Transcript chapt 21
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.
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Live in a variety of different habitats
Domains eubacteria and archaea
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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.
Domain eubacteria
Identified by
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Their shape
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Metabolic reactions
Chemistry of their cell walls
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Can be rods, spheres or spiral-shaped
Gram (+) and Gram (-)
Bacterial cells structure
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Shapes of bacteria
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Domain eubacteria
Occupy many different ecological niches
Decomposers
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Heterotrophs that break down organic matter
Called saprophytes
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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
Decomposers in sewage
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Domain eubacteria
Commensal bacteria
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Mutualistic +/+
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Bacteria that live on or in
organisms without
benefiting or harming the
host
Normal microflora Bacteria on our skin
E. coli in our large
Domain eubacteria
Mutualistic bacteria
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E. coli in our large intestine
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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
Cyanobacteria
Photosynthetic eubacteria
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Cyanobacteria performs photosynthesis like
plants.
Chlorella
Spirulina
Cyanobacteria
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Domain eubacteria
Bacteria and mineral cycles
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Nitrogen cycle
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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.
Domain eubacteria
Disease-causing bacteria
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Also called pathogens or
parasites +/Some commensalistic bacteria
can become pathogenic.
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If they are given the opportunity to
increase in number
If they have the opportunity to invade
new tissue
Example: S. pneumoniae
A bacterial plant disease
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Domain eubacteria
Control of bacterial populations
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Bacterial populations grow rapidly because
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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
Kingdom protista
A catch-all kingdom
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Divided into three groups
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Includes a diverse array of organisms
Many are not evolutionarily related to one another.
All are eukaryotic
Most are single celled; some are multicellular.
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Algae
Autotrophic, unicellular
Protozoa
Heterotrophic, unicellular
Fungus-like protists
Relationships among members of
the protista
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Algae
Contain chlorophyll and can carry out
photosynthesis
Most are aquatic.
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Plankton float in the water.
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Phytoplankton are photosynthetic.
Zooplankton are heterotrophic.
Algae
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The terrestrial forms live in very moist areas.
Most are unicellular; a few are multicellular.
Single-celled algae
Euglenids
Move by flagella
Have a flexible outer covering called a pellicle
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Gives them a shape
Some are heterotrophs, others are autotrophs.
Many live in freshwater.
Single-celled algae
Diatoms
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Found in freshwater, marine and soil
environments
Major component of phytoplankton
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A few are heterotrophs.
Brownish in color
Do not have cilia or flagella
Have cell walls made of silica
Diatomeous earth
Single-cell algae
Dinoflagellates
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Important primary producers in marine
ecosystems
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Have two flagella
Have outer covering made of cellulose
Most are autotrophs.
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Also occur in freshwater
Some are heterotrophs.
Some are parasitic.
Red tides
Single-cell algae
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Some produce toxins that can kill fish.
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Red tide
Can poison humans if they eat poisoned fish
Some are bioluminescent.
Single-celled algae
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Multicellular algae
Commonly known as seaweed.
Red algae
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Live in warm oceans
Used to produce agar and carrageenin
Red and brown algae
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Multicellular algae
Brown algae
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Green algae
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Live in cooler marine environments
Can grow very long
Produce alginates (food stabilizer)
Found in freshwater ecosystems
Are photosynthetic and have cellulose cell walls
Green algae
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Protozoa
Eukaryotic
Heterotrophic
Unicellular
Lack cell walls
Classified by their means of locomotion
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Flagellates
Ameboid
Ciliates
Apicomplexa
Flagellates
Have flagella
Live in moist environments
Many are mutualistic.
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Many are parasitic .
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Found in termite gut; digest cellulose
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Trichomonas vaginalis-common sexually
transmitted disease
Trypanosomes cause sleeping sickness in
humans and cows.
Giardia causes intestinal distress, diarrhea, gas.
Flagellates
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Amoeboid protozoans
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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
Ameboid protozoa
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Ciliates
Contain cilia
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Beat in an organized, rhythmic fashion to move
the cell
Ruminants have ciliates in their gut.
Termites
Ciliates
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The apicomplexans
Nonmotile parasites
Have a spore-like stage in their life cycle
Malaria is caused by an apicomplexan.
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Transmitted by mosquitoes to humans
Reproduces in the mosquito
Eliminating mosquitoes helps reduce the
incidence of malaria.
The life cycle of Plasmodium vivax
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Funguslike protists
Have a motile
reproductive stage
Slime molds
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Move like amoeba
Digest dead organic
matter
Multicellularity in the protista
Volvox
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Volvox is colonial.
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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
The development of multicellular
green algae
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Kingdom Fungi
Nonphotosynthetic; heterotrophic
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Eukaryotic
Have chitin-containing cell walls
Made up of filaments known as hypha
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Hyphae form networks called mycelium
Disperse through spores
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Secrete enzymes that digest large molecules externally
Cells with tough protective coating
Can be produced by sexual or asexual reproduction
Mycelium
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Fungus taxonomy
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The significance of fungi
Fungi play many roles in ecosystems
Decomposers
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Food
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Fungi and bacteria are the major composers in ecosystems.
Recycles nitrogen, carbon and phosphorus
Can destroy clothes, wood, leather, 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.
The significance of fungi
Mycorrhizae
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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
Mycorrhizae
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Significance of fungi
Lichens
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Symbiotic relationship between a fungus and
either an alga or cyanobacterium.
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Do not require soil for growth
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The alga or cyanobacterium is photosynthetic and
provides food.
The fungus provides a moist environment.
Grow on trees or rocks
Important in soil formation during ecological succession
Lichens
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Significance of fungi
Pathogenic fungi
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Can infect plants
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Can infect humans
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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.
Pneumocystis is present in most people’s lungs.
Can cause infection in people with compromised
immune systems
Corn smut
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Significance of fungi
Toxic fungi
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Some fungi can produce mycotoxins
The mushroom, Amanita spp, makes a toxin that is
deadly. “Death Angel”
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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
Poisonous mushrooms
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