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PowerPoint to accompany

CONCEPTS IN BIOLOGY

Enger • Ross • Bailey

CHAPTER 21

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What are microorganisms?

A tiny organism that cannot be seen without a microscope.– Live in a variety of different habitats

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Domains eubacteria and archaea

Used to be lumped into one group, bacteria Eubacteria have cell walls with

peptidoglycan. Archaea and eubacteria have chemically

unique cell membranes. So different from each other necessary to classify into different Domains of life.

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Domain eubacteria

Identified by– Their shape

Can be rods, spheres or spiral-shaped– Metabolic reactions– Chemistry of their cell walls

Gram (+) and Gram (-)

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Bacterial cells structure

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Shapes of bacteria

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Domain eubacteria Occupy many different ecological niches Decomposers

– Heterotrophs that break down organic matter– Called saprophytes

Can live on dead organic matter– Some are anaerobic. – tetanus, botulism– Others are aerobic and break down organic matter into

carbon dioxide and water.– Important in recycling carbon, nitrogen, phosphorus, etc.– Could be used to break down sewage, clean up oil spills– Used in food production (blue cheese, yogurt, beer, wine,

etc.)– Are responsible for food spoilage

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Decomposers in sewage

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Domain eubacteria

Commensal bacteria +/ø– Bacteria that live on or in

organisms without benefiting or harming the host

Mutualistic +/+– Normal microflora-

Bacteria on our skinE. coli in our large

intestine

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Domain eubacteria

Mutualistic bacteria– E. coli in our large intestine

Produce antibiotics and compete for resources

– Reducing the growth of pathogenic bacteria

They produce and release vitamin K.– Cyanobacteria and fungi in lichens– Plants and nitrogen-fixing bacteria

in their roots

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Cyanobacteria

Photosynthetic eubacteria– Cyanobacteria performs photosynthesis like

plants.ChlorellaSpirulina

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Cyanobacteria

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Domain eubacteria Bacteria and mineral cycles

– Nitrogen cycle Nitrogen-fixing bacteria

transform atmospheric nitrogen into ammonia.

– Ammonia can be used by plants to make amino acids.

– Other bacteria convert ammonia waste to nitrate or nitrite.

– Other bacteria convert nitrite to atmospheric nitrogen.

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Domain eubacteria

Disease-causing bacteria– Also called pathogens or

parasites +/-– Some commensalistic bacteria

can become pathogenic. If they are given the opportunity to

increase in number If they have the opportunity to invade

new tissue Example: S. pneumoniae

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A bacterial plant disease

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Domain eubacteria

Control of bacterial populations– Bacterial populations grow rapidly because

Their generation time is so short.– About every 20 minutes– 1 bacteria can lead to millions in a matter of days

They can generate resistant forms or stages.– Spores

They mutate rapidly.– Can produce antibiotic resistant strains– MRSA, VRE

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Kingdom protista A catch-all kingdom

– Includes a diverse array of organisms– Many are not evolutionarily related to one another.

All are eukaryotic– Most are single celled; some are multicellular.

Divided into three groups– Algae

Autotrophic, unicellular– Protozoa

Heterotrophic, unicellular– Fungus-like protists

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Relationships among members of the protista

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Algae

Contain chlorophyll and can carry out photosynthesis

Most are aquatic.– Plankton float in the water.

Phytoplankton are photosynthetic. Zooplankton are heterotrophic.

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Algae

The terrestrial forms live in very moist areas. Most are unicellular; a few are multicellular.

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Single-celled algae

Euglenids Move by flagella Have a flexible outer covering called a pellicle

– Gives them a shape Some are heterotrophs, others are autotrophs. Many live in freshwater.

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Single-celled algae Diatoms

– Found in freshwater, marine and soil environments

– Major component of phytoplankton A few are heterotrophs.

– Brownish in color– Do not have cilia or flagella– Have cell walls made of silica– Diatomeous earth

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Single-cell algae

Dinoflagellates– Important primary producers in marine

ecosystems Also occur in freshwater

– Have two flagella– Have outer covering made of cellulose– Most are autotrophs.

Some are heterotrophs. Some are parasitic. Red tides

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Single-cell algae– Some produce toxins that can kill fish.

Red tide Can poison humans if they eat poisoned fish

– Some are bioluminescent.

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Single-celled algae

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Multicellular algae Commonly known as seaweed. Red algae

– Live in warm oceans– Used to produce agar and carrageenin

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Red and brown algae

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Multicellular algae

Brown algae– Live in cooler marine environments– Can grow very long– Produce alginates (food stabilizer)

Green algae– Found in freshwater ecosystems– Are photosynthetic and have cellulose cell walls

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Green algae

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Protozoa

Eukaryotic Heterotrophic Unicellular Lack cell walls Classified by their means of locomotion

– Flagellates– Ameboid– Ciliates– Apicomplexa

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Flagellates Have flagella Live in moist environments Many are mutualistic.

– Found in termite gut; digest cellulose Many are parasitic .

– Trichomonas vaginalis-common sexually transmitted disease

– Trypanosomes cause sleeping sickness in humans and cows.

– Giardia causes intestinal distress, diarrhea, gas.

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Flagellates

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Amoeboid protozoans Move via pseudopods

– Cellular extensions in which cytoplasm flows Most are free-living.

– Feed on algae, bacteria, etc. Some are parasitic.

– Amoebic dysentery Examples

– Amoeba

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Ameboid protozoa

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Ciliates

Contain cilia– Beat in an organized, rhythmic fashion to move

the cell Ruminants have ciliates in their gut. Termites

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Ciliates

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The apicomplexans

Nonmotile parasites Have a spore-like stage in their life cycle Malaria is caused by an apicomplexan.

– Transmitted by mosquitoes to humans– Reproduces in the mosquito– Eliminating mosquitoes helps reduce the

incidence of malaria.

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The life cycle of Plasmodium vivax

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Funguslike protists Have a motile

reproductive stage Slime molds

– Move like amoeba– Digest dead organic

matter

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Multicellularity in the protista

Volvox– Volvox is colonial.

The flagella of each cell moves together to move the colony.

Some of the cells are specialized to produce sperm and egg.

Thought to be the ancestor of multicellular organisms

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The development of multicellular green algae

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Kingdom Fungi Nonphotosynthetic; heterotrophic

– Secrete enzymes that digest large molecules externally Eukaryotic Have chitin-containing cell walls Made up of filaments known as hypha

– Hyphae form networks called mycelium Disperse through spores

– Cells with tough protective coating– Can be produced by sexual or asexual reproduction

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Mycelium

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Fungus taxonomy

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The significance of fungi Fungi play many roles in ecosystems Decomposers

– Fungi and bacteria are the major composers in ecosystems.– Recycles nitrogen, carbon and phosphorus– Can destroy clothes, wood, leather, food

Food– Fungi and their products can be used as food.

Mushrooms Soy sauce is made by fermenting an ascomycete. Citric acid in cola is released from a mold. Yeasts are used to make alcoholic beverages and

bread.

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The significance of fungi Mycorrhizae

– Associations between fungi and the roots of plants

– One type penetrates the roots of the plant.– The other type surrounds the roots but doesn’t

penetrate.– Found in 80-90% of all plants– Increases the root’s surface area for absorption of

nutrients up to 10-fold

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Mycorrhizae

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Significance of fungi

Lichens– Symbiotic relationship between a fungus and

either an alga or cyanobacterium. The alga or cyanobacterium is photosynthetic and

provides food. The fungus provides a moist environment.

– Do not require soil for growth Grow on trees or rocks Important in soil formation during ecological succession

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Lichens

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Significance of fungi Pathogenic fungi

– Can infect plants Caused the extinction of Chesnut trees and Dutch elm

trees Causes wheat rust and corn smut

– Causes costly damage to crops– Farmers have to use fungicides.

– Can infect humans Pneumocystis is present in most people’s lungs. Can cause infection in people with compromised

immune systems

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Corn smut

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Significance of fungi Toxic fungi

– Some fungi can produce mycotoxins– The mushroom, Amanita spp, makes a toxin that is

deadly. “Death Angel” Food contaminated with these spores can cause

illness and death.– The mushroom, Psilocybe contains a

hallucinogenic chemical called psilobycin.– Claviceps purpurea is a parasite on rye that

generates a toxin that causes hallucinations, insanity, muscle spasms and death. Witches

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Poisonous mushrooms