Download Search for Better Health Syllabus Notes

9.4 SEARCH FOR BETTER HEALTH
1. What is a healthy organism?
What is meant by the term disease?
Background: Disease is any condition that adversely affects the function of any part of a living thing. Health
is the wellbeing of the organism. All our body functions, which are under the control of our genes, work
together to maintain health.
Discuss the difficulties of defining the terms 'health' and 'disease'
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The definition of disease above is very broad. Disease can cover a wide range of conditions that fit
the above definition including minor conditions, such as a cut finger or an ant bite, as well as the
more obvious diseases.
Health varies on a daily basis and is not just the absence of disease. Health varies with age and the
susceptibility to disease. It is a state of physical, mental and social wellbeing.
The difficulties of defining the terms health and disease include that:
o it is possible for a person to be healthy and have a disease at the same time
o the terms are used in general conversation and have different meaning to the scientific
definition.
Use available evidence to analyse the links between gene expression and maintenance and repair of
body tissue
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Gene expression refers to the transfer of information from a gene to produce a protein or RNA. If
you cut yourself, the genetic code contained in all your cells is used to form the new tissue to repair
the damage from the cut.
Analyse the information by identifying cause and effect relationships between gene expression and
the maintenance and repair of body tissue.
Consider, that if a certain gene expresses, what the effect will be on:
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regulation of the cell cycle
mitosis
protein synthesis.
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Use the information you have gathered to synthesise an account of the connection between gene
expression and the maintenance of healthy tissue.
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Outline how the function of genes, mitosis, cell differentiation and specialisation assist in the
maintenance of health
Gene expression is essential for the maintenance of health.
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Genes are the units of inheritance. They control the process of protein synthesis. They assist the
maintenance of health by regulating the cell cycle and limiting the growth and reproduction of cells.
Genes provide the code for proteins that are needed for growth and repair. Enzymes, which control
all body processes, are proteins and thus have been produced from the codes of genes.
Mitosis is cell division that produces identical cells. These cells are important for growth and
reproduction. Each day millions of cells die and are replaced by the process of mitosis.
Cell differentiation is the process undergone by the cells that are formed after mitosis. Each cell has
the genetic information necessary to produce all types of cells. However, each cell normally
differentiates to become a specialised cell, with a specialised structure and function.
Undifferentiated cells form tumours.
Many types of cells have specialised roles in maintaining the health of an organism. For example,
there are specialised blood cells that produce antibodies to attack a disease causing microorganism.
2. Infectious and non-infectious diseases
2. Over 3000 years ago the Chinese and Hebrews were advocating cleanliness in food, water and
personal hygiene
Background: Even though they did not know about microscopic disease-causing organisms, many social
groups established rules and practices that protected people against infectious diseases. These practices
resulted from observing cause and effect relationships. For example, the Chinese could have deduced the
connection between water contaminated by faeces and gastro-intestinal diseases, and the Hebrews may
well have made a connection between the symptoms of infection by tapeworms and eating undercooked
pork.
Distinguish between infectious and non-infectious disease
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An infectious disease is one that is caused by an organism and that can be transferred from one
person to another. The transfer may be direct, where the disease-causing organisms, such as
viruses or bacteria, pass directly from person to person, or it may be carried out by an intermediary
(called a vector), such as a blood-sucking insect. Examples of infectious diseases are colds, influenza,
chicken pox, herpes and measles.
Non-infectious diseases are diseases that are not due to disease-causing organisms. They include
genetic diseases, such as Down syndrome, haemophilia, and those that are related to lifestyle or
environment, such as cardiovascular disease and skin cancer.
Identify data sources, plan and choose equipment or resources to perform a first hand investigation to
identify microbes in food or in water
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Agar is a jelly-like substance obtained from seaweed. When it is dissolved in water, nutrients
suitable for microbes can be added to it before it sets to form a gel. If a microbe makes contact with
the agar and if conditions are suitable, the microbe will grow and reproduce to form a visible
colony.
To design a first-hand investigation to identify microbes in food and water, firstly identify data
about microbiological techniques from practical manuals or the Internet. Gather information about
the techniques used to grow micro-organisms on agar plates in Petri dishes. You will need to know
what sort of nutrients can be added to agar, the correct way of exposing the agar to the source of
micro-organisms and the safety precautions that must be followed once a plate has been exposed.
Also you will need to know the best temperature for microbial growth and how to distinguish
between colonies of bacteria and fungi, growing on agar plates.
Use the information to plan a valid and reliable investigation. You will need to decide on which
nutrients you will add to the agar, what food and water samples you will test and how you will
expose the agar to the microbes that may be present in your food and water samples. Decide on
the temperature you will provide for microbial growth.
Choose equipment and resources that will ensure your investigation is safe. Carry out a risk
assessment of your experimental procedures and address potential hazards. In this type of
investigation, the most important safety procedures are:
o to seal and not open again the Petri dishes after exposure
o to correctly autoclave exposed Petri dishes prior to final disposal.
Perform your investigation. Dispose carefully and safely of the waste materials produced during the
investigation. Safe working practices such as wearing latex gloves, washing benches and hands with
chemical treatments for sterilisation are important when working with micro-organisms.
Use data from the investigation to explain why cleanliness in food, water and personal hygiene
practices are important.
Explain why cleanliness in food, water and personal hygiene practices assist in the control of disease
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There are huge numbers of disease causing organisms. Most of them are microscopic and can enter
the body through any body opening. The intake of food and water provide an easy way for microorganisms to enter our bodies. Therefore, minimising the number of such organisms in our food and
water reduces the risk of infection. Good personal hygiene ensures that body openings, including
broken skin, are clean, so that the number of micro-organisms that might gain entry to our bodies is
kept low. Since we cannot see individual micro-organisms we take precautions that we know will
help to protect us. Examples of precautions include, washing hands after going to the toilet,
cleaning wounds, boiling water and water treatment of water that doesn't come from a known safe
source to make sure untreated sewage does not get into food or water supplies.
Identify the conditions under which an organism is described as a pathogen
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A pathogen is any organism that can produce a disease. Pathogens range from viruses so small that
thousands will fit side by side in one millimetre to tapeworms that can be several metres long. They
are all infectious.
Pathogens may live outside the body, such as the fungus that causes ringworm, inside particular
organs, such as parasitic worms in the intestine, in tissues or inside cells. Some information on
water pathogens is found below.
Gather, process and analyse information from secondary sources to describe ways in which drinking
water can be treated and use available evidence to explain how these methods reduce the risk of
infection from pathogens
Contamination of drinking water is a common way for pathogens to enter the body.
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Gather information from your local water supply authority or the Internet to find out the ways in
which water can be treated and the range of pathogens that are targeted.
Process your information by recording a description of each water treatment method and by
looking for trends and patterns in why they are used.
Information to get you started
Examples of water treatments are filtration, chlorination and ozone filtration. In NSW water is
filtered, chlorine is added to kill bacteria and samples are tested for the presence of coliform
bacteria, giardia and cryptosporidium.
Use questions as an effective processing technique to focus your attention when looking for trends
in information sources. Some examples in this case might be “Which microbes are controlled by the
treatment?”, “Which microbes are not controlled by the treatment?” and “What combination of
treatments can be used to make a water supply safe for drinking?”
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Use the evidence you have gathered to propose logical explanations of how each form of water
treatment protects people from the target pathogens.
3. Identifying microbes that cause disease
3. During the second half of the nineteenth century, the work of Pasteur and Koch and other scientists
stimulated the search for microbes as causes of disease
Background: Microbes as the cause of infectious disease:
 Until mid 19th century, spontaneous generation believed origin of living things.
 Derived from non-living matter.
 680, Francesco Redi disproved spontaneous generation.
 Scientists refused to accept his results.
 Belief of spontaneous generation remained.
 Prevented people understanding causes of disease & transmission.
Describe the contribution of Pasteur and Koch to our understanding of infectious diseases
Louis Pasteur
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The role of Pasteur in identifying the causes of disease was:
o that he disproved the theory of spontaneous generation, which was widely held at the time.
Before Pasteur's work, people believed that maggots and fungi grew naturally from nonliving material
o that he showed that micro-organisms came from pre-existing micro-organisms.
o Discovered germ theory of disease:
o Most infectious diseases caused by micro-organisms or germs.
o Examined fermented wines under microscope.
o Described micro-organisms growing.
o Demonstrations of living organisms existing in air destroy theory of spontaneous generation.
o Showed French wine industry that heating wine to 55 oC destroyed microorganisms.
o Pasteurisation - Now applied to:
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Beer;
Milk.
o Founded vaccination.
 Inoculated 25 sheep with weakened Bacillus anthracis (anthrax bacteria);
 Injected 50 sheep with strong dose of anthrax;
 Predicted 25 would die;
 25 inoculated sheep survived.
 Developed vaccination for – Anthrax, Chicken cholera, Swine erysipelas.
 Developed rabies vaccination in 1885, saved life of infected boy.
Robert Koch
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About 150 years ago, Pasteur's work in identifying, under the microscope, the organism that caused
fermentation, led some people to suggest the infectious diseases were caused by microscopic
pathogens. Others argued that bacteria found in sick animals followed the infection, rather than
causing it.
The work of Robert Koch (1843 - 1910) provided the proof that was needed to convince people that
microscopic pathogens cause disease. His first experiments were with the disease anthrax in sheep.
Later, he obtained similar results for tuberculosis and cholera.
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First Koch found bacteria in sheep infected with anthrax. Then, he placed the bacteria on agar
plates in Petri dishes so that many colonies of the bacteria were produced. He used bacteria from
these colonies to infect healthy sheep and found that they became infected.
After his experiments with anthrax, Koch was able to state a series of steps that are needed to
identify the micro-organism responsible for a particular disease. These steps are called Koch's
postulates.
o Step 1: All infected hosts must contain the suspect organism.
o Step 2: A pure culture of the suspect organism must be obtained.
o Step 3: A healthy organism infected with the pure culture must have the same symptoms as
the original host.
o Step 4: The suspect organism must be isolated from the second host, grown in pure culture
and prove to be identical to the first culture.
Koch's postulates can be used to identify the causative organism of an infectious disease. The
symptoms of the disease are carefully identified and then the blood of sufferers is examined to
determine possible causative organisms. A particular micro-organism will be suspected if other
sufferers have the same micro-organism present in their blood and a mechanism can be identified
to allow transfer of the micro-organism. Identification of the organism in more sufferers will
confirm the causative organism. Sometimes, a suspected causative organism can be confirmed by
infecting a test organism.
Perform an investigation to model Pasteur's experiment to identify the role of microbes in decay
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Perform Pasteur's experiment that showed that something from the air causes meat broth to go
bad. As you conduct your experiment consider which variables need to be kept constant and be
able to explain which are the dependent and which are independent variables.
Procedure:
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1. Use a meat extract cube to make a clear broth.
2. Use two conical flasks instead of Pasteur's balloon flasks. Fit the flasks with one-holed
stoppers. Use glass tubing bent into an S-shape to replace Pasteur's swan-necked flask. Place
a straight piece of glass tubing in the other flask.
3. Put some broth into both flasks and boil gently for fifteen minutes.
4. Leave both flasks, not in direct sunlight for several weeks. Every two or three days compare
the contents of the two flasks. Look for cloudiness, scum, bubbles and mould colonies.
Record your results.
Assess the accuracy of your observation and the relative importance of the data gathered. You
could do this by comparing your experiment with the description of Pasteur's experiment, which
follows.
Pasteur's experiment
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When Pasteur did his experiment, the broth in the swan-necked flask remained clear for several
weeks, while that in the open flask quickly became cloudy and smelly.
Both flasks were open to the air. In the swan-necked flask, air could move freely through the neck
of the flask just as it did in the straight-necked flask, but the much heavier micro-organisms, in the
air, were trapped in the bottom part of the S-curve.
This experiment showed that for the broth to grow micro-organisms and start to decay, there had
to be access to air containing the spores of micro-organisms.
Gather and process information to trace the historical development of our understanding of the cause
and prevention of malaria
Background on malaria
Malaria is a disease caused by a protozoan of the genus Plasmodium. It has a complicated life cycle
requiring a mosquito of the Anopheles genus to carry the Plasmodium to its host. The disease is common in
tropical areas where the Anopheles mosquito lives. The female mosquito requires a blood meal to
complete the reproduction cycle of the mosquito. During the blood meal the Plasmodium (sporozoites) are
transferred from the mosquito salivary glands into the blood system of the host. The sporozoites travel to
the liver via the blood system and enter cells in the liver. After 12 days a new form of the protozoan called
merozoites are released and these enter blood cells. At the same time toxins are released. This causes the
sweats and fever that are associated with the disease. Some of the merozoites develop into gametocytes
and may be sucked up by another mosquito in another blood meal. In the gut of the female mosquito the
gametocytes become gametes and are fertilised. This forms sporozoites which will travel to the salivary
glands of the female mosquito and await the next blood meal to enter another host.
The disease was known from the start of recorded history but it took many researchers to uncover the
complicated life cycle above. Sir Ronald Ross (1857 - 1932) was a British medical officer working in India.
For thousands of years, people had been puzzled about the way in which malaria spread but they knew
that malaria was common in areas close to swampy land. In the late 1800s, people were beginning to
wonder if mosquitoes could spread malaria. Ross collected mosquitoes and painstakingly dissected them
under a microscope. He discovered the micro-organism that was known to cause malaria, inside the bodies
of Anopheles mosquitoes. This led to the realisation that insects could carry pathogens, that is, they can be
vectors of disease.
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Use reference books or the Internet to gather information to trace how scientists identified the
cause and prevention of malaria.
Process this information to show how their work contributed to our understanding of the cause and
prevention of malaria. Trends and patterns could be well illustrated through the use of an
annotated timeline. The table below is a guideline.
Date
Development
18 BC
The disease malaria was described by the Romans. Malaria was thought to come from
swamps so the name means 'bad air'
1820
Quinine used to prevent the disease
1880
Charles Laveran a French army doctor observed the malarial parasite
1886
Golgi observed asexual reproduction in the protozoan Plasmodium and identified two
species
1898
Giovanni Grassi named the Anopheles mosquito as the carrier of the malarial parasite
1897
Ronald Ross discovered that Plasmodium was the protozoan that caused the disease
malaria.
1940
Chloroquinine the first synthetic anti-malarial drug was used
Distinguish between:
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prions
viruses
bacteria
protozoans
fungi
macro-parasites
and name one example of a disease caused by each type of pathogen
Pathogen
Description
Examples of diseases it causes
Protein that has been altered from its normal
structure and can then alter other proteins to
develop more prions, so that the change
spreads like a chain reaction.
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scrapie in sheep
spongiform encephelopathy in cattle (mad cow
disease)
Creutzfeldt-Jakob (CJD) disease in humans
Viruses
Consist of DNA or RNA enclosed in protein,
live inside living cells. They are so small that
they cannot be seen with a light microscope.
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influenza
measles
a common cold
herpes
AIDS
Warts
Hepatitis
Foot-and-mouth disease
Plum pox virus
Bacteria
Very simple cells with no internal
membranes.
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Boils
Cholera
Legionnaire's disease
Tuberculosis
Crown gall blight
Protozoans
Microscopic single-celled organisms with
internal membranes.
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Amoebic dysentery
Giardia,
Malaria,
Fungi
Heterotrophic organisms. Some (e.g. yeasts)
are unicellular, others consist of long
branching threads.
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Ringworm
Tinea
Thrush
Many plant diseases such as damping off in
seedlings
Macroorganisms
Organisms that are visible to the naked eye,
also called parasites.
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fleas
ticks
tapeworms
bilharzia worms
hydatid worms
liver fluke
many plant parasites, e.g. aphids
Prions
Identify the role of antibiotics in the management of infectious disease
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Antibiotics play an important role in the management of infectious diseases. Antibiotics were
discovered by Alexander Fleming in 1928. They are naturally occurring compounds produced by one
organism to prevent the growth of bacteria. Before the discovery of antibiotics, many people died
of what we now would think of as simple infections.
Process information from secondary sources to discuss problems relating to antibiotic resistance
Background
Unfortunately, the overuse of antibiotics has led to the selection of more virulent bacteria that are
resistant to antibiotics.
When antibiotics were first introduced, they had a dramatic effect on the pathogens that cause disease.
Over time, it became apparent that the effects of the antibiotics were beginning to become less potent.
This was because of the development of drug resistance in the pathogen. Each time an antibiotic is used,
there may be some individual pathogens that have a natural resistance to the drug. These naturally
resistant individuals are left to breed the next generation and pass on the genetic information that made
them resistant. The next time the drug is used, it will have no effect. Overuse of antibiotics has resulted in
"superbugs". These strains are resistant to antibiotics and include vancomycin resistant golden staph
(Staphylococcus aureus). These organisms are not destroyed by our strongest antibiotics. Scientists are
developing new antibiotics such as Zyvox to deal with multi-resistant bacteria. In the future, unless new
antibiotics are produced, common infections will once again be responsible for many deaths.
Many household products and cleaning agents now contain antibiotics. These do not kill all bacteria so act
as a selecting agent for antibiotic resistant bacteria. These can increase in number without competing with
other bacteria.
The use of antibiotics in farm animals also has the same effect of selecting for antibiotic resistant bacteria.
Some farm industries put human antibiotics into the feed of their animals, thus increasing the build up of
antibiotic resistant bacteria. During the production of meat, animals are given antibiotics to prevent
infections. When the meat reaches the table, it may still contain these animal antibiotics. This could lead to
more antibiotic resistant bacteria.
It is important to complete a course of antibiotics even when the symptoms are gone. This will ensure that
the bacteria have been completely destroyed. Not finishing antibiotics can lead to the selection of
antibiotic resistant strains.
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Process this information to discuss the problems of antibiotic resistance. Trends and patterns could
be illustrated by the unending cycle between the introduction of new antibiotics and the
development of resistance in bacteria.
Identify data sources, gather, process and analyse information from secondary sources to describe one
named infectious disease in terms of its:
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cause
transmission
host response
major symptoms
treatment
prevention
control
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To address this dot point, it is a good idea to select an infectious disease that interests you or that
represents a significant problem in your community.
Use the list presented in the dot point to determine the type of information that you need to
collect. Gather the information from a range of sources including digital technologies, locally
available health brochures or pamphlets and the Internet. Process the accuracy of the information
by looking for information that is consistently represented across a range of reputable publications.
Analyse your information by developing accurate generalisations into short notes.
A good example of a named infectious disease is malaria. The following is a description of the disease.
Factors
Description
Cause
The parasitic protozoan, Plasmodium
Transmission
Anopheles mosquito is the insect vector. Blood from a malaria victim contains Plasmodium
sex cells. These form zygotes in cysts in the stomach wall of the mosquito and mature into
sporozoites. When a cyst bursts, the sporozoites travel to the mosquito salivary glands, from
where they are transferred to the victim of the mosquito bite. The sporozoites travel to the
liver, multiply and then enter the red blood cells, where they also multiply. When the
infected cells burst, they cause the malarial fever. Male and female gametes are produced
from these sporozoites, which are then taken in the blood the next time a mosquito bites.
Host response
When in the blood cells the host produces antibodies against Plasmodium
Major symptoms
Chills, fever, sweating, delirium and headache
Treatment
Anti-malarial drugs such as quinine and chloroquinine
Prevention
Cover up after dark and use personal insecticide, mosquito nets
Control
Draining swamps, spraying with insecticides.
4. Defence against disease
4. Often we recognise an infection by the symptoms it causes. The immune response is not so obvious,
until we recover
Background: Our bodies have three types of defence against pathogens. The first consists of several
barriers that prevent the entry of micro-organisms. The second is the action of white blood cells in
destroying foreign particles, in a process called phagocytosis. The third is carried out by the immune
system, which plays a complex role in targeting and destroying pathogens as well as helping to make our
bodies resistant to them.
Our bodies contain very large numbers of bacteria (15% of your body weight) and many of those in the
intestine are essential for our wellbeing. The collective term for all the micro-organisms in our bodies, both
the beneficial and harmless ones, is microflora. An imbalance of microflora in the gut can lead to disease
symptoms such as diarrhoea and malabsorption of nutrients.
Gather, process and present information from secondary sources to show how a named disease results
from an imbalance of microflora in humans.
Background: Pathogenic microflora usually attack specific parts of the body. For example, the protozoan
that causes malaria lives in red blood cells, the bacterium that causes cholera lives in the intestine, the
bacterium that causes trachoma lives in the eyes, one type of the Herpes virus is active in cells around the
lips and nose (causing cold sores) and another type is active in cells in the genital area (genital herpes).
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Choose a disease that results from an imbalance of microflora in humans, such as Crohn's disease or
candida (thrush). Use biology textbooks, library references and, if possible, the Internet to gather
information about the cause, symptoms and effects of the disease.
To process the sources you find, assess their reliability by comparing the information provided.
Look for consistency of information.
It is appropriate for this syllabus point that you present your findings as a report. A scaffold and
some language features of a report follow:
Scaffold for a report
Classification
Description
Features
Classify the disease. Briefly preview the features to be described. Use
generalised terms. Use linking verbs like is, has, becomes. Use present
tense.
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Focus on a specific feature for each paragraph. Begin each
paragraph with a topic sentence.
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Use present tense.
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Use action verbs, such as occurs, called, makes.
(Feature 1: e.g. cause)
(Feature 2: e.g. symptoms)
(Feature 3: e.g. effects)
Identify defence barriers to prevent entry of pathogens in humans:
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skin
mucous membrane
cilia
chemical barriers
other body secretions
Line of defence
Description
What it does
skin
Skin continuously grows by new cells being
produced from below. Cells fit tightly
together to form a protective layer
covered by dead cells.
When unbroken, skin prevents the entry
of pathogens. Pores in the skin secrete
substances that kill bacteria.
mucous membrane
cells lining the respiratory tract and
openings of the urinary and reproductive
systems that secrete a protective layer of
mucus
Mucus is sticky and traps pathogens and
other particles. When there are many
pathogens more mucus is produced to
flush them out.
cilia
Hair-like projections from cells lining the
air passages
Move with a wavelike motion to push
pathogens from the lungs up to the
throat.
chemical barriers
acid in the stomach; alkali in the small
intestine; the enzyme, lysozyme, in tears
Stomach acid destroys pathogens,
including those that are carried to the
throat by cilia and then swallowed. Alkali
destroys acid resistant pathogens.
Lysozyme dissolves the cell membranes of
bacteria.
Other body secretions
secretions from sweat glands and oily
secretions from glands in hair follicles
Contain chemicals that destroy bacteria
and fungi.
Identify defence adaptations, including:
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inflammation response
phagocytosis
lymph system
cell death to seal off pathogen
inflammation response
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Inflammation occurs when blood vessels around an infected area are supplied with extra blood.
This makes the area swollen and red. The release of histamines by the damaged tissue increases the
permeability of the blood vessels, which allows white blood cells to leave the blood vessels and
move into the damaged tissue.
phagocytosis
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Some white blood cells, called macrophages and neutrophils, can very easily change their shape so
that they flow around particles and completely enclose them within their cell, where they are
broken up by cell enzymes. This is called phagocytosis.
lymph system
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The lymph system returns intercellular fluid to the blood system, filters cell debris and produces
white blood cells responsible for the immune response.
cell death to seal off pathogen
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For some pathogens, macrophages and lymphocytes completely surround a pathogen so that it is
enclosed in a cyst. The white cells involved die, so that the pathogen is isolated from its food supply
and also dies.
Identify antigens as molecules that trigger the immune response.
Background: If the previous two systems fail to destroy a pathogen then the immune system comes into
operation. It depends on distinguishing between parts of the body and particles from outside. It is
important that phagocytes are able to make this distinction, otherwise they would destroy body cells.
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Any molecule that the body recognises as being foreign is called an antigen. Antigens activate the
immune response.
Explain why organ transplants should trigger an immune response.
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Organs from another organism are recognised as foreign by the human immune system. The
surfaces of the new organ contain antigens. These trigger an immune response and body attacks
the new organ as if it were a pathogen.
5. The immune response
5. MacFarlane Burnet's work in the middle of the twentieth century contributed to a better
understanding of the immune response and the effectiveness of immunisation programs
Background: Sir Frank Macfarlane Burnet was an Australian scientist who won the Nobel Prize for his
research into physiology. He studied immunology and worked on the development of the influenza
vaccine.
Identify components of the immune response
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antibodies
T cells
B cells
Name
What it is
What it does
antibodies
proteins that the body produces when it
detects antigens. Each different antigen
stimulates the production of its own particular
antibody.
join with antigens so that they are clumped
together and can be more easily recognised and
destroyed by macrophages
B cell
a special kind of lymphocyte produced in the
bone marrow (thus B cell)
When a B cell recognises an antigen, it divides
repeatedly to produce a mass of identical cells
(clones) that work as antibody producers
(plasma cells).
T cell
another kind of lymphocyte, that is passed
through the thymus gland (thus T cell)
Some produce toxic substances that destroy
cells that have been invaded by a virus. Others
help the B cells to divide rapidly.
Describe and explain the immune response in the human body in terms of:
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o
o
interaction between B and T lymphocytes
the mechanisms that allow interaction between B and T lymphocytes
the range of T lymphocytes types and the difference in their roles
Interaction between B and T lymphocytes
B and T lymphocytes interact as they are both attacking the same antigen. Helper T cells (see below)
stimulate B cells and T cells to clone.
The mechanisms that allow interaction between B and T lymphocytes
The T lymphocytes that help B lymphocytes are called helper T cells (Th cells). If a B cell has an antigen on its
surface, there is a risk that a T cell will recognise the antigen and attack it together with the B cell. This
does not happen because T cells are able to recognise “self” molecules that are on the surface of B cells.
Every person has their own particular "self" molecules, so there are millions of different B cells. They are
like personal identity used to identify cells to T lymphocytes. This means that, in the case of organ
transplants, T cells can recognise cells that have come from a different body and so help B cells to destroy
them. Only identical twins have the same “self” molecules on their B cells.
The range of T lymphocytes types and the difference in their roles
Type of T cell
Roles
killer T cells (Tc cells)
attack and destroy macrophages that have engulfed an antigen. They produce
cytotoxins.
helper T cells (Th cells)
secrete chemicals that stimulate cloning in B and T cells
memory T cells
remain in the body and reactivate quickly with subsequent infections by the same
antigen
suppressor T cells
stop the reaction when the antigen is destroyed
Outline the reasons for the suppression of the immune response in organ transplant patients
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When an organ is transplanted it is recognised by the immune system in the body as non-self. The
body attacks the new organ as if it is an invading pathogen. To overcome this problem, transplant
patients are given powerful drugs to suppress their natural defences. This can lead to complications,
as the patient has reduced defences against any pathogen that they may encounter.
Process, analyse and present information from secondary sources to evaluate the effectiveness of
vaccination programs in preventing the spread and occurrence of once common diseases, including small
pox, diphtheria and polio
Background: Vaccination gives artificially acquired immunity from a disease. Once common diseases, such
as small pox, diphtheria and polio, are now uncommon because of successful vaccination programs.
Smallpox was the first disease for which a vaccine was developed. Edward Jenner did this in 1796. The
vaccination program that was started in the 1960s was so successful that the World Health Organisation
(WHO) has declared it eradicated. Diphtheria vaccine is given as part of a triple antigen injection that
protects against diphtheria, tetanus and whooping cough. In 1990, WHO stated that 80% of children had
been vaccinated against this disease. There continues to be outbreaks of this disease and continued
vaccination is recommended. It is no longer thought of as a major child killer. Polio caused thousands of
children to become paralysed every year. A vaccine was introduced in 1955. It became available as an oral
vaccine in the 1960s. Worldwide, the number of cases is down by 80%.
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Use the Internet, biology text books and encyclopedias to gather information on the use of vaccines
over the last 200 years and on the use of vaccines in controlling common diseases. Make sure you
gather information on small pox, diphtheria and polio. Numerical data or graphs are particularly
useful for the evaluation purposes.
Assess the reliability of secondary information and data by considering information from various
sources. This is an ideal opportunity to process claims about the effectiveness of vaccination made
in the mass media.
Analyse information by identifying trends or contradictions.
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Present your findings as an evaluation report. Consider such aspects as how vaccination programs
are implemented in Australia and different parts of the world. Discuss the problems associated with
producing and using vaccines, especially in less developed countries. Comment on the effectiveness
of vaccination. Consider using graphs to demonstrate the points you make.
Outline the way in which vaccinations prevent infection
Background: When a person has had an infection, some of the B cells produced in response to the
pathogen are stored in the lymphatic tissue. They are called memory B cells. They are ready to provide a
very rapid response if the same pathogen later attacks the body.
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Vaccination is a way of giving a person the “experience” of having had an infection without actually
having it, so that the body responds to the “experience” by producing the appropriate memory B
cells.
The way in which the “experience” is given depends on the pathogen. In the case of small pox a
very similar, but very much less harmful pathogen (cow pox), was used. In other cases, the virus is
made weaker, and therefore harmless (attenuated), before being used in a vaccine. Examples of
this type of vaccine are those for poliomyelitis, measles and whooping cough.
Many pathogenic bacteria are harmful to the body because of the toxins they produce. For
diphtheria these toxins are modified to produce the vaccine.
Whatever the source of the vaccine, the effect is the same. It introduces antigens into the body so
that B cells are activated to produce large amounts of antibody and B cells that are stored in the
lymph system are ready for a future attack by the particular pathogen.
6. Epidemiological Studies
6. Epidemiological studies involve the collection and careful statistical analysis of large quantities of
data. Such studies assist the causal identification of non-infectious diseases
Background: An epidemic is an outbreak of a disease that affects a large number of people in a particular
place at the same time. Epidemiology is the study of epidemics, especially by looking for common factors in
populations affected by the disease. It is based on careful collection and analysis of statistical information.
Gather, process and analyse information to identify the cause and effect relationship of smoking and
lung cancer
Background: Cause and effect is difficult to establish. For example, it is one thing to say that everyone with
a certain disease also watches television, but to make the next step, and say that television caused the
disease, is not possible. There could be any number of other possible causes for the disease. This difficulty
arises with epidemiological studies. Smoking and lung cancer have been linked by research time after time
but it is difficult to get the manufacturers of tobacco products to accept that it is a direct cause and effect
relationship, that is, smoking causes lung cancer.
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Use the Internet to gather information on lung cancer. Make sure the information provides
examples of or discusses the results of epidemiological studies.
Process the information to identify statistics that can be used to demonstrate a possible link
between cause and effect for the disease chosen.
Analyse the information to decide how the cause and effect relationships demonstrated in
epidemiological studies can be used to identify the cause of the disease.
Identify and describe the main features of epidemiology using lung cancer as an example

Epidemiological studies need to investigate cause and effects of a disease. To be valid they must:
o focus on large groups of people rather than individuals and relate to a target population that
can be identified. This allows statistics to be used to identify trends and possible causative
factors.
o use populations where there is occurrence of the disease and where there are unequal
exposures to the suspected or possible causes. No conclusions about the effect of smoking
could be drawn from a group of people who each smoke 20 cigarettes a day
o allow for analysis of factors that might contribute to the occurrence of the disease among
those afflicted, such as age, sex, ethnic group, and occupation.
Identify causes of non-infectious disease using an example from each of the following categories:
o
o
o
inherited diseases
nutritional deficiencies
environmental diseases
Inherited diseases

Inherited diseases result from mutations that lead to the production of different or faulty enzymes,
resulting in impaired body function.
Examples
Examples of inherited diseases are Down syndrome, colour blindness, haemophilia, phenylketonuria,
thalassaemia and sickle cell anaemia.
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Down syndrome is an inherited disease that is caused by the non-disjunction of chromosome 21.
This results in three chromosomes and not the usual two (trisomy 21). People with Down syndrome
have a characteristic appearance and may have a shortened life span. Mothers who have children
later in life are more prone to produce Down syndrome children.
Nutritional deficiencies

The effect of nutritional deficiencies depends on the kind of deficiency. In some parts of the world
diets may be deficient in certain elements, such as iodine, copper, iron or zinc.
Examples
Examples of nutritional diseases are scurvy, rickets, goitre, kwashiorkor and beri beri.
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Scurvy is caused by a deficiency in vitamin C. Symptoms include bleeding gums and tooth loss. It is
treated by increasing the intake of food and drinks containing vitamin C, such as citrus fruit.
Rickets is a metabolic bone disease resulting from a deficiency of Vitamin D. This can be due to a
lack of sufficient vitamin D in the diet or due to insufficient exposure to sunlight. The disease is
called osteomalacia when it occurs in adults.
Environmental diseases

Environmentally caused diseases include those due to lifestyle, such as smoking-related diseases, as
well as those caused by something in the environment, such as lead or substances that cause
allergies.
Examples
Examples of environmental diseases include smoking-related diseases, Minamata disease, lead or
asbestos related diseases and melanoma.
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Mesothelioma is caused by exposure to asbestos and patients don't get any symptoms until 20 to
30 years after exposure. There is no cure and treatment can only slow down the progression of the
disease.
Identify data sources, plan and perform a first hand investigation or gather information from secondary
sources to analyse and present information about the occurrence, symptoms, cause,
treatment/management of a named non-infectious disease
If you know someone with a non-infectious diseases, you could ask their permission to interview them and
then carry out a first-hand investigation of the disease.
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If this is the case, begin by determining the type of data that needs to be collected through
interview and what information you may need to collect from secondary sources. Consider how you
might analyse the information to make it useful in generalising about the occurrence, symptoms,
cause and treatment or management of the disease.
Plan your investigation so that valid and reliable information is collected. You may need to research
some issues from secondary sources, particularly if your subject is uncertain about particular
aspects required.
Perform your investigation by conducting the interviews and compiling a report. You could
summarise your findings in a table format, like the one below.
If you complete this syllabus point using secondary sources, you could:
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choose a non-infectious disease from one of the categories listed in the previous section.
gather information from a range of resources, including popular scientific journals, digital
technologies like CD-ROMs and the Internet.
analyse the information to make a generalisation for each of the factors being examined.
present a summary using a table like the one below.
Name of disease
Occurrence
Symptoms
Cause
Treatment or
management
7. Modern strategies
7. Increased understanding has led to the development of a wide range of strategies to prevent and
control disease
Background: Modern knowledge of disease has led to the development of a wide range of strategies to
prevent and control disease.
Discuss the role of quarantine in preventing the spread of disease and plants and animals into Australia
and across regions of Australia.
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Australia has generally been fortunate in preventing the spread of plant and animal disease from
other parts of the world because of its geographical isolation. Quarantine seeks to prevent the
entry of harmful diseases into Australia and to stop the spread of diseases within Australia.
These diseases cause huge financial losses to farmers in other countries. Australia is able to sell its
products to overseas markets because of the absence of diseases, like mad cow disease and footand-mouth.
Australia also has declared fruit-fly free areas where the produce is sold with a guarantee of no fruit
fly. This can be done by having inspections and bins to put fruit in when entering particular fruit
growing areas.
Perform an investigation to examine plant shoots and leaves and gathering first hand information of
evidence of pathogens and insect pests
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To perform this investigation, you may need some background information to aid identification of
the pathogens. Use gardening books or the Internet to gather pictures of plant diseases.
When you know what several plant diseases look like, go to an area of vegetation (such as a garden,
park or area of bush) and examine plant shoots and leaves to gather evidence of plant diseases
caused by pathogens or insect pest attack. You should aim to identify at least two examples of
pathogens and insect pests if possible. Look for black patches on the leaves, white powdery residue
or other spots that indicate a pathogen such as a fungus, or holes in the leaves caused by insect
pests such as caterpillars. Use a hand lens to observe the symptoms.
For each example, record observations systematically and use the evidence to suggest what kind of
organism has caused the disease.
Explain how one of the following strategies has controlled and/or prevented disease:
o
o
o
public health programs
pesticides
genetic engineering to produce disease resistant plants and animals
Public health programs

These provide quarantine, sanitation, safe drinking water and immunisation. They are also
responsible for advertising campaigns that target cancer and AIDS. Examples of successful health
campaigns are the Slip! Slop! Slap! skin cancer advertisements, the advertisements that show
various diseases that can be caused by smoking and the Grim Reaper series for education about
AIDS.
Pesticides
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Pesticides, such as DDT, have been used to destroy mosquitoes, which are the vectors of some
diseases, such as malaria and dengue fever.
A good example of a strategy to control or prevent disease is the pesticide control of the disease
malaria. Adult mosquitoes can be destroyed by chemicals such as DDT, dieldrin, or by safer
chemicals, such as pyrethrums. In 1956, the World Health Organisation was responsible for a major
campaign using a residual form of DDT. DDT has been banned in many countries of the world
because of its harmful ecological effects, but it is still used for mosquito eradication in malarial
areas. This has rid many areas of the world from malaria but has unfortunately not reduced it
globally and malaria is still a major killer of children today. Many areas have DDT-resistant
mosquitos. Other pesticides, such as organophosphates and pyrethrums, have become popular. In
some areas, bed nets have been sprayed with pyrethrums and have been found to be effective in
controlling mosquitoes.
Genetic engineering to produce disease resistant plants and animals

Genetically engineered plants can now kill their own pests because of the insertion of a gene from a
soil bacterium, Bacillus thuringiensis (Bt). Bt cotton was the first genetically engineered crop grown
in Australia. The bacteria contain a gene that produces chemicals that kill certain insects. By taking
that gene from the bacteria and inserting into the genome of plants, the plants now produce the
chemical that will kill insect pests.
Gather, process information and use available evidence, to discuss the changing methods of dealing with
plant and animal diseases, including the shift in emphasis from treatment and control to management or
prevention of disease
Background: There has been a shift from waiting for a disease to occur, to preventing the occurrence of the
disease. This can be seen in agriculture where genetically resistant crops are grown so that the plants do
not have to be sprayed for diseases later in life. Animal and plant diseases have been managed by
quarantine restrictions in Australia. Diseases, such as foot and mouth, rabies and plum pox, are managed
by not allowing infected organisms to enter the country. World-wide immunisation has caused diseases
such as small pox to be eradicated.
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Consider all the aspects of the disease you have studied. Make notes on those aspects that relate to
the above syllabus statement.
Using these notes, plan a discussion of the changing methods of dealing with plant and animal
diseases.
Decide whether you need further information, and if so, gather it from textbooks or the Internet.
Write a short concise response from the available evidence to show what you deduce about the
shift in emphasis from treatment and control to management or prevention of disease. Make sure
the response has:
o an introductory paragraph, written in general terms
o a series of paragraphs that focus on specific issues. Each paragraph could discuss any
debatable issues, e.g. advantages and disadvantages of a particular approach
o a concluding statement, providing your position or recommendations based on your
evaluation.
Process and analyse information from secondary sources to evaluate the effectiveness of quarantine in
preventing the spread of plant and animal disease into Australia or across regions of Australia
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Use the Internet to obtain and process information from a range of sources, including the
Australian Quarantine and Inspection Service (AQIS) about the control of the movement of plants
and animals and their products into Australia and within Australia. Quarantine prevents entry of
goods that may carry diseases or pests at airports and seaports. Affected goods are destroyed.
Fumigation is also part of the quarantine program.
Analyse this information to evaluate the effectiveness of quarantine regulations in Australia, being
sure to identify relationships as well as contradictions in the information.