Move into cells and use the biochemistry to makemanycopies of itself
This leads to the cell bursting and releasing all of the copies into the bloodstream
The damage and destruction of the cells makes the individual feel ill
Bacteria
Small
Produce toxins that can damage cells
Protists
Some are parasitic, meaning they use humans and animals as their hosts (live on and inside, causing damage)
Fungi
Can be single celled or have a body made of hyphae (thread-likestructures)
Can produce spores which can be spread to other organisms
Ways pathogens are spread
Directcontact
By water
By air
Direct contact
Touching contaminated surfaces, kissing,contact with bodily fluids, direct skin to skin,microorganisms from faeces,infected plant material left in field
By water
Drinking or coming into contact with dirty water
By air
Pathogens can be carried in the air and then breathed in (a common example is the droplet infection, which is when sneezing,coughing or talking expels pathogens in droplets which can be breathed in)
Ways to reduce the damage of disease
Improving hygiene
Reducingcontact with infected individuals
Vaccination
Improving hygiene
Hand washing, using disinfectants,isolating raw meat, usingtissues and handkerchiefs when sneezing
Herd immunity
When a largeproportion of the population is vaccinated, the spread of the pathogen is reduced as there are less people to catch the disease from
Measles
Symptoms: Fever and red skinrash, can lead to other problems such as pneumonia (lung infection), encephalitis (brain infection) and blindness
How it is spread: Droplet infection
How it is being prevented: Vaccinations for young children to reduce transmission
HIV
Symptoms: Initially flu-like symptoms, then the virus attacks the immune system and leads to AIDS (a state in which the body is susceptible to many different diseases)
How it is spread: By sexual contact or exchange of bodily fluids such as blood
How it is being prevented: Using condoms, not sharing needles, screening blood when it is used in transfusions, mothers with HIV bottle-feeding their children instead of breastfeeding, use of antiretroviral drugs (stop the virus replicating in the body)
Gonorrhoea
Symptoms: Thick yellow or greendischarge from the vagina or penis, pain when urinating
How it is spread: It is a sexuallytransmitted disease spread throughunprotected sexual contact
How it is being prevented: By usingcontraception such as condoms and antibiotics (used to be treated with penicillin but many resistant strains are developing)
Rose black spot
Symptoms: Purple or black spots on leaves of rose plants, reduces the area of the leaf available for photosynthesis, leaves turn yellow and drop early
How it is spread: The spores of the fungus are spread in water (rain) of by wind
How it is being prevented: By using fungicides or stripping the plant of affected leaves (have to be burnt)
Malaria symptoms: Fevers and shaking - when the protists burst out of blood cells
How it is spread: The vector is the female Anopheles mosquito, in which the protists reproducesexually. When the mosquito punctures the skin to feed on blood, the protists enter the humanbloodstream via their saliva.
How it is being prevented: Using insecticide coated insectnets while sleeping, removing stagnant water to prevent the vectors from breeding, travellers taking antimalarial drugs to kill parasites that enter the blood
The skin
Acts as a physicalbarrier
It produces antimicrobial secretions to kill pathogens
Good microorganisms known as skin flora compete with the bad microorganisms for space and nutrients
The nose
Has hairs and mucus (sticky substance) which prevent particles from entering your lungs
The trachea and bronchi
Secrete mucus in order to trap pathogens
Cilia (hair-like structures on cells) beat to waft mucus upwards so it can be swallowed
The stomach
Produces hydrochloricacid that kills any pathogens in your mucus, or food and drink
Ways the specific immune system protects you
Phagocytosis (engulfing and consuming pathogens)
Producing antibodies
Producing antitoxins
Phagocytosis
This destroys pathogens, meaning they can no longer make you feel ill
Producing antibodies
Each pathogen has an antigen on their surface, which is a structure which a specific complementaryantibody can bind to. Once antibodies begin to bind to the pathogen, the pathogens start to clump together, resulting in it being easier for whitebloodcells to find them.
If you become infected again with the same pathogen, the specific complementary antibodies will be produced at a faster rate. The individual will not feel the symptoms of the illness. They are said to be immune.
Producing antitoxins
They neutralise the toxins released by the pathogen by binding to them
Vaccination
The vaccine contains a dead or inactivated form of the pathogen
This stimulates white blood cells to produce antibodies complementary to the antigens on the pathogen
Painkillers
Only treat the symptoms of the disease, rather than the cause
The great concern is that bacteria are becoming resistant to antibiotics
Antibiotic resistance
Mutations can occur during reproduction resulting in certain bacteria no longer being killed by antibiotics
When these bacteria are exposed to antibiotics, only the non-resistant one die
The resistant bacteria survive and reproduce, meaning the population of resistant bacteria increases
This means that antibiotics that were previously effective nolongerwork
Ways to prevent antibiotic resistance
Stop overusingantibiotics
Finishing courses of antibiotics to kill all of the bacteria
Epidemics (lots of cases in an area) can be prevented through herdimmunity
Badreactions (such as fevers) can occur in response to vaccines (although very rare)
To prevent the development of these resistant strains
Stop overusingantibiotics- this unnecessarily exposes bacteria to the antibiotics
Finishing courses of antibiotics to kill all of the bacteria
Plants can also be affected by viral,bacterial and fungal pathogens
Common signs of plant diseases
Stunted growth: indicating nitrate deficiency
Spots on leaves: indicating black spot fungus on roses
Areas of decay: black spot fungus on roses,blights on potatoes
Abnormal growths: crown galls caused by bacterial infection
Malformed stems or leaves: due to aphid infestation
Discolouration: indicating magnesium deficiency, or tobaccomosaicvirus
Pests on leaves: such as caterpillars
Physical defences of plants
Tough waxy cuticle stops entry into leaves
Cellulose cell walls form a physical barrier into the cells
Plants have layers of dead cells around stems (such as bark) which stop pathogens entering. The dead cells fall off with the pathogens