soil)

• Produce asci (sac that contains spores) for reproduction

• Ex. Arthrobotrys (predatory fungi)

Asci

• In ascomycetes (type of fungi)

• Sacs containing haploid reproductive spores

• Typically long and thin (spores lined one on top of another)

• Ascocarp - large number of sacs lined up together

Important Ascomycetes

• Pathogens

  • Candida albicans (in natural microbiome, but if it grows out of control it becomes pathogenic → “thrush”

• Aspergillus - alfatoxins in spores (ex. black mold) & interfere w/ body’s nerve systems

• Penicillium - antibiotics (Penicillin 1st discovered)

• Morels - not true mushrooms but ascomycetes

• Saccharomyces - yeast

Basidiomycota

Type of Fungi

• Very diverse group

• “Club fungi” - produce basidia (club-shaped) in reproduction

• Basidia hold 4 spores at a time

• Hyphae & mycelium (networks of 100s of hyphae brands)

• Many decomposers

• Some plant parasites

• Basidiocarp: above ground mushroom; along gills on inside basidiospores produced

  • Temporary fruiting body (fungus underground year-round)

Mycelium

• In ALL fungi

• Feeding structures of fungus and each strand in hyphae

Symbiotic Fungi

• Symbiotic relationship: close dependent relationship; often live on/in another organism; usually mutually beneficial

• ENDOMYCORRHIZAE:

  • Glomeromycetes & plant roots

  • Plants gain access to increased levels of minerals from soil (phosphorus & nitrogen)

  • Fungus gets protection and food source

  • As glomeromycetes grow in & hyphae grow within a cell (“Arbuscle”)

• ECTOMYCORRHIZAE:

  • Basidiomycetes & plant roots

  • Hyphae grow around roots, not inside

  • Similar benefits as endomycorrhizae

• LICHENS:

  • Fungus & photosynthetic partner

  • MYCOBIONT - fungal portion

    • 10% organism

    • Mainly basidiomycetes & ascomycetes

  • PHOTOBIONT - photosynthetic portion

    • 90% organism

    • Ex. chlorophytes (green algae) & cyanobacteria

  • Over 13,500 unique combinations discovered

  • Grow on tree bark, rocks (very dry, little soil) - secrete acids that break down into soil

  • First things to grow after volcanic eruptions

Essential Mycorrhizae

• Wild orchids - seeds germinate & seedlings survive only with mycorrhizae present

• Plants that inhabit soils poor in mineral ions, such as tropical rain forests

• Spruce, oak, pine, & some other treason temperate forests rely on mycorrhizae

• Essential for some plants living in dry habitats

Plants

• Sister taxa to chlorophyta (green algae)

• Adapted to land environments

• Photosynthetic (primary producers)

• Cellulose cell walls

• ~260,000 species in 10 phyla (groups; more diverse than fungi)

Shared traits to chlorophyta

• Cellulose cell walls

• Photosynthetic yields stored as starch

• Chlorophyll a & chlorophyll b utilized (same pigments for photosynthesis)

Closest relative/ancestor: charophyta - green algae adapted to fresh water

Plants colonized land ~450mya (1st fossilized plants occur ~450mya)

Plant Adaptations for Land

To prevent water loss:

• SPORANGIA: protect reproductive spores

• CUTICLE: waxy covering on leaves

• STOMATA: holes that open/close for gas exchange

  • Often on bottom of flat leaves

  • Close when hot temp, & open when cold

  • Stomata allow for intake of CO2gas exchange but releases water, which is why it must be able to close too

To provide support:

• LIGNIN: tough polymer that strengthens cell walls, is important in vascular tissue, and cells connect to form tube-like structures called xylem phloem

  • Provides support so that plants can grow vertically

Vascular Tissue in Plants

• XYLEM: dead at maturity; thick lignin walls; allows for one way flow of water

• PHLOEM: alive at maturity; 2-way flow; transports water & sugar (food)

Plant Shoot Systems

• Apical Meristems

  • Meristem tissue undergoes mitosis to grow

  • Undifferentiated cells

  • Can grow & specialize into any cell type (xylem, phloem, etc)

  • Vertical growth

• Leaves

  • Modified stems for photosynthesis

  • Microphyll: single vein; narrow; club mosses (ex. Lycopodiella w/ microphyll leaves)

  • Megaphyll: later adaptation; branched veins; broad surface; ferns, mosses, seed plants

  • Large modern leaves: dense collection of xylem & phloem; numerous stomata; all appear ~150mya; proliferation of flowering plants

Plant Root Systems

• Anchor into soil

• Absorb nutrients & water

• Evolution unclear → multiple origins within plants?

Plant Life Cycle

• Mitosis occurs in both haploid & diploid cells

• ALTERNATION OF GENERATION

  • Sporophyte: diploid, produces haploid spores

  • Gametophyte: haploid, produces haploid gametes (fuse to form diploid zygote & undergoes mitosis to form sporophyte)

    • Some have dominant phases & more primitive plants have a larger haploid phase

    • Trend in land plants: gametophyte decreases and sporophyte increases

Evolution of Pollen

• Pollen grains - males gametes in protective coat (prevents drying out)

• Appear ~410mya (early in fossil record - early evolution)

• Led to an adaptive radiation (plants could now live in drier habitats)

• 410-360mya - huge diversification

• One of the hardest parts of plants - most commonly fossilized in all of plant parts

Plant Diversification

• Non-vascular plants - MOSSES

  • Small, short; wet, dewy habitats; absorb nutrients/water

• Vascular plants - FERNS & RELATIVES, GYMNOSPERMS, ANGIOSPERMS

  • Support tissue; bigger

• Seedless plants - MOSSES, FERNS & RELATIVES

  • Reproduce by spores (won’t survive long)

• Seed plants - GYMNOSPERMS, ANGIOSPERMS

  • Reproduces with seeds; surrounded by protective coat & food

Bryophytes

• Non-vascular land plants

• LIVERWORTS, HORNWORTS, MOSSES

• Lack a well-developed system for conducting water

• Live in moist places - some epiphytes (plants that grow on other plants)

• Produce flagellated sperm that must swim through water

• No true roots or lignified cells (not efficient root system)

• HAVE cuticle & stomata (some species)

• Gametophyte (haploid) stage dominant

• Gametes produced in protective gametangium (sporangium)

  • Egg in archegonium and sperm in antheridia

Mosses

Phylum Bryophyta - part of Bryophytes

• Form tufts (carpets of vegetation on surfaces)

• Have stomata (guard cells; open/close)

• Gametophytes produce spores in gametangia

• Sporophytes may eventually develop chloroplasts (small photosynthetic phase), but initially depend on gametophytes for food

• May also reproduce asexually by gamma (asexual spores)

Seedless Vascular Plants

• Reproduce by spores (primitive)

• Flagellated sperm (primitive) require films of water

• Sporophyte stage is larger (new; diploid; more 50/50; diploid stage growing)

• Vascular tissue for transport (allows for vertical growth)

• Dominant plant life for ~200my in early Paleozoic (first forests)

Club Mosses & Ferns

• Relationships not clearly understood (which first?)

• 2 phyla:

  • Lycophyta (club mosses & close relatives)

  • Pterophyta (ferns, whisk ferns, & horsetails) → major group seen today (~12,000 species only)

• Rise of carboniferous forests

  • Ancient forests of seedless vascular plants (spores for reproduction)

  • Dense growth

  • First fossils of roots

  • Tree-like forms

  • Coal deposits formed from these forests

Lycophyta

• Club mosses (seedless vascular plants)

• Low-growing

• Sporophyte (diploid) dominant stage (50/50 in ferns)

• Small amounts of xylem (hollow tubes transporting water) in sporophyte

• Gametophytes (haploid) often soil symbionts w/ mycorrhizae

• Flagellated sperm must swim to fertilize the egg

Pterophyta

• Ferns (seedless vascular plants)

• Sporophyte (diploid) stage dominant (still around 50/50)

• Leaves are fronds (large complex leaves appear in fossil record)

• Multiple bundles of vascular tissue

• Waxy cuticle on top and stomata on bottom

• Fiddleheads = emerging fronds

• Stems travel underground and are called rhizomes

  • Not true root, just underground stem since it has buds just like stems, not roots

Fern Life Cycle

Haploid

• Gametophyte stage (haploid)

• Typically free-living photosynthetic multicellular stage (in moist soil)

• Heart-shaped (~1 1/2in tall) Prothallus

  • Contains archegonium (egg) and antheridia (sperm)

• Self-fertile

• Fertilization forms sporophyte (diploid stage)

Diploid

• Sporophyte (diploid) stage dominant

• Obtains nutrients from gametophyte

• Once self-sufficient gametophyte dies off, larger diploid stage

• Produce structures called sori (clusters of specialized tissue sporangia containing haploid spores (released by the millions); often underside of fronds)

• Spore released to form gametophyte

Seed Plants

• Seed

  • Contains embryonic sporophyte

  • Food source - tissue contains carbs & lipids & provides energy for early growth (endosperm) → some produce large seeds to last long, or small seeds to have many

  • Provides tough protective coat (often waterproof & w/ proteins)

• 2 groups of seed plants:

  • Gymnosperms: “naked seeds”; ex. ponderosa pine

  • Angiosperms: flowering plants; ex. orchid

    • Seeds in fruits & pollen → allow plants to live in drier habitats

• Replaced carboniferous forests of club mosses & ferns

• Dominant group; now ~95% of plants on Earth

Gymnosperms

• Seed plant

• <1,000 species

• Conifers make up majority

• Once dominant group (Mesozoic) until ~100,000yrs ago Angiosperms took over

• Contains:

  • Conifers

  • Cycads

  • Gnetophytes

  • Gingko

• Traits:

  • Seeds

  • Larger size (1st true “woody” species (layers vascular tissue - xylem & phloem); lateral meristem (tissue that allows for lateral growth (widening of stem)))

  • Pollen (waxy & waterproof container; contains 2 non-motile sperm; released in 10s millions into air)

  • Ovule (protective structure containing egg (bottom of layers of protective tissue); attached to sporophyte (diploid))

  • Fertilization by air, water NOT required

Cycads

• Gymnosperm

• Once very dominant group

• Less than 200 species

• Mostly tropical regions

• Large cone-shaped strobili (cone)

• Ex. Encaphalartos

Gingkoes

• Gymnosperm

• Males commonly planted in urban areas

• Resistant to many insects & air pollution

• Gingko biloba - only extant species

Gnetophytes

• Gymnosperm

• Several desert-adapted species

• Some w/ deep tap roots

• Some w/ 2-step fertilization (similar to angiosperms)

• Ex. Welwitschia

Conifers

• Gymnosperm

• Over 80% of all extant gymnosperms

• Spruce, cedar, pine, fir, cypress

• Needle-like leaves - arid habitats

• Mostly evergreens (don’t lose leaves)

• Separate male (pollen producing) & female cones (ovule producing)

Gymnosperm Life Cycle

Ex. Pine

• Male cone (strobilus) produces pollen (microspore)

  • Winged pollen grain is haploid & contains 2 haploid sperm (unflagellated)

• Female strobilus typically much larger

  • Scales contain ovules & ovules contain megaspores which eventually develop into female gametophytes (egg cells)

• Pollination:

  • Wind delivers pollen to female cone

  • Pollen germinates & grows pollen tube down cone toward ovule

  • Sperm travel in tube

  • Pollen germination stimulates completion of egg development (finish meiosis to produce mature egg)

  • Fertilization yields seed

Angiosperms

• Seed plants

• Flowering/fruiting plants

• Over 250,000 species

• Appear in fossil record ~200mya

• Sister clade to gymnosperms

• Very few early fossils - little known

• 3 types:

  • Magnolias (basal angiosperms; primitive form)

  • Monocots (single leaf (cotyledon) in seed)

  • Eudicots (2 cotyledons in seed; make up 90% angiosperms)

Angiosperm Adaptations

• More efficient vascular tissue (more cell types)

• Double fertilization (one sperm fertilizes egg to form diploid embryo; one sperm forms triploid endosperm to grow & form food source around embryonic plant)

• Ovary (shelters ovule; can contain one or many ovules)

• Flowers (reproduction; pollen attach to pollinators)

• Fruits (seed protection & dispersal; 1+ seeds; fleshy or hard fruits (ex. apples vs nuts))

Basal Angiosperms

• Angiosperm

• Many small groups branched w/ magnolias

• Contains:

  • Magnoliids

  • Chloranthales

  • Austrobaileyales

  • Nymphaeales

  • Amborella

Monocots

• Angiosperm

• Single cotyledon (forms single leaf to start when growing)

• Single groove in pollen grains

• 60,000+ species

• Includes grasses, orchids, tulips, palms

• Crops include: wheat, corn, rice, barley

Eudicots

• Angiosperm

• 2 cotyledons (embryonic leaves)

• 3 grooves in pollen grains

• Over 200,000 species

• Includes flowering shrubs & trees, herbs, & cacti

• Ex. beans

Flowers

• Major adaptation of angiosperms

• Many are wind pollinated

  • Flowers reduced in size (not “showy”)

  • Produce large amounts of pollen

• Anthers produce pollen

• Style/stigma deeper and sticky to catch pollen

• Ex. Oak catkins (strings each w/ ~100 tiny flowers)

Flowers - Coevolution with Animals

• Animal pollination

• Utilize animals to carry pollen

• Provide “rewards” - nectar, wax, pollen itself

• Much more efficient than wind

• Many types of pollinators (insects, bats, birds)

• Coevolution - both plant & pollinator adapt to one another

Floral Diversity

Despite tremendous diversity, all flowers have the same basic flower & fruit structure

Floral Structure

• Whorl 1 - Calyx

  • Made of individual sepals (leaf-like; often green; parts that cover bud before blooming)

• Whorl 2 - Corolla

  • Petals (“showy”)

• Whorl 3 - Stamen

  • Male reproductive parts

• Whorl 4 - Pistil

  • Female reproductive parts (1+ carpels w/ ovules)

Stamen

• Whorl 3 of flowers

• Male parts

• Filament: stalk places anther on appropriate places to release pollen

• Anther: contains pollen sacs; produce & release pollen when mature

Pistil

• Whorl 4 of flowers

• Female parts

• 1+ carpels (often fused)

• Carpel:

  • Stigma: sticky top to catch pollen (which carry sperm)

  • Style: stalk holding up stigma

  • Ovary: contains 1+ ovules (each ovule has 1+ eggs)

Flower Classification

• Complete flower: contains all 4 whorls

• Incomplete flower: missing 1+ whorls

• Perfect flower: both stamen & pistil (often don’t fertilize themselves; stamen often mature first)

• Imperfect flower: only one or the other

  • By definition also incomplete

  • Male & female flowers

  • Monoecious - male & female flowers on SAME PLANT

  • Dioecious - SEPARATE male and female PLANTS

Monocot vs Eudicot Flowers

Monocots:

• Whorls in 3’s (ex. 3 sepals, 3 petals) or multiples of 3’s

• Sepals often modified to look like petals

Eudicots:

• Whorls in 4’s or 5’s or multiples of 4 or 5

• Green sepals typically

Pollen

• Diversity in outer shell (but always waterproof, proteins, lipids, etc)

• Meiosis in anther produces haploid cells

  • These cells develop into pollen

• Pollen grains contain 2 nuclei

  • When pollen lands on stigma, tube nucleus grows pollen tube to reach ovule & other generative nucleus is used for fertilization, which divides by mitosis to create 2 sperm nuclei to cause double fertilization

Ovary in Flowers

• Contains 1+ ovules

• Layer of protection for ovules

• Meiosis produces haploid cells

  • 3 degrade & 3 rounds of mitosis w/o cytokinesis produces single cell (ovule) w/ 8 nuclei

• 2 polar nuclei in ovule form endosperm when fused with one of sperm nuclei

• Egg nucleus (1 of 3 central nuclei) - extra 2 (synergids) next to egg cell to support it

• 3 antipodal nuclei degrade

Stigma & Pollen Compatibility

• Pollen will not germinate & grow pollen tube on stigma of another species

• Chemical incompatibility - mostly proteins

• Some plants self-incompatible to prevent inbreeding

Embryonic Development

• Mitosis of egg cell begins development

• Eudicots: 2 cotyledons form

• Monocots: 1 cotyledon forms

• Endosperm grows around embryonic plant (triploid so it grows faster & provides lots of nutrients)

Fruit Development

• Simple Fruit

  • 1 carpel (or several fused) develops into fruit

  • Ex. pea fruit

• Aggregate Fruit

  • Separate carpels of one flower

  • Ex. raspberry

• Multiple Fruit

  • Many carpels of many flowers that form inflorescence

  • Ex. pineapple

• Accessory Fruit

  • Develops largely from tissues other than ovary

  • Ex. apple

Floral Adaptations

• Bat pollinators

  • Flowers open at night, white-pale petals, lots of nectar (sugar water), tube-shaped

• Hummingbirds

  • Fragrant flowers, large red petals, long tubes w/ nectar at bottom

• Moths

  • White/pale petals, open at night, fragrant, tube-shaped (small skinny flowers)

• Butterflies

  • Fragrant flowers, red & orange petals, tubes w/ nectar, open during day

• Bees

  • Yellow & orange petals, large amounts of pollen - wax, nectar too, UV patterns for bees to be guided toward rewards

• Beetles

  • Flowers imitate smells of rotting flesh, reduced petals, nectar reward