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Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
PowerPoint® Lecture Presentations for
Biology
Eighth Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp
BIG IDEA II Biological systems utilize free energy and molecular building blocks
to grow, to reproduce and to maintain dynamic homeostasis.
Enduring Understanding 2.D Growth and dynamic homeostasis of a biological system
are influenced by changes in the system’s environment.
Essential Knowledge 2.D.1 All biological systems from cells and organisms to populations,
communities and ecosystems are affected by complex biotic and abiotic
interactions involving exchange of matter and free energy.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Essential Knowledge 2.D.1: All biological systems from cells and
organisms to populations, communities and ecosystems are affected by complex biotic and abiotic interactions involving exchange of matter and free energy.
• Learning Objectives:
– (2.22) The student is able to refine scientific models and
questions about the effect of complex biotic and abiotic
interactions on all biological systems, from cells and organisms to
populations, communities and ecosystems.
– (2.23) The student is able to design a plan for collecting data to
show that all biological systems (cells, organisms, populations,
communities and ecosystems) are affected by complex biotic and
abiotic interactions.
– (2.24) The student is able to analyze data to identify possible
patterns and relationships between a biotic or abiotic factor and
a biological system (cells, organisms, populations, communities
and ecosystems).
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cell activities are affected by interactions with biotic and abiotic factors.
• Illustrative examples of biotic factors include:
– Cell density
– Biofilms
• Illustrative examples of abiotic factors include:
– Temperature
– Water availability
– Sunlight
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cell Density
• In addition to many internal chemical factors, studies
using animal cells in culture have led to the
identification of many external factors, both chemical
and physical, that can influence cell division and
therefore control cell density.
• Contact cell cycle control mechanisms include density-
dependent inhibition and anchorage dependence.
– In density-dependent inhibition, crowded cells stop dividing.
– Anchorage dependence is a phenomenon in which cells must
be attached to a substratum (i.e. extracellular matrix of a tissue) in
order to divide.
Fig. 12-19
Anchorage dependence
Density-dependent inhibition
Density-dependent inhibition
(a) Normal mammalian cells (b) Cancer cells
25 µm 25 µm
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Biofilms
• Metabolic cooperation between different
prokaryotic species often occurs in surface-
coating colonies known as biofilms.
– Cells in a biofilm secrete signaling molecules that
recruit nearby cells, causing the colonies to grow.
– The cells also produce proteins that stick the cells
to the substrate and to one another.
– Channels in the biofilm allow nutrients to reach
cells in the interior and wastes to be expelled.
Fig. 11-3
Individual rod- shaped cells
Spore-forming structure (fruiting body)
Aggregation in process
Fruiting bodies
0.5 mm
1
3
2
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Organism activities are affected by interactions with biotic and abiotic factors.
• Illustrative examples of biotic factors include:
– Symbiosis
– Predator-prey relationships
• Illustrative examples of abiotic factors include:
– Water/nutrient availability
– Temperature
– Salinity
– pH
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Symbiosis
• Symbiosis is a relationship where two or more
species live in direct and intimate contact with one
another.
– Parasitism
– Mutualism
– Commensalism
Fig. 54-UN2
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Predator-Prey Relationships
Predation is a type of density-dependent population control whereby there
is a biological interaction where a predator (an animal that is hunting)
feeds on its prey (the animal that is attacked).
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 53-19
Wolves Moose
2,500
2,000
1,500
1,000
500
Nu
mb
er
of
mo
os
e
0
Nu
mb
er
of
wo
lve
s
50
40
30
20
10
0 1955 1965 1975 1985 1995 2005
Year
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The stability of populations, communities and ecosystems is affected by interactions with biotic and abiotic factors.
• Illustrative examples of biotic factors include:
– Food chains & food webs
– Species diversity
– Population density
– Algal blooms
• Illustrative examples of abiotic factors include:
– Water & nutrient availability
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Food Chains & Food Webs
• Trophic structure is the feeding relationships
between organisms in a community – it is a key
factor in community dynamics.
– Food chains link trophic levels from producers
to top carnivores.
– A food web is a branching food chain with
complex trophic interactions.
Fig. 54-11
Carnivore
Carnivore
Carnivore
Herbivore
Plant
A terrestrial food chain
Quaternary consumers
Tertiary consumers
Secondary consumers
Primary consumers
Primary producers
A marine food chain
Phytoplankton
Zooplankton
Carnivore
Carnivore
Carnivore
Fig. 54-12
Humans
Smaller toothed whales
Baleen whales
Sperm whales
Elephant seals
Leopard seals
Crab-eater seals
Birds Fishes Squids
Carnivorous plankton
Copepods Euphausids (krill)
Phyto- plankton
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Limits on Food Chain Length
• Each food chain in a food web is usually only a
few links long
• Two hypotheses attempt to explain food chain
length: the energetic hypothesis and the dynamic
stability hypothesis
– The energetic hypothesis suggests that length is
limited by inefficient energy transfer
– The dynamic stability hypothesis proposes that long
food chains are less stable than short ones
– Most data support the energetic hypothesis
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Limits on Food Chain Length: Energetic Hypothesis
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Limits on Food Chain Length: Dynamic Stability Hypothesis
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Species Diversity
• Species diversity of a community is the variety of organisms that make up the community
• It has two components: species richness and relative abundance
– Species richness is the total number of different species in the community
– Relative abundance is the proportion each species represents of the total individuals in the community
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 54-9
Community 1 A: 25% B: 25% C: 25% D: 25%
Community 2 A: 80% B: 5% C: 5% D: 10%
A B C D
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Species Diversity & Ecosystem Stability
• There is growing evidence that the functioning of ecosystems is linked
to biodiversity. Species play essential roles in ecosystems, so local
and global species losses could threaten the stability of the ecosystem.
• There is currently great concern about the stability of both natural and
human-managed ecosystems, particularly given the myriad global
changes already occurring.
• Stability can be defined in several ways, but the most intuitive definition
of a stable system is one having low variability (i.e., little deviation from
its average state) despite shifting environmental conditions.
• Resilience is a somewhat different aspect of stability indicating the
ability of an ecosystem to return to its original state following a
disturbance or other perturbation.
• Diverse ecosystems are more likely to return to a state of stability
following a disturbance than less diverse systems.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Population Density
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Algal Blooms
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
PowerPoint® Lecture Presentations for
Biology
Eighth Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp
BIG IDEA II Biological systems utilize free energy and molecular building blocks
to grow, to reproduce and to maintain dynamic homeostasis.
Enduring Understanding 2.D
Growth and dynamic homeostasis of a biological system
are influenced by changes in the system’s environment.
Essential Knowledge 2.D.2
Homeostatic mechanisms reflect both common ancestry and
divergence due to adaptation in different environments.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Essential Knowledge 2.D.2: Homeostatic mechanisms reflect both
common ancestry and divergence due to adaptation in different environments.
• Learning Objectives:
– (2.25) The student can construct explanations based on
scientific evidence that homeostatic mechanisms reflect
continuity due to common ancestry and/or divergence due to
adaptation in different environments.
– (2.26) The student is able to analyze data to identify
phylogenetic patterns or relationships, showing that
homeostatic mechanisms reflect both continuity due to
common ancestry and change due to evolution in different
environments.
– (2.27) The student is able to connect differences in the
environment with the evolution of homeostatic mechanisms.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Continuity of homeostatic mechanisms reflects common ancestry, while changes may occur in response to different environmental conditions.
• Structural and functional evidence supports the
relatedness of all domains and the evolution of all
organisms. This evidence can be seen in the following
mechanisms:
– Organisms have various mechanisms for obtaining
nutrients and eliminating wastes (divergence).
– Homeostatic control systems in species of microbes,
plants and animals support common ancestry
(relatedness).
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Organisms have various mechanisms for obtaining nutrients and eliminating wastes.
• Illustrative examples include:
– Gas exchange in aquatic and terrestrial plants.
– Digestive mechanisms in animals such as food
vacuoles, gastrovascular cavities, one-way
digestive systems.
– Respiratory systems of aquatic and terrestrial
animals.
– Nitrogenous waste production and elimination
in aquatic and terrestrial animals.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Gas Exchange in Aquatic v. Terrestrial Plants
In aquatic plants, diffusion of O2 &
CO2 occurs across thin membranes
in leaves of aquatic plants.
In terrestrial plants, guard cells
control the opening and closing of
stomata in terrestrial plants.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Osmoregulation and Excretion
• Osmoregulation is the process by which animals
control solute concentrations and balance water
gain and loss.
– It is based largely on controlled movement of solutes
between internal fluids and the external environment.
• Excretion gets rid of metabolic wastes.
– Most metabolic wastes must be excreted from the
body. One of the most important types is nitrogenous
wastes from the breakdown of proteins and nucleic
acids.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Proteins Nucleic acids
Amino acids Nitrogenous bases
–NH2
Amino groups
Most aquatic
animals, including
most bony fishes
Mammals, most
amphibians, sharks,
some bony fishes
Many reptiles
(including
birds), insects,
land snails
Ammonia Urea Uric acid
NH3 NH2
NH2 O C
C
C N
C O N
H H
C O
N C
HN
O H
Nitrogenous Waste Production & Elimination in Aquatic v. Terrestrial Animals
• An animal’s nitrogenous wastes
reflect its phylogeny and habitat.
• The type and quantity of an
animal’s waste products may
have a large impact on its water
balance.
• Among the most important
wastes are the nitrogenous
breakdown products of proteins
and nucleic acids.
Figure 44.8
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Forms of Nitrogenous Wastes
• Animals that excrete nitrogenous wastes as ammonia need
access to lots of water:
– Ammonia is released across the whole body surface or through
the gills.
• The liver of mammals and most adult amphibians converts
ammonia to less toxic urea which is carried to the kidneys
in a concentrated form:
– Urea is excreted with a minimal loss of water.
• Insects, land snails, and many reptiles, including birds
excrete uric acid as their major nitrogenous waste:
– Uric acid is largely insoluble in water and can be secreted as a
paste with little water loss.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Homeostatic control systems in species of microbes, plants and animals support common ancestry.
• Illustrative examples include:
– Excretory systems in flatworms, earthworms and
vertebrates.
– Osmoregulation in bacteria, fish and protists.
– Osmoregulation in aquatic and terrestrial plants.
– Circulatory systems in fish, amphibians and mammals.
– Thermoregulation in aquatic and terrestrial animals
(countercurrent exchange mechanisms).
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Excretory Systems in Flatworms, Earthworms and Vertebrates
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Nucleus
of cap cell
Cilia
Interstitial fluid
filters through
membrane where
cap cell and tubule
cell interdigitate
(interlock)
Tubule cell
Flame
bulb
Nephridiopore
in body wall
Tubule
Protonephridia
(tubules)
Protonephridia: Flame-Bulb Systems in Flatworms
• The protonephridia of flatworms form a network of dead-end tubules connected to external openings. These tubules branch throughout the body.
• Specialized cells called flame bulbs containing cilia cap the branches of each protonephridium.
• During filtration, beating of the cilia draws water and solutes from the interstitial fluid through the flame bulb, releasing filtrate into the tubule network.
• The urine excreted by freshwater flatworms has a low solute concentration, helping to balance osmotic uptake of water from the environment.
Figure 44.10
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Metanephridia in Earthworms
• Most annelids have metanephridia,
excretory organs that open internally
to the coelom and are enveloped by a
capillary network.
• As the cilia beat, fluid is drawn into a
collecting tubule, which includes a
storage bladder that opens to the outside.
• The metanephridia of an earthworm have
both excretory and osmoregulatory
functions.
• Earthworms inhabit damp soil and
usually experience a net uptake of
water by osmosis through their skin.
• Their metanephridia balance the water
influx by producing urine that is dilute
(hypoosmotic to body fluids).
Figure 44.11
Nephrostome Metanephridia
Nephridio-
pore
Collecting
tubule
Bladder
Capillary
network
Coelom
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Vertebrate Kidneys
• Kidneys are the excretory organs of vertebrates –
they function in both excretion and
osmoregulation.
• Nephrons and associated blood vessels are the
functional unit of the mammalian kidney.
• The mammalian excretory system centers on
paired kidneys which are also the principal site of
water balance and salt regulation.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Proximal tubule
Filtrate
H2O
Salts (NaCl and others)
HCO3–
H+
Urea
Glucose; amino acids
Some drugs
Key
Active transport
Passive transport
CORTEX
OUTER
MEDULLA
INNER
MEDULLA
Descending limb
of loop of
Henle
Thick segment
of ascending
limb
Thin segment
of ascending
limb
Collecting
duct
NaCl
NaCl
NaCl
Distal tubule
NaCl Nutrients
Urea
H2O
NaCl
H2O H2O HCO3
K+
H+ NH3
HCO3
K+ H+
H2O
1 4
3 2
3 5
From Blood Filtrate to Urine: A Closer Look
• Filtrate becomes urine as it flows through the mammalian nephron and
collecting duct – there are 5 main steps in the transformation of blood filtrate to
urine.
Figure 44.14
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Adaptations of the Vertebrate Kidney to Diverse Environments
• Vertebrate animals occupy a wide variety of habitats, and variations in
nephron structure and function equip the kidneys of different
vertebrates for osmoregulation in their various habitats.
– Desert Mammals: nephron structure allows them to rid the body
of slats and nitrogenous wastes without squandering water
(secrete hyperosmotic/highly concentrated urine).
– Aquatic Mammals: have a much lower ability to concentrate
urine because dehydration is not a challenge.
– Birds & Reptiles: nephrons specialized for conserving water so
urine is generally highly concentrated.
– Freshwater Fishes/Amphibians: secrete large amounts of very
dilute urine to excrete excess water continuously.
– Marine Fishes: filtration rates are low and very little urine is
excreted.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Circulatory Systems in Fish, Amphibians and Mammals
FISHES AMPHIBIANS REPTILES (EXCEPT BIRDS) MAMMALS AND BIRDS
Systemic capillaries Systemic capillaries Systemic capillaries Systemic capillaries
Lung capillaries Lung capillaries Lung and skin capillaries Gill capillaries
Right Left Right Left Right Left
Systemic
circuit Systemic
circuit
Pulmocutaneous
circuit
Pulmonary
circuit Pulmonary
circuit
Systemic
circulation Vein
Atrium (A)
Heart:
ventricle (V)
Artery Gill
circulation
A
V V V V V
A A A A A Left
Systemic
aorta
Right
systemic
aorta
Figure 42.4
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Thermoregulation in Aquatic & Terrestrial Animals
• Thermoregulation is the process by which animals
maintain an internal temperature within a tolerable
range.
• Each animal species has an optimal temperature
range, and thermoregulation helps keep body
temperature within that optimal range.
– Endotherms: warmed mostly by heat
generated by metabolism.
– Ectotherms: gain most of their heat from
external sources.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Variation in Body Temperature
• Animals can have either a variable or a constant
body temperature.
– Poikilotherm: an animal whose body
temperature varies with its environment.
– Homeotherm: an animal with a relatively
constant body temperature.
– Note: the terms “cold-blooded” and “warm-
blooded” are misleading and have been
dropped from the scientific vocabulary!
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Balancing Heat Loss and Gain
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Balancing Heat Loss & Gain
• Integumentary System: skin, hair, and nails all provide
mechanisms to prevent heat loss and/or gain.
• Insulation: reduces flow of heat between animals and
their environment.
• Evaporative Heat Loss: water absorbs considerable
heat when it evaporates; this heat is carried away from
the body surface with the water vapor.
• Behavioral Responses: sun basking, huddling, fanning
wings, etc.
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Countercurrent Heat Exchangers
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Control of Body Temperature – Negative Feedback
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
PowerPoint® Lecture Presentations for
Biology
Eighth Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp
BIG IDEA II Biological systems utilize free energy and molecular building blocks
to grow, to reproduce and to maintain dynamic homeostasis.
Enduring Understanding 2.D
Growth and dynamic homeostasis of a biological system
are influenced by changes in the system’s environment.
Essential Knowledge 2.D.3
Biological systems are affected by
disruptions to their dynamic homeostasis.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Essential Knowledge 2.D.3: Biological systems are affected by disruptions to their dynamic homeostasis.
• Learning Objectives:
– (2.28) The student is able to use representations
or models to analyze quantitatively and
qualitatively the effects of disruptions to dynamic
homeostasis in biological systems.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Disruptions at the molecular and cellular levels affect the health of the organism.
• Illustrative Example: dehydration/desiccation.
– Dehydration is the excessive loss of body water, with an accompanying disruption
of metabolic processes. Extreme dehydration, or desiccation, is fatal for most
animals.
– Symptoms may include headaches, decreased blood pressure, and dizziness or
fainting when standing up due to orthostatic hypotension. Untreated dehydration
generally results in delirium, unconsciousness, swelling of the tongue and, in
extreme cases, death.
– The symptoms become increasingly severe with greater water loss. One's heart
and respiration rates begin to increase to compensate for decreased plasma
volume and blood pressure, while body temperature may rise because of
decreased sweating.
– At around 5% to 6% water loss, one may become groggy or sleepy, experience
headaches or nausea, and may feel tingling in one's limbs.
– With 10% to 15% fluid loss, muscles may become spastic, skin may shrivel and
wrinkle (decreased skin turgor), vision may dim, urination will be greatly reduced
and may become painful, and delirium may begin. Losses greater than 15% are
usually fatal.
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Disruptions to ecosystems impact the dynamic homeostasis or balance of the ecosystem.
• Illustrative Example: invasive species.
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Disruptions to ecosystems impact the dynamic homeostasis or balance of the ecosystem.
• Illustrative Example: human impact.
– As the human population has grown, our activities
have disrupted the trophic structure, energy flow, and
chemical cycling of many ecosystems.
– In addition to transporting nutrients from one location
to another, humans have added new materials, some
of them toxins, to ecosystems.
– Disruptions that deplete nutrients in one area and
increase them in other areas can be detrimental to
ecosystem dynamics.
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Fig. 55-17: Agriculture & Nitrogen Cycling
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Fig. 55-18 – Contamination of Aquatic Ecosystems
Winter Summer
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Acid Precipitation
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Toxins in the Environment
• Humans release many toxic chemicals, including synthetics previously unknown to nature
• In some cases, harmful substances persist for long periods in an ecosystem
• One reason toxins are harmful is that they become more concentrated in successive trophic levels
• Biological magnification concentrates toxins at higher trophic levels, where biomass is lower
Fig. 55-20
Lake trout 4.83 ppm
Herring gull eggs 124 ppm
Smelt 1.04 ppm
Phytoplankton 0.025 ppm
Zooplankton 0.123 ppm
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Greenhouse Gases and Global Warming
Ozo
ne layer
thic
kn
ess (
Do
bso
ns)
Fig. 55-23
Year
’05 2000 ’95 ’90 ’85 ’80 ’75 ’70 ’65 ’60 1955 0
100
250
200
300
350
Fig. 55-24
O2
Sunlight
Cl2O2
Chlorine
Chlorine atom
O3
O2
ClO
ClO
Fig. 55-25
(a) September 1979 (b) September 2006
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
PowerPoint® Lecture Presentations for
Biology
Eighth Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp
BIG IDEA II Biological systems utilize free energy and molecular building blocks
to grow, to reproduce and to maintain dynamic homeostasis.
Enduring Understanding 2.D
Growth and dynamic homeostasis of a biological system
are influenced by changes in the system’s environment.
Essential Knowledge 2.D.4
Plants and animals have a variety of chemical defenses
against infections that affect dynamic homeostasis.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Essential Knowledge 2.D.4: Plants and animals have a variety
of chemical defenses against infections that affect dynamic homeostasis.
• Learning Objectives:
– (2.29) The student can create representations
and models to describe immune responses.
– (2.30) The student can create representations or
models to describe nonspecific immune defenses
in plants and animals.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Plants, invertebrates and vertebrates have multiple, nonspecific immune responses.
• A nonspecific immune response is a nonspecific
prevention of the entrance of invaders to the body.
– Plant defenses against pathogens include molecular
recognition systems with systemic responses; infection
triggers chemical responses that destroy infected and adjacent
cells, thus localizing the effects.
– Invertebrate immune systems have nonspecific response
mechanisms, but the lack pathogen-specific defense responses.
– Vertebrate immune systems have nonspecific and
nonheritable defense mechanisms against pathogens, but they
also have specific immune responses.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Chemical Defenses in Plants
• Plants have a variety of chemical defenses against infections
that affect dynamic homeostasis – these are examples of
nonspecific immune responses.
– Plant defenses against pathogens include molecular recognition
systems with systemic responses;
– Infection triggers chemical responses that destroy infected and
adjacent cells, thus localizing the effects.
• Chemical defenses in plant cells are an illustration of how cells
communicate with each other through direct contact with other
cells (via plasmodesmata).
• In plants, cells communicate over short distances by using local
regulators (chemicals) that target cells in the vicinity of the
emitting cell.
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Defense Response Against Pathogen in Plants
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Plant Defenses Against Herbivores
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Innate/Nonspecific Immunity of Invertebrates
• In insects, an exoskeleton made of chitin forms
the first barrier to pathogens.
• The digestive system is protected by low pH
and lysozyme, an enzyme that digests
microbial cell walls.
• Hemocytes (special cells) circulate within
hemolymph (insect blood-like substance) and
carry out phagocytosis, the ingestion and
digestion of foreign substances including
bacteria.
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Phagocytosis by an Invertebrate Hemocytic Cell
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Mammals use specific immune responses triggered by natural or artificial agents that disrupt homeostasis.
• Animals are constantly under attack by pathogens,
infectious agents that cause disease.
• Dedicated immune cells patrol the body fluids,
searching out and destroying foreign cells. These
defenses make up an immune system.
• Most animal immune systems use receptors that
specifically bind molecules from foreign cells or
viruses (cellular communication).
• There are two general strategies for such molecular
recognition: innate immunity and acquired
immunity.
Fig. 43-2
INNATE IMMUNITY
Recognition of traits shared by broad ranges of pathogens, using a small set of receptors
•
• Rapid response
• Recognition of traits specific to particular pathogens, using a vast array of receptors
• Slower response
ACQUIRED IMMUNITY
Pathogens (microorganisms
and viruses)
Barrier defenses: Skin Mucous membranes Secretions
Internal defenses: Phagocytic cells Antimicrobial proteins Inflammatory response Natural killer cells
Humoral response: Antibodies defend against infection in body fluids.
Cell-mediated response: Cytotoxic lymphocytes defend against infection in body cells.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Innate/Nonspecific Immunity: Barrier Defenses
• Barrier defenses include the skin and mucous
membranes of the respiratory, urinary, and
reproductive tracts:
– Mucus traps and allows for the removal of
microbes.
– Many body fluids including saliva, mucus, and
tears are hostile to microbes because they
contain lysozyme.
– The low pH of skin and the digestive system
prevents growth of microbes.
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Cellular Innate Defenses
• Cellular innate defenses combat pathogens that get through the skin.
They include phagocytic white blood cells and antimicrobial proteins.
– The nonspecific cellular defense of vertebrates is headed up by cells
called phagocytes. Macrophages and neutrophils roam the body in
search of bacteria and dead cells to engulf and clear away.
– Phagocytic WBCs recognize microbes using toll-like receptors (TLRs).
– They recognize fragments of molecules characteristic of a particular type
of pathogen…this helps to increase the efficiency of phagocytosis.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cellular Innate Defenses & Phagocytosis
• Phagocytic cells get some assistance in recognizing
foreign invaders by a protein molecule called
complement.
• About 30 proteins make up the complement system.
• These proteins makes sure that molecules to be cleared
have some sort of identification displaying the need for
phagocyte assistance.
• Complement coats these cells, stimulating phagocytes to
ingest them.
• This is a part of the non-specific immune defense because
the phagocytes are no seeking particular invaders.
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Antimicrobial Peptides and Proteins
• Peptides and proteins function in innate defense by attacking microbes directly
or impeding their reproduction.
• For example, interferon proteins provide innate defense against viruses and
help activate macrophages. It does so by causing cells adjacent to an infected
cell to produce substances that inhibit viral replication.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 43-8-3
Pathogen Splinter
Macrophage
Mast cell
Chemical signals
Capillary
Phagocytic cell Red blood cells
Fluid
Phagocytosis
In local inflammation, histamine and other chemicals released from
injured cells promote changes in blood vessels that allow more fluid, more
phagocytes, and antimicrobial proteins to enter the tissues.
Inflammatory Responses http://www.sumanasinc.com/webcontent/animations/content/inflammatory.html
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Natural Killer Cells & MHC
• Ever wonder how phagocytes and other cells of the immune system avoid
killing all cells?
• All cells in the body (except red blood cells) have a class 1 MHC protein
on their surface.
• MHC molecules are normal cell-surface proteins that are encoded by a family
of genes called the major histocompatibility complex.
• These are a group of genes that slightly differ from one individual to another –
A MAJOR COMPONENT OF “SELF-RECOGNITION”.
• The immune system accepts as “friendly” any cell that has the identical match
for this molecule. Anything with a different MHC is “foreign”.
– Cancerous or infected cells no longer express this protein; and natural killer (NK)
cells attack these damaged cells:
– NKC’s often trigger apoptosis in the cells they attack.
– Apoptosis is programmed cell death brought about by signals that trigger the
activation of a cascade of “suicide” proteins in the cells destined to die.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Mammals use specific immune responses triggered by natural or artificial agents that disrupt dynamic homeostasis.
• The mammalian immune system includes two
types of specific responses: cell mediated and
humoral.
– In the cell-mediated response, cytotoxic T
cells, a type of lymphocytic white blood cell,
“target” intracellular pathogens when antigens
are displayed on the outside of the cells.
– In the humoral response, B cells, a type of
lymphocytic white blood cell, produce
antibodies against specific extracellular
antigens.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
B cells and T cells provide pathogen-specific recognition in adaptive immunity.
• Vertebrates have two types of lymphocytes: B
cells (proliferate in bone marrow) and T cells
(mature in the thymus).
• These circulate through the blood and both
recognize particular antigens.
– Antigens are foreign molecules that elicit a response
by lymphocytes. B and T cells recognize them by
specific receptors embedded on their plasma
membranes.
– Antibodies are proteins secreted by B cells during an
immune response.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Antigens and Antibodies
• Antibodies are proteins produced by B cells, and
each antibody is specific to a particular antigen.
• Antigens in the body are recognized by antibodies to
the antigen.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Activation of B and T Cells
• B or T cell activation occurs when an antigen
binds to a B or T cell:
– B cell activation is enhanced by cytokines. When
activated, B cells form 2 types of clones: effector cells
(combat the antigen) and memory cells (recognize
antigen in subsequent infections).
– B cell receptors bind to INTACT antigens.
– T cell receptors bind to antigens that are displayed by
antigen-presenting cells on their MHCs.
– Each B or T cell responds to only ONE antigen.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
B Cell Receptors for Antigens
• B cell receptors bind to specific, intact antigens – whether
that antigen is free or on the surface of a pathogen.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
T Cell Receptors for Antigens
V V
C C
• T cells bind to small fragments of antigens presented on
the surface of macrophages.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The TWO Branches of Acquired Immunity
• HUMORAL IMMUNE RESPONSE: involves the
activation and cloning of effector B cells, which
produce antibodies that circulate in the blood.
• CELL-MEDIATED IMMUNE RESPONSE: involves
the activation and clonal selection of cytotoxic T
cells, which identify and destroy infected cells.
• NOTE: Helper T cells aid in BOTH responses –
when activated with the Class II MHC molecules of
an antigen-presenting cell, they secrete cytokines
that stimulate and activate both B cells and
cytotoxic T cells.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Class I and Class II MHC Molecules are Different
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Antigen Presentation by Cells
Participants in the Acquired Immune Response http://bcs.whfreeman.com/thelifewire/content/chp18/1802004.html (humoral response)
http://bcs.whfreeman.com/thelifewire/content/chp18/1802003.html (cell-mediated response)
Figure 43.14
Humoral immune response Cell-mediated immune response
First exposure to antigen
Intact antigens Antigens engulfed and
displayed by dendritic cells
Antigens displayed
by infected cells
Activate Activate Activate
Gives rise to Gives rise to Gives rise to
B cell Helper
T cell Cytotoxic
T cell
Plasma
cells
Memory
B cells
Active and
memory
helper
T cells
Memory
cytotoxic
T cells
Active
cytotoxic
T cells
Secrete antibodies that defend against
pathogens and toxins in extracellular fluid
Defend against infected cells, cancer
cells, and transplanted tissues
Secreted
cytokines
activate
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Helper T Cells: A Response to Nearly All Antigens
Figure 43.15
After a dendritic cell engulfs and degrades a bacterium, it displays
bacterial antigen fragments along with a class II MHC molecule on the cell’s surface. A specific helper T cell binds
to the displayed complex. This interaction promotes secretion of cytokines by the dendritic cell.
Proliferation of the T cell, stimulated
by cytokines from both the dendritic
cell and the T cell itself, gives rise to
a clone of activated helper T cells
(not shown), all with receptors for the
same MHC–antigen complex.
The cells in this clone
secrete other cytokines
that help activate B cells
and cytotoxic T cells.
Cell-mediated
immunity
(attack on
infected cells)
Humoral
immunity
(secretion of
antibodies by
plasma cells)
Dendritic
cell
Dendritic
cell
Bacterium
Peptide antigen
Class II MHC
molecule
TCR
CD4
Helper T cell
Cytokines
Cytotoxic T cell
B cell
1
2 3
1
2 3
B Cells: A Response to Extracellular Pathogens
2
1 3
B cell
Bacterium
Peptide
antigen
Class II
MHC
molecule
TCR
Helper T cell
CD4
Activated
helper T cell Clone of memory
B cells
Cytokines
Clone of plasma cells Secreted antibody
molecules
Endoplasmic
reticulum of
plasma cell
Macrophage
After a macrophage engulfs and degrades
a bacterium, it displays a peptide antigen
complexed with a class II MHC molecule.
A helper T cell that recognizes the displayed
complex is activated with the aid of cytokines
secreted from the macrophage, forming a
clone of activated helper T cells (not shown).
1 A B cell that has taken up and degraded the
same bacterium displays class II MHC–peptide
antigen complexes. An activated helper T cell
bearing receptors specific for the displayed
antigen binds to the B cell. This interaction,
with the aid of cytokines from the T cell,
activates the B cell.
2 The activated B cell proliferates
and differentiates into memory
B cells and antibody-secreting
plasma cells. The secreted
antibodies are specific for the
same bacterial antigen that
initiated the response.
3
Figure 43.17
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cytotoxic T cell
Perforin
Granzymes
CD8 TCR
Class I MHC
molecule
Target
cell Peptide
antigen
Pore
Released
cytotoxic
T cell
Apoptotic
target cell
Cancer
cell
Cytotoxic
T cell
A specific cytotoxic T cell binds to a
class I MHC–antigen complex on a
Target cell. This interaction, along with
cytokines from helper T cells, leads to
the activation of the cytotoxic cell.
1 The activated T cell releases perforin
molecules, which form pores in the
target cell membrane, and other enzymes),
which enter the target cell by endocytosis.
2 The granzymes initiate apoptosis within the
target cells, leading to fragmentation of the
nucleus, release of small apoptotic bodies,
and eventual cell death. The released
cytotoxic T cell can attack other target cells.
3
1
2
3
Figure 43.16
Cytotoxic T Cells: A Response to Infected Cells and Cancer Cells
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Primary and Secondary Immune Response http://www.professorcrista.com/files/animations/posted_animations/humoral_secondary.html
Antibody c
oncentr
ation
(arb
itra
ry u
nits)
104
103
102
101
100
0 7 14 21 28 35 42 49 56
Time (days) Figure 43.13
Antibodies
to A Antibodies
to B
Primary
response to
antigen A
produces anti-
bodies to A
2 Day 1: First
exposure to
antigen A
1 Day 28:
Second exposure
to antigen A; first
exposure to
antigen B
3 Secondary response to anti-
gen A produces antibodies
to A; primary response to anti-
gen B produces antibodies to B
4
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