Download Bacteria and Viruses

Classification, Bacteria, &
Viruses
Unit 7
Chapter
17
Organizing Life’s Diversity
17.1 The History of Classification
Early Systems of Classification
 Biologists use a
system of
classification to
organize
information about
living things.
Chapter
17
Organizing Life’s Diversity
17.1 The History of Classification
Aristotle’s System
 Aristotle classified organisms as either
animals or plants.
Chapter
17
Organizing Life’s Diversity
17.1 The History of Classification
Linnaeus’s System
 Linnaeus’s system of classification was the
first formal system of taxonomy.
Perching bird
Bird of prey
Wading bird
Chapter
17
Organizing Life’s Diversity
17.1 The History of Classification
Binomial Nomenclature
 Linnaeus’s method of naming organisms,
called binomial nomenclature, gives each
species a scientific name with two parts.
 The first part is the genus name, and the
second part is the species.
Ex. Ursus americanus
Chapter
17
Organizing Life’s Diversity
17.1 The History of Classification
 Biologists use
scientific names
for species
because common
names vary in
different areas of
the world.
Ursus americanus
American black bear
Chapter
17
Organizing Life’s Diversity
17.1 The History of Classification
 When writing a scientific name, scientists use these
rules:
 The first letter of the genus name always is
capitalized, but the rest of the genus name and all
letters of the species are lowercase.
 If a scientific name is written in a printed book or
magazine, it should be italicized.
 When a scientific name is written by hand, both
parts of the name should be underlined.
 After the scientific name has been written
completely, the genus name will be abbreviated to
the first letter in later appearances
(e.g., C. cardinalis).
Chapter
17
Organizing Life’s Diversity
17.1 The History of Classification
Taxonomic Categories
 The taxonomic
categories are part of a
hierarchal system.
 Each category is
contained within
another, and they
are arranged from broadest to most specific.
Chapter
17
Organizing Life’s Diversity
17.1 The History of Classification
Species and Genus
 A named group of organisms is called a taxa.
 A genus is a group of species that are closely
related and share a common ancestor.
Chapter
17
Organizing Life’s Diversity
17.1 The History of Classification
Family
 A family is the next higher taxon, consisting
of similar, related genera.
Chapter
17
Organizing Life’s Diversity
17.1 The History of Classification
Higher Taxa
 An order contains related families.
 A class contains related orders.
 A phylum contains related classes.
 The taxon of related phyla or divisions is a
kingdom.
 The domain is the broadest of all the taxa and
contains one or more kingdoms.
Grizzly bear
Black bear
Giant
panda
Red fox
Abert
squirrel
Coral
snake
Sea star
KINGDOM Animalia
PHYLUM Chordata
CLASS Mammalia
ORDER Carnivora
FAMILY Ursidae
GENUS Ursus
SPECIES Ursus arctos
Chapter
17
Organizing Life’s Diversity
17.2 Modern Classification
Typological Species Concept
 Aristotle and Linnaeus thought of each
species as a distinctly different group of
organisms based on physical similarities.
Chapter
17
Organizing Life’s Diversity
17.2 Modern Classification
Biological Species Concept
 The biological species concept a species
as a group of organisms that is able to
interbreed and produce fertile offspring in a
natural setting.
Chapter
17
Organizing Life’s Diversity
17.2 Modern Classification
Phylogenic Species Concept
 Phylogeny is the evolutionary history of a
species.
 The phylogenic species concept shows
evidence of a pattern of ancestry and
descent.
Chapter
17
Organizing Life’s Diversity
17.2 Modern Classification
Morphological Characters
 Shared morphological characters suggest that
species are related closely and evolved from a
recent common ancestor.
 Analogous characters  the same function
but different underlying construction.
 Homologous characters  different functions, but
show an anatomical similarity inherited from a
common ancestor.
Chapter
17
Organizing Life’s Diversity
17.2 Modern Classification
Biochemical Characters
 Scientists use biochemical characters, such
as amino acids and nucleotides, to help
them determine evolutionary relationships
among species.
 DNA and RNA analyses are powerful tools
for reconstructing phylogenies.
Chapter
17
Organizing Life’s Diversity
17.2 Modern Classification
Phylogenetic Reconstruction
 Cladistics reconstructs phylogenies based on
shared characters.
 Scientists consider two main types of characters
when doing cladistic analysis.
 An ancestral character is found within the entire
line of descent of a group of organisms.
 Derived characters are present members of one
group of the line but not in the common ancestor.
Chapter
17
Organizing Life’s Diversity
17.2 Modern Classification
Cladograms
 The greater the
number of derived
characters shared
by groups, the
more recently the
groups share a
common ancestor.
Section 18-2
Traditional Classification Versus Cladogram
Appendages
Crab
Conical Shells
Barnacle
Limpet
Crustaceans
Crab
Barnacle
Gastropod
Limpet
Molted
exoskeleton
Segmentation
CLASSIFICATION
BASED ON VISIBLE
SIMILARITIES
Tiny free-swimming larva
CLADOGRAM
Chapter
17
Organizing Life’s Diversity
17.3 Domains and Kingdoms
Grouping Species
 The three domains are
Bacteria, Archaea, and
Eukarya.
 The six kingdoms are
Bacteria, Archaea, Protists,
Fungi, Plantae, and
Animalia.
Chapter
17
Organizing Life’s Diversity
17.3 Domains and Kingdoms
Domain Bacteria
 Eubacteria are
prokaryotes whose cell
walls contain
peptidoglycan.
Chapter
17
Organizing Life’s Diversity
17.3 Domains and Kingdoms
Domain Archaea
 Archaea are thought to be more ancient than
bacteria and yet more closely related to our
eukaryote ancestors.
 They are called extremophiles because
they can live in extreme environments.
Chapter
17
Organizing Life’s Diversity
17.3 Domains and Kingdoms
Domain Eukarya
 All eukaryotes are classified in Domain
Eukarya.
 Domain Eukarya contains Kingdom
Protista, Kingdom Fungi, Kingdom Plantae,
and Kingdom Animalia.
Chapter
17
Organizing Life’s Diversity
17.3 Domains and Kingdoms
Kingdom Protista
 Protists are eukaryotic organisms that can
be
unicellular, colonial,
or multicellular.
 Protists are
classified into three
different groups—
plantlike, animallike, and
funguslike.
Chapter
17
Organizing Life’s Diversity
17.3 Domains and Kingdoms
Kingdom Fungi
 A fungus is a unicellular or multicellular
eukaryote that
absorbs
nutrients from organic
materials in its
environment.
 Member of Kingdom
Fungi are
heterotrophic, lack motility, and have cell
walls.
Chapter
17
Organizing Life’s Diversity
17.3 Domains and Kingdoms
Kingdom Plantae
 Members of Kingdom Plantae form the base
of all terrestrial habitats.
 All plants are
multicellular and have
cell walls composed of
cellulose.
 Most plants are
autotrophs, but some are heterotrophic.
Chapter
17
Organizing Life’s Diversity
17.3 Domains and Kingdoms
Kingdom Animalia
 All animals are heterotrophic, multicellular
eukaryotes.
 Animal organs often are
organized into complex
organ systems.
 They live in the water,
on land, and in the air.
Chapter
17
Organizing Life’s Diversity
17.3 Domains and Kingdoms
Chapter
18
Bacteria and Viruses
18.1 Bacteria
Diversity of Prokaryotes
 Bacteria are microscopic organisms that are
prokaryotes.
 Prokaryotes are divided into two domains—
the Domain Bacteria (eubacteria) and the
Domain Archaea (archaebacteria).
Chapter
18
Bacteria and Viruses
18.1 Bacteria
Photosyntheti
c
eubacteria
Archaebacteria Eubacteria
magnification
unavailable
9560x
3000x
Chapter
18
Bacteria and Viruses
18.1 Bacteria
Eubacteria
 Very strong cell walls
 Contain peptidoglycan
 Some have a second cell wall
Chapter
18
Bacteria and Viruses
18.1 Bacteria
Archaebacteria
 Thermoacidophiles (thur muh uh SIH duh
filz) live in hot, acidic environments.
 Halophiles (HA luh filz) live in very salty
environments.
 Methanogens (meh THAHN oh jenz) cannot
live in the presence of oxygen.
Chapter
18
Bacteria and Viruses
18.1 Bacteria
Differences Between Eubacteria and
Archaebacteria
 The cell walls of the eubacteria contain
peptidoglycan, but the cell walls of
archaebacteria do not.
 The two groups of organisms have different
lipids in their plasma membranes.
 Different ribosomal proteins and RNA
Chapter
18
Bacteria and Viruses
18.1 Bacteria
Prokaryote Structure
 Prokaryotes are
microscopic,
unicellular
organisms.
 They have some characteristics of all cells,
such as DNA and ribosomes.
 Lack a nuclear membrane and other
membrane-bound organelles
Chapter
18
Bacteria and Viruses
18.1 Bacteria
 Chromosomes
 Capsule
 Pili
 Size
Chapter
18
Bacteria and Viruses
18.1 Bacteria
Identifying Prokaryotes
 Shape
 Spherical = Cocci
 Rod-shaped = Bacilli
 Spiral-shaped = Spirochetes
Spirochete
s
Bacilli
Cocci
400x
5460x
2000x
Identified by shape, cell wall, method of movement,
and how they obtain food
•Shapes –
•Bacilli = rod
•Cocci – round
•Spirilla – spiral
•Prefixes – strep = long chains, staph = clumps, diplo = pairs
Chapter
18
Bacteria and Viruses
18.1 Bacteria
Cell Walls
 Eubacterial cells have peptidoglycan.
 Dyes added to the bacteria identify those
with and those without an outer layer of
lipid.
Purple = gram positive
cell wall contains peptidoglycan
Chapter
18
Bacteria and Viruses
18.1 Bacteria
Movement
 Prokaryotic flagella are made of filaments.
 Flagella help prokaryotes to move toward
materials that they need to survive.
Chapter
18
Bacteria and Viruses
18.1 Bacteria
Reproduction of Prokaryotes
 Binary Fission
 Division of a cell into two
genetically identical cells
 Conjugation
 Two prokaryotes attach to each other
and exchange genetic information.
Chapter
18
Bacteria and Viruses
18.1 Bacteria
Photoautotrophs
 Carry out photosynthesis in a similar manner
as plants
Chemoautotrophs
 Break down and release inorganic compounds
that contain nitrogen or sulfur
Aerobes and Anaerobes
 Obligate aerobes are bacteria that require oxygen
to grow.
 Anaerobic bacteria do not use oxygen for growth
or metabolism.
Chapter
18
Bacteria and Viruses
18.1 Bacteria
Survival of Bacteria
 Endospores
 Resistant to harsh
environments and might be
able to survive extreme
heat, extreme cold,
dehydration, and large
amounts of ultraviolet
radiation
Chapter
18
Bacteria and Viruses
18.1 Bacteria
Mutations
 Bacteria reproduce quickly and their
population grows rapidly.
 Mutations lead to new forms of genes, new
gene combinations, new characteristics, and
genetic diversity.
Chapter
18
Bacteria and Viruses
18.1 Bacteria
Ecology of Bacteria
 Nutrient cycling and nitrogen fixation
 Bacteria are decomposers, returning vital
nutrients to the environment.
 Nitrogen-fixing bacteria live in a symbiotic
relationship in the root nodules of plants
such as soybeans, clover, and alfalfa.
Chapter
18
Bacteria and Viruses
18.1 Bacteria
Normal Flora
 Most of the bacteria that live in or on you
are harmless and are called normal flora.
21,674x
E. coli
Chapter
18
Bacteria and Viruses
18.1 Bacteria
Foods and Medicines
 Some foods are made with the aid of
bacteria.
 cheese
 yogurt
 buttermilk
 pickles
 vitamins
Chapter
18
Bacteria and Viruses
18.1 Bacteria
Disease-causing Bacteria
 A small percentage of bacteria cause
disease.
 Bacteria multiply quickly at the site of
infection.
 Bacteria secrete a toxin.
Chapter
18
Bacteria and Viruses
18.2 Viruses and Prions
Viruses
 A nonliving strand of genetic
material within a protein coat
 No organelles to take in
nutrients or use energy
 Cannot make proteins
 Cannot move
 Cannot replicate on their own
Chapter
18
Bacteria and Viruses
18.2 Viruses and Prions
Viral Infection
 In order to replicate, a virus must enter a
host cell.
 The virus attaches to the host cell using
specific receptors on the plasma
membrane.
 Many viruses cannot be transmitted
between different species.
Chapter
18
Bacteria and Viruses
18.2 Viruses and Prions
Lytic Cycle
 The host cell makes many copies of the
viral RNA or DNA.
Lysogenic Cycle
 Viral DNA inserts, or integrates into a
chromosome in a host cell.
 Infected cell will have the viral genes
permanently.
Chapter
18
Bacteria and Viruses
18.2 Viruses and Prions
Chapter
18
Bacteria and Viruses
18.2 Viruses and Prions
Retroviruses
 Viruses that have RNA instead of DNA for
their genetic material
 Retroviruses have a protein capsid.
 Lipid envelope is obtained from the
plasma membrane of a host cell
Chapter
19
Protists
19.1 Introduction to Protists
Protists
 All protists are eukaryotes.
 Some reproduce asexually by mitosis
while others exchange genetic material
during meiosis.
Chapter
19
Protists
19.1 Introduction to Protists
Classifying Protists
 Some scientists classify protists by their
methods of obtaining nutrition.
 Animal-like protists
 Plantlike protists
 Funguslike protists
Chapter
20
Fungi
20.1 Introduction to Fungi
Major Features of Fungi
 Cell wall composed of chitin
 Hyphae form a netlike mass called a
mycelium.
 Hyphae provide
a larger surface
area for nutrient
absorption.
Chapter
20
Fungi
20.1 Introduction to Fungi
Spore Production
 The asexual and sexual life cycle of most
fungi includes spore production.
 A spore develops into a new organism
without the fusion of gametes.
 Spores produce new hyphae that form a
mycelium.
Chapter
21
Introduction to Plants
21.1 Plant Evolution and Adaptations
Stomata
 Enable the exchange
of gases on a plant
 Openings in the outer
cell layer of leaves
and some stems
Chapter
21
Introduction to Plants
21.1 Plant Evolution and Adaptations
Vascular Tissues
 Vascular tissue enables faster
movement of substances than by
osmosis and diffusion, and over greater
distances.
 Vascular tissue provides support and
structure, so vascular plants can grow
larger than nonvascular plants.
Chapter
21
Introduction to Plants
21.1 Plant Evolution and Adaptations
Seeds
 A plant structure that
contains an embryo,
contains nutrients for the
embryo, and is covered
with a protective coat
 These features enable
seeds to survive harsh environmental conditions
and
then sprout when favorable conditions exist.
Chapter
22
Plant Structure and Function
22.1 Plant Cells and Tissues
Vascular Tissue
 Xylem
 Transports
substances away
from the roots
 Composed of
specialized cells
called vessel elements and tracheids
Chapter
22
Plant Structure and Function
22.1 Plant Cells and Tissues
Phloem
 Transports dissolved
sugars and other
organic compounds
throughout the plant.
Chapter
23
Reproduction in Plants
23.2 Flowers
Flower Organs
Chapter
24
Introduction to Animals
24.1 Animal Characteristics
Support
 Invertebrates
 Exoskeletons
 Hard or tough outer coverings that
provide a framework of support
Chapter
24
Introduction to Animals
24.1 Animal Characteristics
Support
 Vertebrates
 Endoskeletons
 Provide support for the body
 Provide an internal brace for muscles
to pull against
Chapter
24
Introduction to Animals
24.2 Animal Body Plans
Symmetry
 Similarity or balance among body structures of
organisms
 Asymmetry
 Radial symmetry
 Bilateral symmetry
Kingdom Protista
Ch. 20-1 and 2
What is a protist?
• Eukaryotes that don’t fit in
the other kingdoms
• Very diverse kingdom –
200,000 species
• Most are unicellular
• Protist = “the very first” –
first eukaryotes on earth
• 3 main groups based on
how they obtain food
Animal-like protists
• Heterotrophs
• “protozoans” = first animals
• 4 phyla (groups) based on mode of
movement
Zooflagellates
• Swim with use of flagella
• Flagella – long whip-like
projection used to propel an
organism
• Live in lakes and streams
• Absorb food through cell
membrane
• Reproduce asexually
through binary fission
• i.e. euglena
Sarcodines
• Move and feed through use of
pseudopods
• Pseudopod – temporary
projection of the cytoplasm
• i.e. Amoebas
• When feeding, they surround
food and bring into cell in the
form of a food vacuole
Ciliates
• Use cilia for feeding and
movement
• Cilia – hair-like projections
that flow back and forth like
ores
• i.e. Paramecium
• Contain macro (working
copy) and micronucleus
(reserve copy of genetic
info)
• Food is swept into the
gullet where it is forced into
food vacuoles
Sporozoans
• Don’t move on their own and are parasites
Malaria sporozoite
Zooflagellates and
disease
• Malaria – effects 300-500 million
people
– Caused by the sporozoan
Plasmodium
– Carried by the female Anopheles
mosquito
– Infection cycle – mosquito bites
human, saliva and plasmodium
sporozites enter blood,
plasmodium infects liver and red
blood cells, red blood cells burst
dumping toxins into bloodstream
• African sleeping sickness –
– Caused by zooflagellate
Trypanosoma
– Spread by the bite of the Tsetse
fly
– Effects the nervous system
causing loss of consciousness
and coma
• Amebic dysentery –
– Caused by Entamoeba in
contaminated water
Kingdom Fungi
Ch. 21
What are fungi?
• Eukaryotic heterotrophs
that have cell walls
made of chitin
• Chitin – complex
carbohydrate
• Digest food outside their
bodies and absorb the
nutrients
• Some absorb from
decaying matter others
are parasites and absorb
from a host
Fungi structure and function
• All but yeasts are multicellular
• Hyphae – tiny filaments in
the fungi made of 1 cell
• Mycelium- many hyphae
tangled together in a mass
underground
• Fruiting body – reproductive
structure above ground
• Often clusters of fruiting
bodies belong to same
mycelium
Fruiting body
hyphae
mycellium
Fungi reproduction
• Asexually and sexually
• Asexual –
– parts of hyphae break off and
grow on their own
– Spores – released from
sporangiophores into the air
and will settle and grow on their
own
– Fungi spread by spores, spores
grown when environmental
conditions are right
• Sexual – two hyphae (+ and ) meet and form a gamete
Figure 21-5 The Life Cycle of Rhizopus
Section 21-2
Zygospore
(2N)
FERTILIZATION
Sporangium
Gametangia
MEIOSIS
Sporangium
Spores
(N)
Zygospore (2N)
Spores (N)
Stolons
+ Mating type (N)
- Mating type (N)
Sporangiophore
Asexual
Reproduction
Rhizoids
Sexual Reproduction
Diploid
Haploid
How are fungi classified?
• According to structure and method of
reproduction
• 4 groups
– Common Molds - Grow on meat, cheese, and
breads
– Sac Fungi – larges phylum, yeasts
– Club Fungi – club shaped cap to mushroom, some
edible but many are poisonous
– Imperfect fungi – fungi that don’t fit in any other
phylum (penicillium)
Kingdom Plantae
Chapter 22
What are plants?
• Multi-cellular eukaryotes
• Cell walls made of
cellulose.
• Develop from multi-cellular
embryos
• Carry out photosynthesis
using green pigments
chlorophyll a & b
Survival Requirements…
•
•
•
•
Sunlight
water/minerals
gas exchange
movement of
water and
nutrients
Bryophytes
• Need water for reproduction
• No vascular tissue—water by
osmosis
– Can move few centimeters
above the ground
• Small in size
• i.e. mosses, liverworts, and hornworts.
• adapted to environments with
wet habitats and nutrient-poor
soils.
• No true roots
• have rhizoids—long, thin cells
– anchor them in the ground
– absorb water & minerals from the
surrounding soil.
Seedless Vascular Plants
• Plants containing
vascular tissues
– Specialized to conduct
water and nutrients through
the body of the plant.
• True roots, leaves, and
stems
• Ferns & horsetails
• Developed phloem &
xylem
Movement in plants
• Xylem
– Tissue that carries water
upward from the roots to
every part of the plant.
– Tracheids are the key
cells in xylem
• Hollow cells with thick
cell walls that resist
pressure
• Phloem
– Transports solutions of
nutrients and carbs
produced by
photosynthesis
Seed Plants
• Two groups
– Gymnosperms
– Angiosperms
• Gymnosperms
– seeds on surface of
cones
• Angiosperms
– i.e. flowering plants
– seed within a layer of
tissue that protects it.
• Reproduce without
water!
Angiosperms—Flowering Plants
• Reproductive organs: Flowers!
– Contain ovaries that surround/protect seeds
– Monocots: one seed leaf, or cotyledon
• i.e. corn, wheat, lilies, orchids, and palms
– Dicots: two seed leaves, or cotyledons
• i.e. roses, clover, tomatoes, oaks, and daisies
Parts of Plants
• Roots, stems, and leaves
– Roots: tap roots & fibrous
roots; absorb water,
nutrients, minerals;
anchor plants
– Stems: support plant
body, transport nutrients,
contains vascular system
(made of xylem and
phloem)
– Leaves: Site of
photosynthesis; Absorbs
light
Tap Root
Plant Responses
• Phototropism – Plant
movement towards
light
Kingdom Animalia
Survey of organisms
Chs. 26-32
What is an Animal?
• An animal is a
multicellular,
eukaryotic
heterotroph whose
cells lack cell walls
How are they classified?
• Invertebrates
– Animals that have no backbone, or vertebral column.
– 95% of animals
– i.e. insects, worms, jellyfish, sea stars
• Vertebrates
– Animals that have a backbone
– 5% of animals
– i.e. fish, amphibians, reptiles, birds, mammals
Essential Functions
• Feeding
• Respiration
– Oxygen in
– Carbon Dioxide out
• Circulation
– Circulatory system
– Diffusion
• Excretion
– Bi-product of metabolism
• Response
– Nervous system
• Movement
– Skeleton & Muscles
• Reproduction
– Sexual or Asexual
Circulatory
system or
diffusion
Phylum Chordata
• What are chordates?
– Animal that has for some stage of its life:
•
•
•
•
Dorsal (back), hollow nerve cord
Pharyngeal slits
Post-anal tail
A notochord
– Most are vertebrates, but not all!
• i.e. tunicates, lancelets, sponges
Mammalia
• What are they?
– Animals that have hair, ability to nourish
young (milk), breath air, four-chambered
hearts, endotherms.
– Endotherm: animal that generates body heat
internally
– Feeding: herbivores, carnivores, omnivores,
filter feeders.
Maintaining Homeostasis
• Endothermy
– Organism that maintains an internal
temperature by generating its own body heat
from within
• Example?
• Ectothermy
– Organism that relies on interactions with the
environment to help control body temperature
• Example?
Unit 7 Ch. 19.1-2
Bacteria
Prokaryotes
•
•
•
•
•
Single cell
No true nucleus
few organelles
Archaebacteria – extreme environments
Eubacteria
Eubacteria
• Wide variety of bacteria with different
lifestyles
• Cell wall for protection from injury – also
determines the shape of bacteria
• E. Coli – lives in mammal intestines
Section 19-1
The Structure of a Eubacterium
Ribosome
Cell wall
Cell membrane
Capsule
Flagellum
Go to
Section:
DNA
Pili
Archaebacteria
• Cell walls made from different materials
than eubacteria
• Cell membrane lipids different from
eubacteria
• DNA sequences are more like eukaryotes
than eubacteria
• Live in extreme environments like: great
salt lake, hot springs, oxygen deprived
mud
Identifying prokaryotes
• Identified by shape, cell
wall, method of movement,
and how they obtain food
• Shapes –
–
–
–
–
Bacilli = rod
Cocci – round
Spirilla – spiral
Prefixes – strep = long
chains, staph = clumps,
diplo = pairs
Cell walls
• Chemical make-up determined by a gram
stain (purple or red)
– Peptidoglycan = purple, gram positive
– Outer layer of lipid and carbohydrates = pink,
gram negative
Movement
•
•
•
•
Flagella – whip-like structure
Snake type movement
Move in a slime they secrete
Do not move at all
Obtaining energy
• Autotrophs – some carry out
photosynthesis and others carry out
chemosynthesis
• Heterotrophs – “eat” food – (food spoilage)
• Photoheterotrophs – get energy using both
methods above
Releasing energy
• Obligate aerobes – carry
out cellular respiration
with oxygen
• Obligate anaerobes –
cannot live in presence
of oxygen
– Clostridium botulinum botulism
• Facultative anaerobes –
can live with or without
oxygen
Growth and Reproduction
• Binary fission – DNA replicated and splits
in half – asexual
• Conjugation – genetic info exchange
between cells
Unit 9
Bacteria in Nature
Bacteria’s importance
• Vital to living
world
• Photosynthetic
producers
putting oxygen
into air
• Decomposers of
dead matter to
allow recycling of
nutrients
Decomposers
• Break down of dead matter
• Helps to recycle nutrients in the
ecosystem
• Play an important role in sewage
treatment
• Produces purified water, nitrogen, carbon
dioxide gases, and byproducts to be used
as fertilizers
Nitrogen fixers
• Plants depend on nitrogen to
make amino acids and proteins
→animals get nitrogen from
plant proteins
• Nitrogen from atmosphere
must be converted to ammonia
NH3 before plants can use it
– This is done by “nitrogen-fixing”
bacteria
– Symbiotic relationship between
plants and bacteria -
Rhizobium
Bacteria and disease
• Pathogens – disease causing
agents (small percentage of
bacteria)
• Treated with antibiotics – block
the growth and reproduction of
bacteria
• Cause disease in two ways
– Break down tissue for food
• Tuberculosis
– Release toxins that harm the body
• Food poisoning
• Strep throat – scarlet fever =
streptococcus
Lung infection
Human use for bacteria
• Manufacturing food – cheese, buttermilk,
yogurt, sour cream
• Digesting oil spills
• Water treatment
• Medicines
• warfare
Anthrax
Controlling bacteria
• Sterilization – destroy bacteria by
subjecting them to great heat or chemical
action
– Disinfectants – chemical solution that kills
bacteria
– Refrigeration – bacteria grows more slowly in
cold temps. – food
– Boiling at high temps to kill bacteria
– Salt, vinegar, sugar
virus
Living or not?
11/5/2012
Virus (latin for
poison)
• Requires host cell to reproduce-intracellular parasite
• Don’t move, respire, or grow – no
independent metabolism
• smaller than tiniest bacteria
• possess either DNA or RNA
• may be inactive indefinitey
• mutates rapidly
• Named for disease caused, organ
infected , or region detected in
structure
• Contain a nucleic acid
and protein
• HEAD region
– Capsid--protein coat with
nucleic acid core
• TAIL region
– to attach to bacteria/cells
Viral recognition and attachment
• Virus must recognize specific
receptor site on host cell
• Part of virus matches site on
host, lands and locks in
• Attachment is specific- virus
can only enter and reproduce in
a few types of cells
• I. E. - tobacco mosaic virus
cannot infect human cells even
though we are exposed to it
daily
Figure 19-9 Virus Structures
Section 19-2
Tobacco Mosaic
Virus
T4 Bacteriophage
Head
DNA
Influenza
Virus
RNA
Capsid
proteins
Capsid
RNA
Tail
sheath
Tail
fiber
Surface
proteins
Membrane
envelope
Reproduction
• Must take place inside a
host cell
• Infection--chance contact
• Lytic Infection –
– Viral DNA takes over host
nucleus, produces new
viruses
– Lysis of host cell – bursts
and dies – new viruses are
released
Alternate reproduction
• Lysogenic cycle (infection) – virus attacks
cell but doesn’t kill immediately
• Viral DNA mixes with host DNA =
prophage
• Doesn’t always reproduce right away, cell
may function normally
• Viral DNA activates and viral reproduction
begins
Figure 19-10 Lytic and Lysogenic Infections
Figure 19-11 Viruses and Cells
Section 19-2
Pathogenic viruses
•
•
•
•
•
•
•
•
Ebola zaire-AIDS
rhinoviruses
influenza
measles, mumps, chicken pox
polio
rabies
smallpox
Vaccines
• “cow pox”--Edward Jenner
– 1796