Protists and Fungi

Where do Protists and Fungi belong?

tolweb.org 1/28/13

What is a Protist?• Any eukaryotic organism that

is not a plant, an animal, a fungus or a prokaryote

• Eukaryotes that are not members of the kingdoms Plantae, Animalia, or Fungi

• Most are unicellular

Evolution of Protists• Kingdom Protista “the very first”

• The first eukaryotic organisms:1.5 bya

• May have evolved from the symbiosis of several cells

• Diverse! Scientists think that there should be several kingdoms

Classification of Protists• DNA evidence that protists evolved

independently from archaebacteria

• Because the new classification is not perfected, we will break them down into the traditional groups

• These categories are an artificial way to organize diverse groups of organisms

ProtistsThe “Junk Drawer” of the Kingdoms

• Animal-like

• Plant-like

• Fungus-like

Animal-like Protists (Protozoans)

• “First animals:” protozoa

• Heterotrophs distinguished from each other by way of movement

• Flagella– Zooflagellates

• Pseudopods– Amoeba– Foraminifera

• Cilia– Paramecium

Sporozoans• Do not move on their own

• Parasitic

– Infect:

• worms, fish, birds, humans, etc.

– Cause:

• Malaria

• African Sleeping Sickness

• Most have complex life cycles involving more than one host

Plant-like Protists: Unicellular Algae• Accessory pigments: many algae

have compounds that absorb light at different wavelengths than chlorophyll

• Chlorophyll and accessory pigments allow algae to harvest and use the energy from sunlight

Plant-like Protists: Unicellular Algae

• Euglenophyte– Euglena

• Dinoflagellates

• Diatoms

Aside: What are Plankton?• Any drifting organisms that

inhabit the pelagic zone of oceans, seas, or bodies of fresh water.

• That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification. They provide a crucial source of food to larger, more familiar aquatic organisms such as fish and cetacea

• Protists are Plankton…not all Plankton are Protists!!!

• From the Greek planktos: “to drift or wander”

• Phytoplankton

– Small, photosynthetic organisms found near the surface of the ocean

– Nearly ½ of photosynthesis on Earth is carried out by phytoplankton

• Zooplankton

– Holoplankton

– Meroplankton

Symbiotic Algae• Many types of coral contain intercellular

dinoflagellates

• Dinoflagellates allow the coral animals to use the food products of photosynthesis

• Dinoflagellates can feed on the waste products of coral animals and can use the coral as a home

Algal Blooms• Many protists absorb

organic material and use it for food

• Grow rapidly in regions where sewage is discharged

• Recycle the sewage and other waste materials

• Blooms: When the amount of waste is excessive, populations grow in enormous masses

• The algal blooms deplete the water of nutrients, and the cells die in great numbers

• The decomposition of these dead algae can rob the water of its oxygen, choking resident fish and invertebrate life

Algal Blooms• Great blooms of the

dinoflagellates Gonyaulax and Gymnodinium have occurred in recent years on the east coast of the USA

• “Red Tides”: these species produce a potentially dangerous toxin

• Filter-feeding shell-fish such as clams can trap Gonyaulax and Gymnodinium for food and become filled with the toxin

• Eating shellfish infected with red tide can lead to serious illness, paralysis, and even death

Plant-like Protists: Multicellular Red Algae

• Phylum Rhodophyta, meaning “red plants”

• Able to live at great depths due to their efficiency in harvesting light energy

• Found in marine waters from the polar regions to the tropics

• Can grow in depths up to 260 m

• Most are multicellular, having complex life-cycles

• Lack flagella and centrioles

Plant-like Protists: Multicellular Brown Algae

• Phylum Phaeophyta, meaning “dusky plants”

• Largest and most complex of the algae

• Multicellular, mainly marine algae

• Found in cool, shallow coastal waters of temperate or arctic areas

• Giant kelp: the largest known brown alga

• Can grow more than 60 meters in length

• Sargassum: another huge brown alga that floats in large mats near Bermuda, in “The Sargasso Sea”

Plant-like Protists: Multicellular Brown Algae

• Fucus: a common brown alga found along the rocky coast of the eastern USA

• Each Fucus plant has a holdfast, a structure that attaches the alga to the bottom

• Bladders: gas filled swellings that float and keep the algae upright in the water

Plant-like Protists: Multicellular Green Algae

• Phylum Chlorophyta, meaning “green plants”

• Scientists hypothesize that the ancestors of modern land plants looked a lot like certain species of living green algae

• Found in fresh and salt water, and even in moist areas on land

• Many live as single cells, others form colonies

Human Uses of Algae• Algae are a major food source

for life in the oceans

• Many species of algae are rich in vitamin C and iron

• Chemicals in algae are used to treat:

– Stomach ulcers

– High blood pressure

– Arthritis, etc.

• Algae used in food production:

– Dried Porphyra-used to warp sushi

– Ice-cream

– Salad dressing

– Pudding

– Candy bar

– Pancake syrup

– Eggnog

Human Uses of Algae• Algae use in industry:

– Plastics– Waxes– Transistors– Deodorants– Paints– Lubricants– Artificial wood

• Scientific laboratories:– Agar: thickens nutrient

mixtures used to grow bacteria and other microorganisms

Fungus-like Protists• Heterotrophs that absorb nutrients from dead or decaying

organic matter

• Unlike most true fungi, fungus-like protists have centrioles

• They lack the chitin cell walls of true fungi

• Cellular slime molds

• Acellular slime molds

• Water molds

Slime Molds• Found in places that are damp and rich

in organic matter (forest or backyard compost pile)

• Play key roles in recycling organic matter

– Cellular slime molds

– Acellular slime molds

Cellular Slime Molds• Spend most of their lives as free-

living cells

• Not easily distinguishable from soil amoebas

• Reproduce rapidly in nutrient-rich soils

Acellular Slime Molds

• Also begin life as amoeba-like cells

• Cells fuse to produce structures with many nuclei

Water Molds• Thrive on dead or decaying

organic matter in water

• Are plant parasites on land

• Not true fungi

• Hyphae: thin filaments produced by water molds

• Have both sexual and asexual phases in the life cycle

Ecology of Fungus-like Protists• Important as recyclers of organic

material

• Help things rot

• Some can harm living things– Cause plant diseases–Mildews and blights of grapes and

tomatoes

Water Molds and the Potato Famine• ~ 40 million Americans can trace some part of

their ancestry to Ireland

• Potatoes – Native to South America– Introduced to Europe by Spanish explorers– By the 1840s major food crop of Ireland

• Protist: Phytophthora infestans– An oomycete that produces airborne spores that

destroy all parts of the potato plant– Reduces the potato to a spongy sac of spores and

dust

Water Molds and the Potato Famine

• Summer, 1845: unusually wet and cold

• 60% of the Irish potato crop was destroyed

• > 1 million people starved

• 1.5 million people USA

What Are Fungi?

• Eukaryotes

• Heterotrophs

• Chitin: complex carbohydrate found in the cell wall

• Also found in the external skeletons of insects

What Are Fungi?

• External digestion and reabsorption

• Many absorb nutrients from decaying matter in the soil

• Others are parasites

Structure and Function of Fungi• Multicellular

• Exception: yeasts are unicellular

• Hyphae: tiny filaments that make up fungi

• Mycelium: many hyphae tangled together that make up the bodies of multicellular fungi

• Suited to absorb food

Structure and Function of Fungi• Fruiting Body:

Reproductive structure (the mushroom!)

• Develops from an underground mycelium

• Clusters of mushrooms are often part of the same mycelium… they are a part of the same organism

Structure and Function of Fungi

• Some mycelia can live for several years

• “Fairy Rings”

Asexual Reproduction• Cells or hyphae break off from

a fungus

• Begin to grow on their own

• Sporangia: structures in ferns and some fungi that contain spores

• Sporangiophores: specialized hyphae where sporangia are found

Sexual Reproduction

• Involves two different mating types

• Gametes are not called male and female

• + and -

Reproduction in Fungi

• Gametangium: gamete-forming structure

• Produced when the hyphae of opposing mating types of fungi meet

• A diploid nucleus (zygote), is formed meiosis occurs produces haploid cells

How Fungi Spread• Fungal spores are found in almost every

environment

• Dry, almost weightless spores that scatter in the wind

• Some fungi lure animals to disperse the spores

• Stinkhorns smell like rotting meat, which attracts flies

Classification of Fungi

• Over 100,000 species

• Classified according to:

–Structure

–Method of reproduction

Fungi• Primitive fungi

• Club fungi – Basidiomycota

• Bread mold – Zygomycota

• Sac fungi – Ascomycota

The Club Fungi (mushrooms)

• Phylum Basidiomycota

• Named from a specialized reproductive structure that resembles a club

• Basidium: spore-bearing structure

• Found on the gills that grow on the underside of mushroom caps

Life Cycle of Club Fungi

• The most elaborate life cycle of all the fungi

• In a suitable environment the spore-producing fruiting bodies push above ground as mushrooms

Life Cycle of Club Fungi

• Fruiting bodies expand at astonishing speed, sometimes producing fully developed mushrooms overnight

• Cells enlarge, not divide

• When the mushroom cap opens there are gills on the underside

Diversity of Club Fungi• In addition to mushrooms,

basidiomycetes include shelf fungi, near decaying trees

• Other examples of basidiomycetes– Puffballs, earthstars, jelly fungi and

plant parasites known as rusts

The Common Molds

• Phylum Zygomycota • Familiar molds that

grow on meat, cheese, and bread

• Zygospore: resting spore that contains zygotes formed during the sexual phase of a mold’s life cycle; may remain dormant for months

Structure and Function of Molds• Rhizoids: a rootlike

hypha that penetrates the surface of an object

• Stolons: a stemlike hypha that runs along the surface of an object

• Example: black bread mold, Rhizopus stolonifer

Life Cycle of Bread Molds

The Sac Fungi• Phylum Ascomycota

• Ascus: reproductive structure that contains spores

• More than 30,000 species; the largest phylum of the kingdom Fungi

• Size variation– yeast: microscopic – cup fungi: seen with

the naked eye

ReproductionAsexual

• Tiny spores called conidia are formed at the tips of specialized hyphae called conidiophores

• Conidia that land in a good environment grow into haploid mycelium

Sexual• Haploid hyphae of two

different mating types grow close together

• A diploid zygote forms and divides by meiosis into haploid ascospores

Yeasts• Unicellular fungi

• Form asci with ascospores during the sexual phase of their life cycle

• The ascospores become active in a moist environment

Edible and Inedible Mushrooms• Many mushrooms are considered

delicacies

• When properly cooked and prepared, domestic mushrooms are tasty and nutritious

• Wild mushrooms: some are edible, many are poisonous

• Don’t eat wild mushrooms!

Ecology of Fungi: Heterotrophs

• Saprobes: organisms that obtain food from decaying organic matter

• Parasites

• Symbionts: live in close and mutually beneficial association with other species

• Capturing live animals

Fungi as Decomposers• Fungi are found in every ecosystem,

where they recycle nutrients by breaking down the bodies and wastes of other nutrients

• Release digestive enzymes that break down leaves, fruit and other organic matter

Fungi as Parasites• Parasitic fungi cause serious plant and

animal diseases

• Plant Diseases

– A few fungi cause diseases in humans

– Corn smut destroys corn kernels

– Wheat rust affects wheat fields like wildfire

Fungi as Parasites• Human Diseases

– One deuteromycete can infect the areas between the toes (athlete’s foot)

– Yeast infections

Fungi as Parasites• Other Animal Diseases

– Genus Cordyceps

– Fungus infects grasshoppers in rainforests in Costa Rica

– Microscopic spores become lodged in the grasshopper, where they germinate and produce enzymes that slowly penetrate the insect’s tough external skeleton

Symbiotic Relationships• Some fungi form symbiotic relationships in

which both partners benefit

• Two such mutualistic associations are essential to many ecosystems

– lichens

– mycorrhizae

Lichen• Symbiotic association between a fungus and a photosynthetic

organism (algae)

• Usually ascomycetes and green alga or cyanobacteria

• Resistant to drought and cold

• Can grow in places where few can survive

Lichen Joke• There was a

fungi (fun guy) and algal (a gal) and they took a lichen (liking) to each other.

Mycorrhizae

• Symbiotic association of plant roots and fungi

• The hyphae of fungi aid plants in absorbing water and minerals

• The plants provide the fungi with the products of photosynthesis