Diversity of Protists and Fungi Chapter 13 Part 2

What are protists?

Protists are eukaryotic organisms that do not fit into the kingdoms:

• Animals

• Plants

• Fungi

They are an extremely diverse group with over 100,000 known species.

Are protists prokaryotic or eukaryotic?

Protists are eukaryotes, meaning they have:

• A nucleus

• Membrane-bound organelles

• Linear chromosomes

• Complex internal organization

Are most protists unicellular or multicellular?

Most protists are unicellular.

Examples:

• Amoeba

• Euglena

• Paramecium

Some are multicellular, such as giant kelp and seaweeds.

What are examples of unicellular protists?

Common examples include:

• Amoeba

• Paramecium

• Euglena

Each consists of a single highly specialized cell capable of carrying out all life functions.

What are examples of multicellular protists?

Examples include:

• Giant kelp

• Brown algae

• Red algae

• Green algae

Some giant kelps can grow over 200 meters (650 feet) long.

Where do most protists live?

Most protists live in:

• Freshwater

• Oceans

• Wet soil

• Damp environments

Nearly all require moisture to survive.

How large can protists be?

Protists range from:

• Microscopic single cells
  to

• Giant kelp over 200 meters long.

How do protists reproduce?

Protists reproduce:

• Asexually (most common)

• S e x ually (some species)

Many species can do both depending on environmental conditions.

How do protists reproduce asexually?

Most reproduce by mitosis, producing genetically identical offspring.

How do protists reproduce sexually?

Sexual reproduction involves:

• Meiosis

• Formation of gametes (sperm and eggs)

• Fertilization

This increases genetic diversity.

What is a spore?

A spore is a haploid reproductive cell.

Spores:

• Can develop into new organisms

• Often survive harsh conditions

• May remain dormant until conditions improve

What is a cyst?

A cyst is a dormant resting stage formed during unfavorable conditions.

Functions:

• Protection

• Survival during drought or starvation

• Allows dispersal

Were protists once considered a kingdom?

Yes.

They were once classified as Kingdom Protista.

Modern DNA evidence showed they do not form one natural evolutionary group.

Why is Kingdom Protista no longer used?

Because protists are not monophyletic.

Different protists are often more closely related to:

• Animals

• Plants

• Fungi

than they are to other protists.

What does monophyletic mean?

A monophyletic group contains:

• One common ancestor

• All of its descendants

Protists do not satisfy this definition.

How is Domain Eukarya classified today?

Into six supergroups.

Protists occur in all six.

Why is DNA sequencing important for classifying protists?

Physical appearance can be misleading because of convergent evolution.

DNA sequencing provides much more accurate evolutionary relationships.

What are heterotrophic protists?

Protists that obtain food by consuming other organisms or organic matter.

Often called protozoans.

How do protozoans obtain food?

Many use phagocytosis.

They engulf food particles into food vacuoles where digestion occurs.

What is phagocytosis?

A process where a cell surrounds and engulfs food particles.

The food becomes enclosed inside a food vacuole.

What are saprobes?

Organisms that absorb nutrients from dead or decaying organic matter.

They act as decomposers.

What are photosynthetic protists?

Protists containing chloroplasts that perform photosynthesis.

Collectively called algae.

Can some protists both photosynthesize and consume food?

Yes.

Some protists are mixotrophs.

Example:

Euglena

It photosynthesizes in sunlight but feeds heterotrophically when light is unavailable.

What are the three main methods of movement in protozoans?

1. Flagella

2. Cilia

3. Pseudopods

What are flagella?

Long whip-like structures used for movement.

Example:

Euglena

What are cilia?

Numerous short hair-like structures.

They beat together to propel the organism.

Example:

Paramecium

What are pseudopods?

Temporary extensions of the cytoplasm.

Used for:

• Movement

• Capturing food

Example:

Amoeba

Are all protists free-living?

No.

Protists may be:

• Free-living

• Mutualistic

• Parasitic

What is a mutualistic protist?

A protist living with another organism where both benefit.

Give examples of mutualistic protists.

Examples include:

• Protozoans in termite intestines digest cellulose.

• Zooxanthellae living inside coral.

Why are protists important to termites?

Termites cannot digest cellulose.

Protists living in their gut produce enzymes that digest wood.

What are zooxanthellae?

Photosynthetic dinoflagellates living inside coral tissues.

They provide sugars through photosynthesis.

What do corals provide to zooxanthellae?

Corals provide:

• Protection

• Carbon dioxide

• Nutrients

The algae provide food through photosynthesis.

Why are protists ecologically important?

Protists:

• Produce oxygen

• Form the base of aquatic food webs

• Recycle nutrients

• Decompose organic matter

What is plankton?

Tiny organisms suspended in water.

Many protists are plankton.

Why is plankton important?

Plankton forms the base of most aquatic food chains.

Many fish and marine animals depend on it.

Approximately how much of Earth's photosynthesis is performed by algae?

About 25% (one-quarter) of global photosynthesis.

Why are algae important producers?

They convert sunlight into chemical energy.

They also produce enormous amounts of oxygen.

What role do saprobic protists play?

They decompose dead organic matter.

This recycles nutrients back into ecosystems.

Can protists be aerobic or anaerobic?

Yes.

Different protists have evolved to survive under both oxygen-rich and oxygen-poor conditions.

Protists are

eukaryotes

Most are unicellular,

but some (kelp) are multicellular.

Reproduction:

• Mitosis

• Meiosis

• Spores

• Cysts

Most live in

aquatic or moist environments.

Nutrition:

• Heterotrophs (protozoans)

• Photosynthetic (algae)

• Mixotrophs (Euglena)

Nutrition:

• Heterotrophs (protozoans)

• Photosynthetic (algae)

• Mixotrophs (Euglena)

Movement:

• Flagella

• Cilia

• Pseudopods

Important ecological roles:

• Produce oxygen

• Base of aquatic food webs

• Decomposers

• Mutualists (corals, termites)

Why are protists economically important?

Protists provide many useful products, including:

• Medicines

• Food additives

• Plastics

• Industrial chemicals

They also play major roles in agriculture and ecosystems.

How are protists used in medicine?

Compounds from certain protists are used to help treat:

• High blood pressure

• Digestive disorders

• Ulcers

• Arthritis

Scientists continue to study protists for new medicines.

How are red algae used in food production?

Extracts from red algae (such as agar and carrageenan) are used as thickening and stabilizing agents in foods like:

• Ice cream

• Puddings

• Jellies

How are algae used in manufacturing?

Chemicals extracted from algae are used to produce:

• Plastics

• Cosmetics

• Pharmaceuticals

• Food additives

Why are protists important to termites and cockroaches?

Protists living in their digestive systems break down cellulose in wood.

Without these protists, termites could not digest wood.

Can protists cause disease?

Yes.

Many parasitic protists infect humans, animals, and plants.

Some cause life-threatening illnesses.

What causes malaria?

Malaria is caused by Plasmodium species, especially Plasmodium falciparum.

It is transmitted by female Anopheles mosquitoes.

Why is Plasmodium falciparum dangerous?

It causes the most severe form of malaria.

The parasite infects red blood cells, leading to:

• Fever

• Chills

• Anemia

• Organ failure

• Death if untreated

What causes African sleeping sickness?

A protist called Trypanosoma.

It is spread by the tsetse fly.

What causes Chagas disease?

Another species of Trypanosoma.

It is transmitted by the "kissing bug."

What disease is caused by Trichomonas vaginalis?

A sexually transmitted infection called trichomoniasis.

“brain-eating amoeba”

Primary amoebic meningoencephalitis

Which major plant diseases are caused by protists?

• Downy mildew

• Powdery mildew (historically grouped with protist-like organisms in some courses)

• Potato late blight

These diseases can destroy crops and cause severe economic losses.

What caused the collapse of the French wine industry in the 1800s?

Downy mildew infected grape vines.

• Disease spread rapidly.

• Destroyed vineyards.

• Caused major economic losses for France.

What caused the Irish Potato Famine?

Potato late blight

• Caused by Phytophthora infestans

• Destroyed potato crops

• Led to famine during the 1840s

• Over one million deaths and massive emigration from Ireland

Which protist causes potato late blight?

Phytophthora infestans

Effects:

• Black lesions on leaves

• Rotting potatoes

• Crop failure

Which protist infects grape vines?

Plasmopara viticola

Causes:

• Downy mildew

• Yellow spots on leaves

• Reduced grape production

Which protist causes malaria?

Plasmodium falciparum

Characteristics:

• Infects red blood cells

• Transmitted by female Anopheles mosquitoes

• Causes severe malaria

Which protist causes African sleeping sickness?

Trypanosoma

Characteristics:

• Blood parasite

• Spread by tsetse flies

• Causes fever, fatigue, and neurological symptoms

What are fungi?

Fungi are:

• Eukaryotic organisms

• Heterotrophs

• Non-photosynthetic

• Mostly multicellular

• Have chitin cell walls

• Reproduce using spores

Why are fungi no longer classified as plants?

Because fungi:

• Do not photosynthesize

• Are heterotrophs

• Store glycogen (not starch)

• Have chitin cell walls instead of cellulose

• Are genetically more closely related to animals

What is a heterotroph?

An organism that obtains nutrients from other organisms instead of producing its own food.

Fungi are heterotrophs.

How do fungi obtain nutrients?

1. Release digestive enzymes outside the body.

2. Digest food externally.

3. Absorb dissolved nutrients.

This is called extracellular digestion.

What is a saprophyte?

A decomposer that feeds on dead organic matter.

Importance:

• Recycles nutrients

• Breaks down dead plants and animals

• Returns nutrients to ecosystems

What are the major nutritional roles of fungi?

1. Saprophytes (decomposers)

2. Parasites (harm hosts)

3. Mutualists (benefit both organisms)

What is chitin?

A tough carbohydrate found in:

• Fungal cell walls

• Arthropod exoskeletons

Provides strength and protection.

What energy storage molecule do fungi use?

Glycogen

Same storage molecule used by animals.

What is a hypha?

A long, threadlike fungal filament.

Functions:

• Absorbs nutrients

• Grows rapidly

• Forms the fungal body

What is a mycelium?

A network (mass) of hyphae.

Functions:

• Main feeding structure

• Absorbs water

• Absorbs nutrients

• Anchors fungus

Why are hyphae efficient at absorbing nutrients

Because they:

• Have enormous surface area

• Grow rapidly

• Penetrate food sources

What are septa?

Cross-walls that divide hyphae into separate cells.

Functions:

• Separate cells

• Allow controlled movement of materials

What are coenocytic hyphae?

Hyphae without septa.

Characteristics:

• One continuous cytoplasm

• Many nuclei

• Large multinucleated cells

Example:
Bread mold

What is the vegetative body of a fungus?

The thallus

May be:

• Unicellular

• Multicellular

• Dimorphic

What does dimorphic mean?

Alternates between:

• Unicellular form

• Multicellular form

Depending on environmental conditions.

How do fungi reproduce?

Both:

• Sexually

• Asexually

Main reproductive cells:
Spores

Why are spores important?

Spores:

• Spread fungi

• Survive harsh environments

• Grow into new fungi

Approximately how many fungal species exist?

• About 100,000 described

• Estimated 1.5 million total

What are chytrids?

Primitive fungi that:

• Live in water and soil

• Have flagellated spores

• Include decomposers, parasites, and mutualists

Why are chytrids unique?

They are the only fungi with flagellated spores.

Most other fungi have non-motile spores.

Which disease has caused worldwide amphibian declines?

Chytridiomycosis

Caused by:
Batrachochytrium dendrobatidis

Characteristics of zygospore fungi?

• Food molds

• Animal parasites

• Commensals

• Form resistant zygospores during sexual reproduction

What percentage of fungi are sac fungi?

Approximately 75%

Examples of Ascomycota

• Yeasts

• Morels

• Cup fungi

• Penicillium

• Plant pathogens

• Lichens

What are asci?

Sac-like reproductive structures.

Function:
Produce spores by meiosis.

What are conidia?

Asexual spores formed in chains at hyphal tips.

Importance of yeast

Used in:

• Bread making

• Beer

• Wine

• Fermentation

Importance of Penicillium

Produces:

• Penicillin

• Blue cheese

Examples of Basidiomycota

• Mushrooms

• Puffballs

• Shelf fungi

What are basidia?

Club-shaped reproductive structures that produce spores by meiosis.

What is the fruiting body of Basidiomycota called?

Basidiocarp

Example:
Mushroom

What is a mycosis?

A fungal disease affecting plants or animals.

Examples of plant fungal diseases

• Powdery mildew

• Rust

• Fruit mold

• Food spoilage

• Crop rot