KEY CONCEPT Kingdom Protista is the most diverse...

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19.1 Diversity of Protists

KEY CONCEPT

Kingdom Protista is the most diverse of all the

kingdoms.

Protists can be animal-like, plantlike, or funguslike.

• Protists are eukaryotes that are not animals, plants, or

fungi.

• Animal-like protists consume other organisms.

– heterotrophs

– single-celled

• Plantlike protists are photosynthetic.

– single-celled, colonial, or multicellular

– no roots, stems, or leaves

• Funguslike protists decompose dead organisms.

– heterotrophs

– can move, whereas fungi cannot

Protists are difficult to classify.

• Protista is one kingdom in the domain Eukarya.

• Protist classification will likely change.

– Some protists are not closely related.

– Molecular evidence supports reclassification.

19.2 Animal-like Protists

KEY CONCEPT

Animal-like protists are single-celled heterotrophs

that can move.

Animal-like protists move in various ways.

• Animal-like protists are often called protozoa.

macronucleus

food vacuole

oral groove

micronucleus

contractile vacuole

• Protozoa with flagella are zooflagellates.

– flagella help zooflagellates swim

– more than 2000 zooflagellates

• Some protists move with pseudopods.

– change shape as they move

– amoebas

– foraminifera

• Some protists move with pseudopods.

–change shape as they move

– amoebas

• Some protozoa move with cilia.

macronucleus

food vacuole

oral groove

micronucleus

contractile vacuole

– cilia help protists swim and capture food

– more than 8000 ciliates

Some animal-like protists cause disease.

• Protists cause some well-

known infectious diseases. sporozoiteshuman liver

liver cells

developed

parasites

red blood

• Malaria is caused by Plasmodium and spread by mosquitoes.

• Sleeping sickness is caused by Trypanosoma and spread by flies.

• A giardia infection is caused by Giardia and spread through water.

Malaria Infection

19.3 Plantlike Protists

KEY CONCEPT

Algae are plantlike protists.

Plantlike protists can be single-celled or multicellular.

• Photosynthetic plantlike protists are called

algae.

colony

daughter colony

• Euglenoids are a large group of plantlike protists.

pellicle

nucleus

chloroplast

eye spot

contractile

vacuole

flagellum

– mostly photosynthetic

– some heterotrophic

– single-celled

– one or two flagella

• Dinoflagellates are mostly marine plantlike protists.

Dinoflagellates

– have two flagella

– may be bioluminescent

– have stiff protective plates

– can cause red tide

• Diatoms are plantlike protists with glasslike shells.

– shells made of silica

– produce large amounts of oxygen

• Multicellular algae are classified by their pigments.

– Green algae contain

chlorophyll a and b.

– Brown algae contain

chlorophyll c.

– Red algae contain

chlorophyll a and

phycoerythrin.

Many plantlike protists can reproduce both sexually and

asexually.

• All algae can reproduce asexually.

– Multicellular algae can fragment.

– Chlamydomonas divides into zoospores.

• Some algae produce sexually.

– Some species alternate generations.

– Sexual reproduction can be triggered by environmental

stress.

19.4 Funguslike Protists

KEY CONCEPT

Funguslike protists decompose organic matter.

Slime molds and water molds are funguslike protists.

• Slime molds have both funguslike and animallike traits.

– decomposers, like fungi

– can move, like animals

• Slime molds can be plasmodial or cellular.

– Plasmodial slime molds are giant cells with many nuclei.

– Cellular slime molds contain independent cells.

• Water molds are freshwater, funguslike protists.

– one type of water mold caused Great Potato Famine

of Ireland in the 1800’s

– made of branching

strands of cells

– can be parasites of

plants or fish

19.5 Diversity of Fungi

KEY CONCEPT

Fungi are heterotrophs that absorb their food.

Fungi are adapted to absorb their food from the

environment.

• Plants and fungi have different traits.

– Fungal cell walls are made of chitin.

– Plant cell walls are made of cellulose.

– Plants have chlorophyll and photosynthesize.

– Fungi absorb food through hyphae.

• Fungi are multicellular organisms, with the exception of

yeasts.

– hyphae

– mycellium

– fruiting body

Fungi come in many shapes and sizes.

• Primitive fungi are aquatic and have flagellated spores.

• Sac fungi form a reproductive sac, or ascus.

– Yeasts are single-celled sac fungi.

– Morels and truffles are multicellular sac fungi.

• Bread molds are often found on spoiled food.

– form zygospores during reproduction

– mycorrhizae belong to this group

• Club fungi have fruiting bodies which are club-shaped.

– reproductive structures

called basidia

– include mushrooms,

puffballs, and

shelf fungi

Fungi reproduce sexually and asexually.

• Most fungi reproduce both sexually and asexually.

– Yeasts reproduce asexually through budding.

– Yeasts form asci during sexual reproduction.

• Multicellular fungi have complex reproductive cycles.

– distinctive reproductive

structures

– life cycles may include either sexual or asexual reproduction or both

• All fungi form spores and zygotes.

19.6 Ecology of Fungi

KEY CONCEPT

Fungi recycle nutrients in the environment.

Fungi may be decomposers, pathogens, or mutualists.

• Fungi and bacteria are the main decomposers in any

ecosystem.

– decompose dead leaves, twigs, logs, and animals

– return nutrients to the soil

– can damage fruit trees and wooden structures

• Fungi can act as pathogens.

– human diseases include ringworm and athlete’s foot

– plant diseases include Dutch elm disease

• Fungi can act as mutualists.

– lichens form between fungi and algae

– mycorrhizae form between fungi and plants

– relationships form between fungi and some insects

• Fungi can act as mutualists.

Fungi are studied for many purposes.

• Fungi are useful in several ways.

– as food

– as antibiotics

– as model systems for molecular biology

KEY CONCEPT Kingdom Protista is the most diverse...

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