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A-level biology > Module 4 - Disease and the Immune System > Flashcards

Module 4 - Disease and the Immune System Flashcards

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1
Q

What is a disease?

A

A condition that impairs the normal functioning of an organism

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2
Q

What is a pathogen?

A

an organism that causes disease

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3
Q

Give four different types of pathogen

A

Bacteria, viruses, fungi, protoctista

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4
Q

What is a communicable disease?

A

A disease that can spread between organisms

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5
Q

What diseases are caused by bacterium?

A

Tuberculosis
Bacterial meningitis
Ring rot

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6
Q

What diseases are caused by a virus?

A

HIV/AIDS
Influenza
Tobacco mosaic virus

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7
Q

What diseases are caused by fungus?

A

Black sigatoka
Ringworm
Athlete’s foot

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8
Q

What diseases are caused by protoctists?

A

Potato/tomato late blight

Malaria

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9
Q

How can direct transmission occur?

A

Droplet infection
Sexual intercourse
Touching an infected organism

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10
Q

How are diseases passed through indirect transmission?

A

Via an intermediate such as:

Air, water, food or another organism (known as a vector)

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11
Q

What three things can affect the transmission of communicable diseases?

A

Overcrowding
Climate
Human social factors

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12
Q

How does overcrowding affect the transmission of communicable diseases?

A

E.g. TB is spread through droplet infection
Also spread indirectly as the bacteria can remain in the air for long periods of time and infect new people
Risk of infection is increased when lots of people live crowded together in a small space

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13
Q

How does climate affect the transmission of communicable diseases?

A

E.g. Potato/tomato late blight is especially common during wet summers because the spores need water to spread
E.g. Malaria is most common in tropical countries, which are humid and hot
This is because these are the ideal conditions for mosquitoes to breed

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14
Q

How do social factors affect the transmission of communicable diseases?

A

The risk of HIV infection is high in places where there’s limited access to:
Good healthcare - people are less likely to be diagnosed and treated for HIV and the most effective anti-HIV drugs are less likely to be available to the virus is more likely to be passed on to others
Good health education - to inform people about how HIV is transmitted and how it can be avoided e.g. through safe sex practices

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15
Q

Give 6 barriers animals have to prevent against infection

A 
Skin
Mucous membranes 
Blood clotting
Inflammation 
Wound repair 
Expulsive reflexes
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16
Q

How does the skin act as a primary, non-specific defence?

A

It acts as a physical barrier, blocking pathogens from entering the body
Also acts as a chemical barrier by producing chemicals that are antimicrobial and can lower pH, inhibiting the growth of pathogens

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17
Q

How do mucous membranes act as a primary, non-specific defence?

A

Protect body openings that are exposed to the environment

some secrete mucus - a sticky substance that traps pathogens and contains antimicrobial enzymes

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18
Q

How does blood clotting act as a primary, non-specific defence?

A

A mesh of protein fibres, plug wounds to prevent pathogen entry and blood loss

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19
Q

How are blood clots formed?

A

in a series of chemical reactions when platelets are exposed to damaged blood vessels

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20
Q

How does inflammation act as a primary, non-specific defence?

A

Triggered by tissue damage - the damaged tissue releases molecules, which increase the permeability of the blood vessels
They start to leak fluid into the surrounding area
Causes swelling and helps isolate any pathogens that may have entered the damaged tissue #
Molecules cause vasodilation, increases blood flow, makes area hot and brings white blood cells to the area to fight off any pathogens that may be present

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21
Q

How does wound repair act as a primary, non-specific defence?

A

The skin is able to repair itself in the event of injury and re-form a barrier against pathogen entry
Surface repaired by the outer layer of skin cells dividing and migrating to the edges
Tissue below wound contracts to bring edges of wound closer together
Repaired using collagen fibres
Too many collagen fibres and you end up with a scar

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22
Q

How do expulsive reflexes act is primary, non-specific defences?

A

E.g. Coughing, sneezing
Sneeze happens when mucous membranes in the nostrils are irritated
Cough stems from irritation in the respiratory tract
Both are an attempt to expel foreign objects, including pathogens, from the body
They happen automatically

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23
Q

Give three defences plants have against disease

A

Waxy cuticle
Cells themselves surrounded by cell walls
Produce polysaccharide called callose

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24
Q

How does the waxy cuticle of plants protect them against disease?

A

Provides a physical barrier against pathogen entry
Stops water collecting on the leaf, which could reduce the risk of infection by pathogens that are transferred between plants in water

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25
Q

How does the cell wall help to protect plants against disease?

A

Form a physical barrier against pathogens that make it past the waxy cuticle

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26
Q

How does the polysaccharide callose help protect a plant against disease?

A

Callose deposited between plant cell walls and plasma membranes during times of stress e.g. Pathogen invasion
Callose deposition makes it harder for pathogens to enter cells
Callose deposition at the plasmodesmata may limit the spread of viruses between cells

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27
Q

What chemical defended do plants have against disease?

A

Produce antimicrobial chemicals which kill pathogens or inhibit their growth
Secrete chemicals that are toxic to insects - reduces amount of insect-feeding on plants therefore reduces the risk of infection by plant viruses carried by insect vectors

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28
Q

What are antigens?

A

Molecules (usually proteins or polysaccharides) found on the surface of cells

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29
Q

How do antigens react to foreign pathogens?

A

Pathogen invades body, antigens on its cell surface are identified as foreign which activates cells in the immune system

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30
Q

What are the 4 main stages in the Immune Response?

A

1) phagocytes engulf pathogens
2) phagocytes activate T lymphocytes
3) T lymphocytes activate B lymphocytes which divide into plasma cells
4) plasma cells make more antibodies to a specific antigen

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31
Q

How does a phagocyte engulf a pathogen?

A

Phagocyte recognises the antigens on the pathogen
Cytoplasm of phagocyte moves round the pathogen, engulfing it
Made easier by the presence of opsonins
Pathogen now contained in a phagosome
A lysosomes fuses with the phagosome, the enzymes break down the pathogen
Phagocyte presents the pathogen’s antigens
Sticks the antigens on its surface to activate other immune system cells
Called an antigen presenting cell

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32
Q

What are opsonins and how do they work?

A

Molecules in the blood that attach to foreign antigens to aid phagocytosis
They work in different ways:
Some hide the negative charges on the membrane of the pathogen, making it easier for the negatively-charged phagocyte to get closer to the pathogen

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33
Q

What are neutrophils?

A

A type of phagocyte
They are the first white blood cells to respond to a pathogen inside the body
Move towards a wound in response to signals from cytokines
Cytokines are released by cells at the site of the wound

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34
Q

How do phagocytes activate T lymphocytes?

A

T lymphocyte (another type of white blood cell), surface covered with receptors
Receptors bind to antigens presented by APC’s
Each T lymphocyte has a different receptor on its surface
Receptor on the surface of a T lymphocyte meets a complimentary antigen, it binds to it - so each T lymphocyte will bind to a different antigen
Activates T lymphcyte - process called clonal selection
T lymphocyte undergoes clonal expansion - divides to produce clones of itself
Diff types of T lymphocytes carry out different functions

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35
Q

What are the three different types of T lymphocytes?

A

T helper cells
T killer cells
T regulatory cells

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36
Q

What do T helper cells do?

A

Release substances to activate B lymphocytes and T killer cells

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37
Q

What do T killer cells do?

A

Attach to and kill cells that are infected with a virus

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38
Q

What do T regulatory cells do?

A

Suppress the immune response from other white blood cells

Helps to stop immune system cells from mistakenly attacking the host’s body cells

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39
Q

What do some activated T lymphocytes become?

A

Memory cells

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40
Q

How do T lymphocytes activate B lymphocytes, which divide into plasma cells

A

B lymphocytes are another type of white blood cell
Covered with proteins called antibodies
Antibodies bond to antigens to form an antigen-antibody complex
Each B lymphocyte had a different shaped antibody on its surface
When antibody on surface of a B lymphocyte meets a complimentary shaped antigen, it binds to it - so each B lymphocyte will bind to a different antigen
Together with substances released from T helper cells activates the B lymphocyte
Process is another example of clonal selection
Activated B lymphocyte divides by mitosis into plasma cells and memory cells
Another example of clonal expansion

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41
Q

How does cell signalling work?

A

How cells communicate
Cell may release a substance that binds to the receptors on another cell - causes a response of some kind in the other cell
Important to the immune response because it helps to activate all different types of white blood cells that are needed
T helper cells release interleukins that bind to receptors on B lymphocytes
This activates the B lymphocytes - T helper cells are signalling to the B lymphocytes that there’s a pathogen in the body

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42
Q

How do plasma cells make more antibodies to a specific antigen?

A

Plasma cells are clones of the B lymphocyte
They secrete loads of the antibody, specific to the antigen, into the blood
Antibodies will bind to the antigens on the surface of the pathogen to form lots of antigen-antibody complexes

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43
Q

Describe the structure of the antigen-antibody complex

A

Variable regions of the antibody form the antigen binding sites
The shape of the variable region is complimentary to a particular antigen
Variable region allows flexibility when the antibody binds to the antigen
Constant regions allow binding to receptors on immune system cells
Constant region is the same in all antibodies
Disulphide bridges hold the polypeptide chains of the protein together

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44
Q

How do antibodies help to clear an infection?

A

Agglutination pathogens
Neutralising toxins
Preventing the pathogen binding to human cells

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45
Q

How do agglutinating pathogens help to clear infection?

A

Each antibody has two binding sides
Antibody can bind to two pathogens at the same time
Pathogens become clumped together
Phagocytes then bind to the antibodies and phagocytose a lot of pathogens all at once
Antibodies that behave in this way are known as agglutinins

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46
Q

How do neutralising toxins help to clear an infection?

A

Like antigens, toxins have different shapes
Antibodies called anti-toxins can bind to the toxins produced by pathogens
Prevents the toxins from affecting human cells, so the toxins are neutralised (inactivated)
Toxin-antibody complexes are also phagocytoses

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47
Q

What happens during the primary response?

A

Pathogen enters body for first time
Antigens on its surface activate immune response
Slow because there aren’t many B lymphocytes
Eventually body produces enough of right antibody to overcome infection
Meanwhile person will show signs on infection
T and B lymphocytes produce memory cells
Memory cells remain in the body for a long time
The person is now immune

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48
Q

How do memory T lymphocytes work in the primary response?

A

The remember the specific antigen and will recognise it a second time round

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49
Q

How do memory B cells work in the primary response?

A

Record the specific antibodies needed to bind to the antigen

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50
Q

How does the secondary response occur??

A

The same pathogen enters the body again
Immune system will produce a quicker strong immune response - the secondary response
Clonal selection happens faster
Memory B lymphocytes activated and divide into plasma cells - produce the right antibody to the antigen
Memory T lymphocytes - activated and divide into the correct type of T lymphocytes to kill the cell carrying the antigen
Secondary response often gets rid of the pathogen before you begin to show any symptoms

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51
Q

Why is genetic diversity important?

A

If a population had a low genetic diversity, they might not be able to adapt to a change in the environment and the whole population could be wiped away out by a single event

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52
Q

Why populations may have a low genetic diversity?

A

Isolated populations such as those bred in captivity

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53
Q

What is a locus?

A

A point on a chromosome, often compared to the same point on another chromosome

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54
Q

What is polymorphism?

A

Describes a locus that has two or more alleles

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55
Q

How do you calculate the proportion of polymorphic gene loci?

A

Number of polymorphic gene loci / total number of loci

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56
Q

Why factor affect global biodiversity?

A

Human population growth
Increased use of monoculture in agriculture
Climate change

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57
Q

How does human population growth affect global biodiversity?

A

Habitat loss
Over-exploitation
Urbanisation
Pollution

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58
Q

How does increased use of monoculture in agriculture affect global biodiversity?

A

Habitats are lost as land is cleared to make way for large fields
Local and naturally occurring plants and animals are seen as weeds and pests and are destroyed
Traditional varieties of crop are lost because they don’t make enough money

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59
Q

How does climate change affect global biodiversity?

A

Species need a particular climate to survive
Previously inhabitable area becomes uninhabitable
Species forced to migrate to a more suitable area, causing change in species distribution
If species can’t migrate they could become extinct

60
Q

What two ecological reasons are there for maintaining biodiversity?

A

To protect species, including keystone species

To maintain genetic resources

61
Q

What would happen if one species was lost in an ecosystem?

A

Disruption of food chains

Disruption of nutrient cycles

62
Q

What is a keystone species?

A

A species an ecosystem depends on and without which the ecosystem would change dramatically

63
Q

What everyday products to genetic resources provide us with?

A 
Food and drink 
Clothing
Drugs
Fuels
Other industrial materials
64
Q

What economic reason is there for maintaining biodiversity?

A

To reduce soil depletion

65
Q

How do you prepare a blood sample for examining?

A

Blood smeared on microscope slide
Stains added to make different cells easier to see
Likely to see red blood cells, white blood cells and platelets
Some types of white blood cells have granules in their cytoplasm and other types don’t

66
Q

What is active immunity?

A

Where your immune system makes its own antibodies after being stimulated by an antigen

67
Q

What are the two different types of immunity?

A

Active (natural and artificial)

Passive (natural and artificial)

68
Q

What is natural active immunity?

A

This is when you become immune after catching a disease

E.g. if you have measles as a child, you shouldn’t be able to catch it again in life later

69
Q

What is artificial active immunity?

A

This is when you become immune after you’ve been given a vaccination containing a harmless dose of antigen

70
Q

What is passive immunity?

A

Type of immunity you get from being given antibodies made by a different organism - your immune system doesn’t produce any antibodies of its own

71
Q

What is natural passive immunity?

A

When a baby becomes immune due to the antibodies it receives from its mother, through the placenta and in breast milk

72
Q

What is artificial passive immunity?

A

This is when you become immune after being injected with antibodies from someone else
e.g. if you contract tetanus you can be injected with antibodies against the tetanus toxin, collected from blood donations

73
Q

Briefly summarise active immunity

A

Requires exposure to antigen
It takes a while for protection to develop
Protection is long-term
Memory cells are produced

74
Q

Briefly summarise passive immunity

A

No exposure to antigen
Protection is immediate
Protection is short-term
Memory cells aren’t produced

75
Q

What is an autoimmune disease?

A

A disease where the body misreads its own antigen presenting cells as foreign and attacks them

76
Q

Give an example of two autoimmune diseases

A

Lupus

Rheumatoid arthritis

77
Q

What is lupus?

A

It is caused by the immune system attacking cells in the connective tissues
Damages tissues and causes painful inflammation
Can affect the skin and joints, as well as organs such as the heart and lungs

78
Q

What is rheumatoid arthritis?

A

Caused by the immune system attacking cells in the joints

Again causes pain and inflammation

79
Q

How do vaccines help to protect against disease?

A

Contain antigens that cause your body to produce memory cells against a particular pathogen, without the pathogen causing disease
Means you become immune without getting any symptoms

80
Q

How does vaccination protect against epidemics?

A

If most people in a community are vaccinated the disease becomes rare
This means even the people who haven’t been vaccinated are unlikely to get the disease because there’s no one to catch it from
This is called herd immunity
Helps prevent epidemics - mass outbreaks or disease

81
Q

How are the antigens in a vaccine?

A

Free or attached to a dead or weakened pathogen

82
Q

What is the difference between vaccination or immunisation?

A

Vaccination is the administration of antigens into the body
Immunisation is the process by which you develop immunity
Vaccination causes immunity

83
Q

Give an example of two routine vaccines

A

MMR - protects against measles, mumps and rubella

Meningitis C vaccine - protects against bacteria that cause meningitis C

84
Q

What are antibiotics?

A

Chemicals that kill or inhibit to growth of bacteria

85
Q

Why are antibiotics used?

A

Used by humans as drugs to treat bacterial infections. Useful because they usually target bacterial cells without damaging human body cells

86
Q

What was the first antibiotic to be isolated?

A

Penicillin

87
Q

What are the risks of antibiotics?

A

Can cause side effects, even severe reactions

Big risk is antibiotic resistance

88
Q

Give examples of two antibiotic-resistant bacteria

A

MRSA - causes serious wound infections, resistant to several antibiotics, including meticillin
Clostridium difficile - infects the digestive system usually causing problems with people who have already been treated with antibiotics

89
Q

Why do plants need to be protected for medicinal purposes?

A

Only a small amount of organisms have been investigated so far, biodiversity needs to be protected to allow there to be enough plants to test.

90
Q

What are personalised medicines and how are they used?

A

Genes determine how your body responds to certain drugs
Tailored to your DNA, theory is that if doctors have your genetic information they can use it to predict how you will respond to different drugs
This is because certain drugs are more effective for some people than others

91
Q

What is synthetic biology?

A

Involves using technology to design and make things like artificial proteins, cells and even microorganisms
Allows scientists to look for bacterial which kill cancer cells without damaging human body cells

92
Q

What is biodiversity?

A

The variety of living organisms in an area

93
Q

What is a species?

A

A group or similar organisms able to reproduce to give fertile offspring

94
Q

What is a habitat?

A

The area inhabited by a species
Includes physical factors, like the soil and temperature range, and the living factors like availability of food and presence of predators

95
Q

What is habitat diversity?

A

The number of different habitats in an area

96
Q

What is species diversity?

A

The number of different species (species richness) and the abundance of each species (species evenness) in an area

97
Q

What is genetic diversity?

A

Variation of alleles within a species

98
Q

How do you measure biodiversity?

A

By sampling:
choose area to sample
count no. of individuals of each species
Repeat the process taking as many samples as possible
Use results to estimate the total number of individuals or the total number of different species in the habitat being studied

99
Q

What are the three types of non-random sample?

A

Systematic
Opportunistic
Stratified

100
Q

What is a systematic sample?

A

When samples are taken at fixed intervals, often along a line
e.g. quadrats could be placed along a line (called a transect) from an area of shade in the corner to the middle of the field

101
Q

What is an opportunistic sample?

A

When samples are chosen by the investigator

Used because it is easy to carry out but the data will be biased

102
Q

What is a stratified sample?

A

When different areas in a habitat are identified and samples separately in proportion to their part of the habitat as a whole

103
Q

What is species richness?

A

The number of different species in an area

The higher the number of species, the greater the species richness

104
Q

How is species richness measured?

A

By taking random samples of a habitat and counting the number of different species

105
Q

What is species evenness?

A

A measure of the relative abundance of each species in an area
The more similar the population size of each species, the greater the species evenness

106
Q

How is species evenness measured?

A

Taking random samples of a habitat, counting the number of individuals of each different species

107
Q

How is diversity measures specifically?

A

Using Simpson’s Index of Diversity

108
Q

How can you tell the measure of diversity using Simpson’s index?

A

The number is always between 1 and 0
Closer to 1, the more diverse the habitat
The greater the species richness and evenness, the higher the number

109
Q

Why do we need to maintain biodiversity for aesthetic reasons?

A

Areas rich in biodiversity provide pleasant, attractive landscapes that people can enjoy, by maintaining biodiversity we protect the landscape
also a pretty landscape means more visitors an area is likely to attract

110
Q

Give some methods of in-situ conservation

A

Establishing protected areas such as national parks
Controlling or preventing the introduction of species that threaten biodiversity
Protecting habitats
Promoting particular species
Giving legal protection to endangered species

111
Q

Give an advantage of in-situ conservation

A

Often that both species and their habitat are conserved
Larger populations can be protected
Less disruptive than removing organisms from their habitats

112
Q

Give a disadvantage of in-situ conservation

A

Difficult to control some factors that are threatening a species e.g. poaching, predators, disease or climate change

113
Q

Give some examples of ex-situ conservation

A

Relocating to safer area
Breeding in captivity and reintroducing
Botanic gardens are great for a variety of rare plants
Seed banks

114
Q

Give an advantage of ex situ conservation

A

Protect individual animals in a controlled environment
predation can be managed for easily
Used to reintroduce a species which has left an area

115
Q

Give a disadvantage of ex-situ conservation

A

Only a small number of individuals can be cared for
Difficult and expensive to create and sustain the right environment
Less successful than in-situ methods

116
Q

What are the eight taxonomic groups?

A 
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
117
Q

What are the five kingdoms?

A 
Prokaryote
Protoctist 
Fungi
Plants
Animals
118
Q

What is the binomial naming system and how is it written?

A

The genus and species of the Latin name is given, the genus name has a capital letter at the beginning

119
Q

What is phylogeny?

A

The study of the evolutionary history of groups of organisms

120
Q

Why are observable features not enough when classifying organisms?

A

Sharks and whales look quite similar and they both live in the sea
But they are not closely related
Whales are mammals, sharks are cartilaginous fish
They are in two completely different classes

121
Q

What are classification systems based on?

A 
Observable features along with:
molecular evidence
embryological evidence 
anatomical evidence 
behavioural evidence
122
Q

What has the five kingdoms been replaced by?

A

The three domains
e.g. Eukarya
Archaea
Bacteria

123
Q

What is intraspecific variation?

A

Variation within a species
e.g. robins :
length, wingspan, colour, beak size

124
Q

What is interspecific variation?

A

Variation between different species
e.g. the lightest species of bird is the bee hummingbird
the heaviest species of bird is the ostrich

125
Q

Give an example of continuous variation in animals

A

Milk yield

mass

126
Q

Give an example of continuous variation in plants

A

Number of leaves

Mass

127
Q

Give an example of continuous variation in microorganisms

A

Width

Length

128
Q

Give an example of discontinuous variation in animals

A

Hair colour, eye colour, blood group

129
Q

Give an example of discontinuous variation in plants

A

Colour

Seed shape

130
Q

Give an example of discontinuous variation in microorganisms

A

Antibiotic resistance

Pigment production

131
Q

How can variation occur?

A

The environment, genetic factors, or both

132
Q

How do genetic factors affect variation?

A

Different species have different genes
Same species have same genes, but different alleles
Different in genotype result

133
Q

How do environmental factors affect variation?

A

Climate
food
lifestyle
e.g. accents, whether people have their ears pierced

134
Q

How do both environmental and genetic factors affect variation?

A

Height - genes determine how tall an organism can grow but diet or nutrient availability can affect how tall an organism actually grows
flagellum - genes determine if a microorganism can grow a flagellum but some will only start to grow in certain environments

135
Q

What can you use to look for variation between samples?

A

The mean of data collected

136
Q

What does standard deviation tell you?

A

How much the values in a single sample vary

It is a measure of spread of values about the mean

137
Q

How do adaptations develop?

A

Because of evolution by natural selection

138
Q

How does being adapted to an environment help an organism?

A

It means the organism has features that increase its chances of survival and reproduction

139
Q

Give an example of a behavioural adaptation

A

Possums ‘play dead’ - threatened by a predator, play dead to escape attack, increases chances of survival
Scorpions dance before mating - makes sure they attract the mate of the same species, increasing likelihood of successful mating

140
Q

Give an example of a physiological adaptation

A

Brown bears hibernate - lower their rate of metabolism over winter, conserves energy, don’t need to look for food in the months when it is scarce

141
Q

Give an example of anatomical adaptations

A

otters have a streamlined shape - makes it easier to glide through water, easier to catch prey and escape predators, increasing chances of survival

142
Q

What are marsupial mammals?

A

Short gestation period
don’t develop full placenta
born early in their development and climb into mother’s pouch
here become attached to mother’s teat to receive milk while they continue to develop

143
Q

What are placental mammals?

A

Longer gestation period
develop placenta during pregnancy, allows exchange o nutrients and waste products between fetus and mother
Are born fully developed

144
Q

Give some adaptations of moles

A

Small or non-existent eyes
no external ears, streamline head for burrowing
scoop-shaped and powerful front paws
claws specialised for digging
tube shaped body and cone shaped head, easier to push through sand or soil

145
Q

What observations did Darwin make when developing his theory of evolution

A

Organisms produce more offspring than survive
Variation in characteristics of members of the same species
Characteristics passed from parent to offspring
Best adapted, most likely to survive

146
Q

What was Darwin’s theory?

A

Individuals within population show variation in their phenotypes
Selection pressures create struggle for survival
Better adapted more likely to survive
Better adapted reproduce together, pass their advantageous characteristics to offspring
Over generations, leads to evolution

A-level biology (18 decks)

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