Module 4

Question 1

What is a communicable disease?

Answer 1

illnesses resulting from the infection, presence and growth of pathogens in an individual host

Question 2

What is a pathogen?

Answer 2

a disease causing organism which takes nutrition, energy and protection from and damages its host. (parasite)

Question 3

What type of cell is bacteria? How are they classified?

Answer 3

prokaryotes classified by shape- rod (bacilli), spherical (cocci), comma shaped (vibrios), spiralled (spirilla) and corkscrew (spirochaetes)

By cell walls- 2 main types have different structures that react differently to gram staining Gram positive- look purple/ blue and Gram negative look red. The cell wall affects how they react to antibiotics

Question 4

What is the chain of infection?

Answer 4

infective agent (pathogen)- bacteria, virus, protoctists, fungi

source of infection- the reservoir is the location of the microorganism which must meet needs of pathogen to grow and survive

mode of transmission- direct (skin to skin, bodily fluids) or indirect (pathogen transferee to intermediate that’s not infected but transfers pathogen to host (airborne droplets, insects)

susceptibility of host- young, elderly and those with underlying health conditions often have weaker immune systems

Question 5

Are viruses living?

What structure do they have?

How do they replicate?

How do they evolve?

What are bacteriophages?

Answer 5

non living and very small

Have DNA/RNA surrounded by a protein

they invade living cells and their genetic material takes over the biochemistry of the host to make more viruses

They evolve my adapting to their host

They can even attack bacteria, using them to replicate and killing them at the same time

Question 6

What type of cell are protocista? How do they infect?

Answer 6

Eukaryote parasitic using people/ animals as host

Question 7

What type of cell are fungi?

what is their cell wall made of?

How do they absorb nutrients?

what type of fungi are pathogenic?

How do they affects plants?

How do they spread?

Answer 7

Eukaryote

cell wall of chitin

Can photosynthesise so digest food extracellularly before absorbing nutrients- saprophytic feeders. parasitic ones are as they live off organic matter

stop them photosynthesising as they affect the leaves

when they reproduce they produce millions of tiny spores

Question 8

Bacterial animal disease

• Name of pathogen
• method of transmission
• symptoms/ method

Answer 8

• Tuberculosis
• mycobacterium tuberculosis
• Direct- droplets through air
• Lung tissue destroyed, immune system suppressed, coughing, fever, fatigue
• Bacterial meningitus
• Neisseria meningitidis, haemophilis influenzae
• direct- droplets though air and exchange of fluids In meninges (tissue surrounding brain to prevent entry of bacteria) of brain but can spread causing blood poisoning and death. Blotchy red rash that doesn’t disappear when a glass is pressed against it shows blood poisoning. Nausea, vomiting, fever, headache, muscle pain

Question 9

Virus animal disease

• Name of pathogen
• method of transmission
• symptoms/ method

Answer 9

HIV/AIDS

• Human immunodeficiency virus (HIV)
• Direct- contact with bodily fluids, mother to child in breast milk
• Targets T cells in immune system and contains enzyme reverse transcriptase which transcribes RNA to a single strand of DNA in the host cell. HIV is a retrovirus as the process is opposite to usual.
• Flue like illness, fatigue, join and muscle pain

Influenza

• Influenza A, B and C
• Direct- droplets in air
• Sudden fever, body ache, fatigue, dry cough, kills cilia allowing airways to be infected

Question 10

Protoctist animal disease

• Name of pathogen
• method of transmission
• symptoms/ method

Answer 10

• Malaria
• Plasmodium falciparum
• indirect- female anopheles mosquito.
• reproduce in mosquito then invade red blood cell then liver
• High temperature, headache, vomit, muscle pain, diarrhea

Question 11

Fungus animal disease

• Name of pathogen
• method of transmission
• symptoms/ method

Answer 11

Cattle ringworm

• Trichophyton verrucosum
• Direct- contact with infected cattle
• grey white areas of skin with ashy circular areas. may be itchy

Athletes foot

• Epidermophyton floccosum, trichopyton rubrum, T. Mentagrophytes
• direct- contact with towels used by infetced people.
• Grows on and digests warm moist skin between toes causing cracking and scaling- itchy and sore

Question 12

Bacterial plant disease

• Name of disease
• host plant
• names of pathogen
• Method of transmission
• Symptoms

Answer 12

• Ring Rot
• Potato, tomato
• clavibacter, michiganensis
• Direct contact with infected tubers, cultivation spreads it as bacteria remain of machinery damages leaves, tubers and fruit. Infects vascular tissue and blocks them so no water can enter leaves. Once a field is infected can’t grow potatoes for 2 years

Question 13

Viral plant disease

• Name of disease
• host plant
• names of pathogen
• Method of transmission
• Symptoms

Answer 13

• mosaic
• Tobacco Tobaco mosaic virus (TMV)
• direct- contact with leaves of infected plants
• indirect- via aphids as vectors
• damages leaves, flowers and fruit, stunting growth. Yellow mosaic pattern on leaves. spreads though plasmodesmata and phloem

Question 14

Fungus plant disease

• Name of disease
• host plant
• names of pathogen
• Method of transmission
• Symptoms

Answer 14

Black sigatoka

• bananas
• mycosphaerella fijiensis
• direct- spores are dispersed through air and spores germinate and grow into leaf through stomata. they are also present in soil
• indirect- fungus on infected plant releases spores and an insect eating the plant picks up the spores and transmits to other plants when it feeds
• yellow spots and black streaks. Hyphae penetrate and digest cells so leaves go black as can’t photosynthesise

Question 15

Protocist plant disease

• Name of disease
• host plant
• names of pathogen
• Method of transmission
• Symptoms

Answer 15

• late blight
• potato, tomatoes
• phytophthora infestans
• direct- swimming zoospores and aerial spores
• hyphae penetrate host cells and destroy leaves, tubers and fruit.
• Blue/ grey spots, shrivel and go brown

Question 16

disease transmission

why is it not always successful?

Answer 16

the transfer of pathogens from an infected host to an uninfected one

large numbers of pathogen produced to reach chances of reaching a host

infective stages are small to avoid wasting energy

Question 17

Direct transmission:

Answer 17

CONTACT: between individuals TMV, RINGROT, RINGWORM kissing or bodily fluid contact HIV, microorganisms from faeces transmitted to hands

SPORES: BLACK SIGATOKA, LATE BLIGHT. Insects carry spores so could be indirect

INGESTION: contaminated food and drink, mouth to hands

ANIMAL BITES/ PUNCTURE WOUNDS (inoculation)

Question 18

Indirect transmission:

Answer 18

VECTORS:

• wind carries spores
• water allow spores to swim in surface film of water on leaves
• animals carry pathogens and spores from one plant to another when they feed
• humans transmit pathogens and spores by hands, clothing, farming, transporting plants around the world

MALARIA, TMV

DROPLETS: of saliva and mucus in the air when you cough, sneeze and talk contain pathogens and can be inhaled by others

TB, MENINGITIS, FLU

FOMITES: inanimate objects transfer pathogens like door handle and towel

ATHLETES FOOT

WATER maybe soil

Question 19

Factors affecting direct transmission animals and plants:

Answer 19

Animals/ human: close proximity like schools, hospitals and cramped housing- poverty

Plant: High density monocultures of crop plants

Question 20

Factors affecting indirect transmission animals and plants:

Answer 20

climate and weather- damp and warm is good for vectors, especially mosquitos. Aphids and mosquitos need 20*c and over. Climate change worsens this as increased rain and wind increases spread, animals vectors are spread to new areas, but drier conditions in some areas could reduce spread there

Question 21

Factors that affect transmission of human diseases

Answer 21

• poor nutrition
• compromised immune system
• poor waste disposal creates breeding sites for vectors
• culture and infrastructure- medical practices socioeconomic- lack of trained HC workers
• warning when outbreak
• poor sanitation and sewage
• housing contaminated water
• travel and migration bring diseases to populations with no natural resistance or immunity behaviour
• sexually transmitted diseases can be lowered depending on number of partners

Question 22

Preventing spread of plant diseases:

Answer 22

leave space between plants

rotate crops (bacteria/spores die if no host)

strict hygiene- wash hands, boots machinery control insect vectors ?????

plant crops less susceptible to disease

plenty of minerals so healthier plants with more tolerance to infection

Question 23

retrovirus

Answer 23

a virus like HIV with single stranded RNA as its genetic material, not DNA. when the retrovirus invades a host cell it uses its enzyme reverse transcriptase to make DNA from RNA template. Other RNA viruses like influenza don’t use their RNA as a template for making DNA

Question 24

what is a vector:

Answer 24

an organism that transfers a pathogen from an infected host to an uninfected host and is not harmed by the pathogen itself

Question 25

protoctist definiton

Answer 25

a eukaryotic unicellular organism

Question 26

epidemic

endemic

pandemic

Answer 26

widespread occurrence of infectious disease in community at a particular time

a disease or condition regularly found in particular people/ place

a disease prevalent over a whole country or world

Question 27

Comparing primary defences in plants and animals:

permanent physical barrier against infection:

prevent entry of pathogens:

Block movement of pathogens:

Use chemicals:

Answer 27

cellulose cell walls, skin

stomata closing, blood clots around open wound in skin

tyloses and calls, musus and cilia to remove

terpenes, HCL and lysosomes to kill pathogens

Question 28

first line of defence

Answer 28

physical and chemical defences that prevent entry of pathogens into the body

Question 29

Non specific defences

Answer 29

work the same way whatever the pathogen and are present from birth

Question 30

How does the skin work as a primary defence?

Answer 30

• Impermeable to most pathogens with a keratinised layer of dead epithelial cells. - Hostile conditions as lactic acid and fatty acids are secreted from sweat and sebaceous glands are acidic. When sweat evaporates it leave salty, dry conditions combined with low pH prevent microorganisms growing and multiplying. - Skin floral healthy microorganisms that outcompete pathogens for space on surface. Also inside body like intestines

Question 31

Primary defences

Answer 31

skin

mucous membranes

expulsive reflexes

other

Question 32

Mucous membranes

Answer 32

Line parts of the body likely to come into contact with pathogens eg. airways, digestive tract, genital tracts mucous is secreted by goblet cells in the epithelium and traps pathogens its sticky because its full of glycoprotein molecules which have long carbohydrate chains and contains antimicrobial enzymes cilia on ciliated epithelium in airways waft mucus up where it is swallowed

Question 33

Expulsive reflexes

Answer 33

coughing and sneezing ejects pathogen-laden mucus from gas exchange system areas prone to infection are sensitive to dust, microorganisms or the toxins they release ? happen automatically to expel foreign bodies

Question 34

Other primary non specific defences:

Answer 34

lysozymes destroy bacterial and fungal cell walls and are found in blood, sweat, tears and phagocytes remove remaining pathogens.

acidic conditions of stomach and vagina kill pathogens

non pathogenic bacteria live in our digestive/ genital tract and compete with invading organisms

ear canal lined with wax

vomiting and diarrhoea expel contents of gut along with any infective pathogens

Question 35

what types of defence is blood clotting?

Why is it needed?

Why is the process so complex?

How is it activated?

What is involved?

Name the order of enzymes:

Answer 35

• second line non specific
• Blood clotting is required to provide a temporary seal to prevent infection as if skin is breached pathogens can enter the body
• to avoid clotting where its not needed
• When platelets come into contact with collagen in skin or wall of damaged blood vessel they adhere and begin to secreted several substances
• clotting factors which activate an enzyme cascade (product of one reaction activates the next)
• Thromboplastin converts inactive protease to active protease. Ca2+ catalyst helps prothrombin convert to thrombin which converts soluble fibrinogen to insoluble fibrin. This forms a clot with traps platelets and blood cells, then dries to form a scab.

Question 36

Apart from the thromoplastin cascade, what is the other clotting method?

Answer 36

serotonin makes the smooth muscle in the walls of the blood vessels contract so they narrow and reduce the supply of blood to the area

Question 37

What is the second stage of wound repair?

Answer 37

• layer of fibrous collagen starts to form under the scab to give new tissue strength
• granulation tissue fills the would allowing further changes to occur underneath
• The outer layers of stem epidermal cells divide by mitosis, into skin cells and migrate to the edge of the wound.
• Platelets secrete growth factors that attract cells to divide and grow
• The tissue then contracts to draw the edges of the wound together
• new blood vessels form to supply nutrients to the tissue
• death of unwanted cells
• scab falls of once new epidermis reaches normal thickness

Question 38

Secondary defences

Answer 38

phagocytic and antimicrobial cells that act against the type of microorganism that has breeched the primary defences non specific

Question 39

inflammation definition What are the signs?

Answer 39

the local response to tissue damage and infection, involving the release of chemical signalling molecules and resulting in an increased blood flow and movement of phagocytes into the infected tissue swelling (oedema), pain, heat and redness

Question 40

Inflammation process

Answer 40

• Damaged/infected tissue releases histamine molecules from mast cells which increase permeability of blood capillaries.
• Fluid leaks into surrounding tissue fluid which is what causes swelling and pain and phagocytes can leave the blood and enter infected tissues.
• The histamine also cause vasodilation which makes the area hot and brings lots of white blood cells. The raised temperature also helps prevent pathogens reproducing.
• When excess tissue drains into lymphatic system the specific immune response is initiated
• Histamine stimulate infected cells to secrete cytokines. Cytokines (including interleukin) stimulate defences in affected area including binding proteins to material to be digested by phagocytes (these proteins can increase 1000x at the start of an infection!). They also promote inflammation and cause the liver to release acute phase proteins, some of which bind to the surfaces of bacteria and damaged host cells to promote phagocytosis. These signalling molecules are also responsible for causing fever and sleepiness by stimulating the brain

Question 41

Fever- how does it occur Why is it good?

Answer 41

hypothalamus in brain maintains 37*C. when a pathogen invades, cytokine stimulate the hypothalamus to reset the thermostat and temperature goes up. This inhibits pathogen reproduction and the specific immune system works faster at higher temperatures.

Question 42

What is a passive defence?

What are the passive plant defences- split into physical and chemical?

Answer 42

there all the time

Physical:

1. waxy cuticle over leaf epidermis- stops virus and bacteria entering through wounds made by herbivores
2. Casparian strip in root endodermis- stops fungi entering through roots
3. bark
4. cellulose cell walls
5. stomatal closure

Chemical:

1. secreting toxic compounds- phenols
2. secreting enzyme inhibitors that inhibit enzymes needed for plants to enter the plant- tannins
3. Sticky resins in bark prevent spread
4. secreting compounds which support growth of microorgainsims that are competitors of pathogens
5. receptor molecules on cell surface membranes detect pathogens and activate plant defences

Question 43

Active plant defences

Answer 43

1. Hypersensitivity/ necrosis Immediate death of tissue surrounding infection site to prevent spread of infection. Many pathogens require a living host tissue to survive for energy and nutrients used for growth
2. Callose deposition Callose is a large polysaccharide that blocks sieve tubes (phloem) or plasmodesmata preventing the spread of the pathogen. Also deposited in sieve pores to block the transport of phloem sap and impede pathogen movement. Cells walls have it too, along with antimicrobial compounds like hydrogen peroxide
3. Tyloses growths that block the xylem by swelling preventing pathogen spreading through plant. they are filled with plant chemicals called terpenes
4. Cell signalling using signalling molecules like salicylic acid activate defence mechanisms in uninfected areas. They then have system acquired resistance for some time after the original infection if it returns. They produce defence chemicals- phytoalexins which:

disrupt cell surface membranes of bacteria

delay reproduction of pathogen

disrupt metabolism of pathogen

release chitinases to break down hyphae walls

Question 44

Name a few plant chemicals we extract for use:

Why can’t plants produce cells that roam all over the body?

Answer 44

insect repellents- citronella from lemon grass

insecticides- caffeine is toxin to insects and fungi

fixed cell walls

Question 45

What are phagocytes?

What are 3 phagocytes?

when and where are they produced?

what causes them to migrate?

what do they contain

Answer 45

specialised cells in the blood and tissue which engulf and digest pathogens and dead cells

neutrophils macrophages (monocytes) dendritic cells

throughout life by the bone marrow

signalling molecules from damaged cells

lysosomes (vesicle containing digestive enzymes)

Question 46

What is the most common phagocyte?

what is a special feature of this phagocyte and why is it useful?

what happens during infections? What happens after they ingest bacteria? What is pus mostly made of?

Answer 46

neutrophil

lobed nucleus so they can leave capillary walls as more flexible

travel in blood and enter tissue fluid during infections, large numbers quickly released from bone barrow in infections

short lived- die after ingesting bacteria

dead neutrophils

Question 47

What do macrophages do?

How are they different to neutrophils?

Where are they found?

where are they made?

Answer 47

consume and destroy any pathogens they encounter

larger and long lived, and initiate a specific immune response as they display antigens from the pathogens to lymphocytes

found in organs/ lymph not the blood. common in lungs as stuff enters there

bone marrow as monocytes (called macrophages once reach organs)

Question 48

What is a special feature of dendritic cells?

where are they found?

what happens to them after phagocytosis?

Answer 48

have long processes to give a large surface area to interact with pathogens and lymphocytes and are antigen presenting cells (APC’s) like macrophages?

mainly found in areas near to surfaces like skin, digestive tract, mucous membranes

they migrate to the lymph nodes

Question 49

Describe the process of phagocytosis include process of antigen presentation

Answer 49

1. chemotaxis (phagocyte moves in response to chemicals produced by pathogens) and adherence of microbe to phagocyte. can recognise non human proteins on pathogen (not specific)
2. ingestion of microbe to phagocyte by endocytosis and invagination
3. formation of a phagosome (phagocytic vesicle)
4. formation of a phagolysosome ( when lysosome fuses with phagosome)
5. digestion of ingested microbe by enzymes from lysosome
6. formation of residual body containing indigestible material
7. discharge of waste materials my exocytosis and antigens from surface of pathogen absorbed so they can be displayed and used to tell lymphocytes which antibodies to make much quicker, without the real pathogen there to cause damage. The antigens from the pathogen surface membrane combine with special glycoproteins from cytoplasm called major hostocompatability complex (MHC) which moves them to the phagocyte surface membrane becoming APC

Question 50

How does histamine increase effectiveness of phagocytes?

Answer 50

when cells are under attack they release histamine which makes capillaries more leaky so extra fluid in the blood leaves to become tissue fluid this means more fluid enters the lymphatic system, flushing pathogens towards the macrophages waiting in the lymph nodes so the specific immune response can begin sooner

Question 51

When are cytokines released and how do they help phagocytes?

what do opsonins do and how do they help?

Answer 51

cytokines are released by a pathogen when it engulfs the phagocyte and they tell other phagocytes the body is under attack and stimulate them to move to the site of the infection

opsonins are chemicals eg. antibodies that bind to and tag the pathogen making it more easily recognised by the phagocyte they also bind to receptors on phagocytes membranes which help the pathogen be engulfed

Question 52

3 features of antigens:

What do they do?

What are they specific to?

what is specific to antigens?

Answer 52

1. proteins or glycoproteins
2. large molecules
3. have a specific shape on or in the cell surface membrane

they stimulate a immune response eg. production of antibodies

the organism

antibodies

Question 53

What is another name for antibodies?

what produces them?

what structure do they have?

Answer 53

immunoglobulins

lymphocytes in response to an infection

globular proteins with 4 or more polypeptides

Question 54

In the antibody structure: what is the function of the variable region?

What is the function of the hinge region?

what is the function of the constant region?

What are the light chains?

What are the heavy chains?

Where is the antigen binding site?

What bonds are involved?

Answer 54

it changes due to different sequence of aa giving it a different 3D shape so is specific for different antibodies

allows flexibility so the antibody can bind to 2 separate antigens

its the same for all antibodies of the same class, and is a receptor binding site on the phagocyte surface so it can detect pathogens labelled by antibodies for phagocytosis

2 smaller polypeptides on the outside

2 larger polypeptides on the inside

at the top of the y and involves all 4 polypeptides- there are 2 identical ones

disulphide bridges form between polypeptides and within polypeptides

Question 55

What is it called when the antigen and antibody bind?

Answer 55

antigen-antibody complex

Question 56

How do antibodies work?

Answer 56

Agglutination- antibodies bind to 2 identical antigens on 2 or more pathogens which makes them clump together so they are less likely to spread and and easier for engulfing. bigger antigens are better for this as there are more binding sites

Immobilisation- some attach to the bacterial flagella making them less active and easier for phagocytes to engulf

Opsonins- some act as these by acting as labels coating the pathogen so the phagocyte can identify it. The phagocytes have receptors for the constant region of antibodies

Some block the binding sites on the pathogen so its unable to bind to a host cell (neutralisation)

Antitoxins- they block toxins they are complementary to them so combine with them to make them harmless eg, for those causing diphtheria and tetanus

They also can attach to the membrane and puncture or burst it

Question 57

Describe trend in graph and explain why for primary and secondary response

Answer 57

low numbers of antibodies in blood as there is a lag phase until antibodies are produced.

small and gradual peak which is short lived.

if the first infection passes the antibody concentration required for immunity then if a second infection occurs with the same pathogen the lymphocytes can quickly make the same antibodies again- the previous ones don’t stay in the blood.

immediate and stronger response shown by a steeper and higher peak.

Due to the presence of memory cells made during the response it is long lived. The graph declines slower too why long lived due to memory cells??

Question 58

What is the specific immune system?

Answer 58

when lymphocytes and antibodies act against specific pathogens

Question 59

What is the difference between the specific and no specific immune system?

Answer 59

specific is much slower as only have a small no of each as there are so many lymphocytes so there is a lag time between being infected and producing antibodies due to clonal selection and expansion

also not born with it but can produce when there’s an infection

Question 60

Immune response

Answer 60

the sequence of events that occur as the specific immune system responds to foreign antigens involving activation of cloning of B cells and T cells specific to antigens

Question 61

Where do B and T cells originate and mature?

Answer 61

stem cells in bone marrow where they differentiate into mature cells that spread out through the body’s lymphatic system in bone marrow but migrate to thymus gland to mature then spread across lymphatic system

Question 62

What types of T cells are there?

What types of B cells are there?

Answer 62

T helper cells

T killer cells

T memory cells

T regulator cells

Plasma cells

B memory cells

Question 63

What do T helper cells do?

Answer 63

have CD4 receptors on cell surface membranes which bind to surface of antigens on APC’s

produce interleukins when they bind- interleukin 1 produced by macrophage which enhances T cell activation, and T cell releases interleukin 2 which causes the proliferation of other helper T cells (positive feedback) and helps activate plasma cells and T killer cells

interferon may also be produced stimulating killer T cell activity

Question 64

What do killer T cells do?

Answer 64

destroy pathogens and infected cells (they display antigens on surface)

produce chemical perforin which has proteins that channel through membranes so toxins can enter, killing the pathogen

Question 65

What do T memory cells do?

Answer 65

part of immunological memory

have encountered specific antigens before so can respond quickly and strongly if that antigen is encountered again by dividing to form killer T cells

Question 66

What do T regulator cells do?

Answer 66

control the immune system by stopping the immune response when no more antigens are present

they also make sure the body recognises self antigens so doesn’t set up an autoimmune response

Question 67

What do B lymphocytes do?

Answer 67

produce antibodies to a particular antigen which inactivate circulating antigens

only live for a few days but produce 2,000 antibodies/ second

Question 68

What do B memory cells do?

Answer 68

live for a very long time and provide immunological memory

remember a very specific antigen and if its encountered again they can rapidly differentiate into plasma cells

more antibodies are produced and they last longer

Question 69

What types of immunity are there?

Answer 69

Active: natural and artificial. involves an immune response, long term but takes a long time for enough B and T cells to be produced for an effective response

Passive: Natural and artificial. no contact with antigen, no immune response, quick

Question 70

Describe the types of active immunity:

Answer 70

Natural:

• Acquired due to infection When you meet a pathogen your immune system is activated and antibodies are formed to destroy antigens.
• T and B memory cells are produced so if you meet the pathogen again your immune system recognises the antigen it can immediately destroy the pathogen before it causes symptoms
• Active as body has acted itself to produce antibodies/ memory cells

Artificial:

• Some diseases will kill us before the immune system makes the antibodies they need so medical science can give us immunity without any live pathogen contact A vaccine gives the antibody an antigen through an injection into the bloodstream so the body is stimulated to make its own antibodies and memory cells- primary immune response
• The antigen is either dead, inactivated, weakened, genetically engineered, toxin molecules detoxified
• Then if you come into contact with a live pathogen the secondary immune response is triggered and the pathogen is rapidly destroyed before get symptoms so you have long term immunity
• they can also be used in an epidemic to prevent the spread of a communicable disease

Question 71

Describe the types of passive immunity:

Answer 71

Natural:

• The immune system of a new born baby isn’t mature and can’t make antibodies for the first couple of months. To protect itself, some antibodies cross the placenta from mother to foetus in uterus
• Colostrum is the first milk a mammalian mother makes with lots of IgA antibodies
• The infant gut allows these glycoproteins to pass into the bloodstream without being digested so within a few days of birth a breast fed baby will have the same level of antibody protection against the disease as mother
• Lasts until the immune system can make its own antibodies Only against disease the mother had but usually from environment baby will live in

​Artificial:

• For potentially fatal diseases, antibodies are formed in 1 individual, extracted and injected into the bloodstream of another
• Gives temporary immunity but instantly prevents development of disease

Question 72

What is an autoimmune disease?

Why does it occur?

What is the downside to the treatment?

Answer 72

When the immune system stops recognising self cells and starts to attack healthy body tissue

May be because immune system responds abnormally to mild pathogen or normal body microorganisms, or T regulator cells don’t work effectively

Immunosuppressants prevent the immune system working so has less defence against communicable diseases

Question 73

What are the areas affected, symptoms and treatments for rheumatoid arthrits?

Answer 73

affects the joints, starting with fingers and hands, ankles and feet then progressing to shoulders etc.

constant pain and muscle spasms, tendons become inflamed and people become lethargic

no cure, but anti-inflammatory drugs, steroids, immunosuppressants and pain relief

Question 74

What are the areas affected, symptoms and treatments for lupus (systemic lupus erythematosus- SLE)

Answer 74

skin and joints, and specific organs like the heart, lungs, kidney, liver, brain

different each time it flares up, butterfly rash across face, joint pain, fatigue

no cure but treatment involves anti-inflammatory drugs, steroids, immunosuppressants

Question 75

What are the areas affected, symptoms and treatments for multiple sclerosis?

Answer 75

affects neurons, cells of brain and spinal cord

fatigue, pain, bladder and bowel issues, sexual disfunction, movement and coordination problems visual problems, cognition and emotional changes

symptomatic treatments- pain killers

therapies- CBT, physio

management techniques- pace so manage fatigue

rehab and aid equipment for day to day living

Question 76

Herd vaccination

Ring vaccination

Answer 76

• where everyone possible gets vaccinated which protects those who don’t have immunity so there is less chance of an outbreak as its hard to spread.
• This helps people who are unable to be vaccinated like immunocompromised as they have low chance of coming into contact with the disease
• vaccinating only those who are most likely to be infected like those who live or work near an infected person or their contacts to prevent them catching and spreading it/ vulnerable

Question 77

Why are vaccines necessary

Answer 77

even though many of the diseases are very rare in the UK, they still exist in the world and could be introduced by travellers from areas where there is still endemic

Question 78

What are the problems with vaccines?

Answer 78

1. hard to get them against eukaryotic organisms as because they have many genes that code for cell surface antigens, which change as it passes through the body becoming different strains eg. Plasmodium. It also remains inside the liver and red blood cells where antibodies have no effect. They do this by: Antigenic drift- small changes in structure and shape of antigens within the same strain of virus Antigenic shift- major changes in antigens within the same strain cross breeding- different strains of viruses invading the same cell, with the formation of new viruses with antigens from different strains When this happens, new vaccines must be made as no one will have immunity to this strain, and if there was. pandemic then stocks would struggle to cope

2. small risk of side effects and complications, swell as false news like MMR and autism mean people dont want vaccines and puts risk to herd immunity and those who aren’t vaccinated

3. People used to be compelled by law but protests over the compulsory smallpox vaccination saw this dropped

4. Historically prisoners and mental institution patients were used to trail vaccines but that is no longer occurring. However, children need to be in the subject population, to test vaccines during and beyond childhood which brings issue of informed consent. in developing countries this can be a problem where cultural and social differences may interfere with effective communication of research aims and key terms may be lost in translation, whilst regulatory boards may not be experienced to protect population from exploitation

5. Vaccines needed for developing countries may be considered low priority in developed countries as won’t make money. developing countries also trial vaccines putting themselves at risk for a vaccine they dot need and which is used in developing nations

Question 79

Cell mediated immunity

Answer 79

• non specific defence system
• macrophages engulf and digest pathogens in phagocytosis forming APC’s
• The receptors on some of the T helper cells fit the antigens which activates them to produce interleukins etc. (clonal selection)
• interleukins cause more T cells to divide my mitosis producing clones and they may develop into T memory cells, producing interleukins that stimulate phagocytosis and stimulate B cells to divide into plasma cells and stimulate the development of clones of killer T cells specific to the presented antigen so they can destroy infected cells (clonal expansion)
• T cells also recognise antigen fragments presented by infected cells

Question 80

Humoral immunity

Answer 80

• Responds to antigens found outside cells so produces antibodies that are soluble in the blood and tissue fluid and not attached to cells?? when are they?
• B lymphocytes have antibodies on their cell surface membrane and each b lymphocyte has different antibodies
• A pathogen carry’s specific antigens or produces toxins that act as antigens and the complementary B cell antibodies bind (clonal selection)
• The B cell engulfs and processes the antigens to become an APC???. Then an activated T helper cell binds to the B cell APC selecting the B cell for cloning??
• The B cell then divides by mitosis to give clones of plasma cells and memory cells (clonal expansion)
• Plasma cells then produce antibodies that fit the specific antigen which is the primary immune response- can take a while which is when we get symptoms
• Secondary immune response is by memory cells

Question 81

What is biodiversity?

What are the three levels it can be studied at?

Answer 81

the variety of living organisms present in an area

Habitat biodiversity

species biodiversity

genetic biodiversity

Question 82

What is a habitat?

What is habitat biodiversity and how does it affect species?

What places have large habitat biodiversity in UK?

Where has lower?

What does habitat biodiversity provide?

Why can it be hard to measure?

NICHE-

Answer 82

• a place where species live
• The number of different habitats found in an area. each habitat can support a number of different species so more habitat biodiversity means greater species biodiversity
• Meadow, woodland, river, sand dune Farmed
• countryside has lower as only one crop
• resources organisms need to survive like light, CO2, water, mineral ions, food, water, shelter and somewhere to breed
• lots of species feed in 1 ecosystem and roost in another or are seasonal
• role of a species in an ecosystem, like the position in the food web or how it interacts with factors in the environment

Question 83

What does species diversity involve?

Answer 83

species richness- the number of different species living in a particular area species

evenness- number of individuals of each species living in a community

Question 84

What is genetic biodiversity?

What is a gene pool?

What are alloenzymes and what do they affect?

When is genetic diversity limited and why?

What problems does this cause?

Answer 84

• the variety of genes that make up a species. For some genes they are the same for all individuals within a species but some have different alleles (different versions)
• Gene pool consists of all the alleles of all the genes within a species
• different forms of an enzyme that have different primary sequences because of different alleles on the genes coding for the enzymes . This can sometimes have an affect on phenotype. Alleles have different nucleotide sequences leading to different amino acids.
• in small populations because inbreeding leads to homozygous genes.
• genes caused by recessive alleles are then more common

Question 85

What factors affect biodiversity?

Answer 85

Population growth due to improvements in medicine, hygiene, housing and infrastructure allowing people to live longer (habitat loss, overexploitation)

Agriculture

Climate change

Question 86

What causes habitat loss?

What is the land used for?

What are the negative affects?

Answer 86

Due to deforestation and urbanisation, forest fires and acid rain. marine habitat loss is due to dynamiting coral reefs (extreme way to catch fish), trawl nets pulled across ocean floor and dredging of coastal waters, pollution from rivers full of sediment due to runoff from roads, urban areas and removed trees losing sediment and development along the coast

cleaning land for agriculture, industry, housing, transport, leisure water storage and waste disposal

• causes habitat fragmentation which can cause inbreeding and local extinction
• flooding and soil erosion which looses nutrients
• reduces number of trees present in an area and if 1 type of tree is felled the species diversity is reduced
• reduced number of animal species present as their habitats are destroyed, and food source. This has a ripple effect through the food chain and may also cause them to migrate
• replanting of trees is not as effective as only commercially available trees are used
• coral reefs are also damaged

Question 87

Examples of overexploitation:

Answer 87

• trees are felled at a faster rate than they can regenerate especially slow growing hardwoods like teak and mahogany
• fish stocks are also overexploited like Atlantic cod which have failed to recover from the 1990’s even after no further fishing. When large predatory fish like cod are removed, less food is available for larger fish, marine animals and seabirds further reducing biodiversity
• in poorer parts of the world, wild animals are overexploited as roads for logging provide easy access for hunting bush meat, especially monkeys
• plants can also be overexploited like hunting as food or to sell

Question 88

How does agriculture lower biodiversity and what negative affects does this have?

Answer 88

• monoculture is the production of 1 crop only which really lowers biodiversity and few animals will be supported EG. palm oil plantations and livestock farming top feed the growing population
• pests are more common because there is an unlimited supply of food so more chemicals are needed to maximise food production
• deforestation to increase land available for growing crops or rearing animals
• removal of hedgerows due to mechanisation as it allows them to use big machines to plant, fertilise an harvest crops and create more land. Hedgerows are habitats for many species like blackbirds, hedgehogs and mice
• agrochemicals like pesticides to kill pests, however they may also kill non target species and the insect pests are pollinators so important in the habitat and may be a food source for other organisms.
• herbicides kill weeds which compete with crops for light, minerals and water but can also kill non target species. however killing them reduces plant biodiversity and animal biodiversity by removing their food source.
• Fertilisers are needed because of intensive farming but encourage growth of plants which can limit light for lower growing species
• chemicals can pollute rivers as rain washes them in, causing eutrophication. This is when nutrients like nitrate and phosphate ions are too high so more frequent algae blooms which block sunlight so less photosynthesis and plants die. they can also cause large growths of plankton which quickly die and are consumed by bacteria depleting the waters of oxygen, as does age blooms which kills fish.
• Land drainage causes soil invertebrates to live deeper in the soil so less accessible to birds and mammals

Question 89

What is the trend in global warming?

What aspects of global warming are there?

Answer 89

warming trend in last 50 years is nearly 2x larger than previous 100 years

water vapour levels have increased since 1980’s due to warmer air and more precipitation and more extreme weather

ocean is expanding as it has been absorbing over 80% of the heat added to the climate system

1.8mm/yr from 1961-2003 sea level rise also caused by glacier and ice cap melt due to increasing arctic temperatures CO2 levels increase, trapping thermal energy and acidifying oceans

Question 90

How does global warming affect biodiversity?

Answer 90

• melting of polar ice caps could lead to extinction of plants and animals species eg. algae is on the underside of ice is a producer for birds and marine animals.
• Some species are moving further north from the arctic to find the conditions they want where they may have to compete for survival
• rising sea levels can cause floods which reduces terrestrial habitats, and salt water can flow further up fresh rivers which reduces habitats of fresh water species
• High temperatures and less rain mean plants can die so rough resistant ones become dominant.
• Animal species dependent on plant species would suffer and new animal species invade
• Insect life cycles and populations change as they adapt to climate change will affect plants as they are key pollinators. Plants may go extinct. Insects carry plant and animal pathogens so could spread tropical diseases to poles
• decrease in pH due to CO2 dissolving makes it harder for organisms to make shells of calcium carbonate which acts as a sink for carbon so less long term stores of carbon
• stratification is when surface waters don’t mix with nutrient rich water deep in the ocean due to warming so phytoplankton won’t grow and divide to produce for the oceans

Question 91

Positive about climate change

Answer 91

1. if climate change is slow species can adapt by migration or finding a new food source.
2. You may loose nature species but would gain new ones so no biodiversity lost even though species mix changes

however climate change is occurring much faster than before

Question 92

Ecological reasons for maintaining biodiversity

Answer 92

interdependence of organisms- removal of one species may affect others through a food source or habitat

keystone species- play and important role in maintaining the structure of a community compared to their size or number so need to be protected to avoid drastic change in a habitat and keep it stable whilst maintaining biodiversity. They can be top/ apex predators or not

Gene pool- higher biodiversity means higher stability in the ecosystems so can withstand environmental change like storms better and recover better. They become unstable due to loss of populations at different trophic levels eg. loss of top predators like lions causes increase in herbivores so overgrazing and erosion and loss of biodiversity

Question 93

Economic reasons for maintaining biodiversity: agricultural

Answer 93

soil erosion and loss of nutrients and desertification caused by deforestation reduces the countries ability to grow crops and feed its people so they rely on other countries.

monoculture also causes soil depletion as crops are harvested so nutrients aren’t replenished and crops become weaker and more vulnerable to pests so chemicals are used to maintain productivity. rotting material also helps bind soil

high biodiversity provides protection against abiotic stresses like extreme weather so a change in conditions don’t destroy whole crops EG Irish potato famine only relied on 2 varieties of potato.

plant varieties needed for cross breeding so get better disease resistance or increased yield characteristics so less land needed

Question 94

Economic reasons for maintaining biodiversity: materials

Answer 94

food - hardwood timber is an important resource but removed unsustainably which will result in the collapse of an industry in an area as it will no longer be economically viable

undiscovered species in tropical rainforests may have chemical or medical uses so biodiversity loss causes them to go extinct and they would have had economic importance

when habitats are destroyed so are populations of commonly grown plants and without genetic diversity, plant breeders struggle to breed to new varieties reducing horticultural industry income

Question 95

Economic reasons for maintaining biodiversity: services

Answer 95

• plants transpire water passing to the water cycle which gives us drinking water. they also filter it through the soil and rock and organic waste material in water is broken down in water is broken down
• nutrient cycling maintains soil fertility
• reefs and mangroves protect from erosion
• habitats moderate floods, droughts and extremes of wind and temperature
• insects pollinate crops
• forests and peat bogs absorb CO2

Question 96

Aesthetic reasons for maintaining biodiversity

Answer 96

health and well being- patients recover quicker from stress and injury when in natural environment and helps everyday people relax and enrich their lives

attractive environment- inspires musicians and writers who provide pleasure for readers so landscapes must be protected economic for tourism like ecotourism

Question 97

What are the methods of maintaining biodiversity in situ?

Answer 97

1. internationally designated areas
2. nationally protected areas
3. nature reserves
4. marine conservation zones

Question 98

What is in situ conservation?

Why is it preferred?

Why may it not be good?

Answer 98

conservation of species in its natural habitat

• preferred option as have all the resources they need
• are adapted to their environment
• continue to evolve in their natural environment
• help interdependent species
• larger species have more space
• animals more likely to breed if in natural environment
• if populations are small they risk poaching

Question 99

Wildlife reserves

Answer 99

internationally designated areas: designated by organisations like UNESCO. 28 world heritage sites in UK (important physical or cultural sites) and 5 biosphere reserves promoting sustainable development and preventing hunting etc.

Nationally protected areas like national parks- 15 in England, Scotland and Wales with separate authority for each. Also areas of outstanding natural beauty- 46 in England, Wales and N Ireland

nature reserves can be national and protect sensitive ecosystems and provide outdoor labs for research administered by natural England to maintain conditions for rarest species

local nature reserves under control of local authorities through ownership or lease with landowner and are for natural species

sites of special scientific interest give legal protection to the best sites for wildlife and geology so landowners can’t change the management of the are without permission

Question 100

Marine conservation zones

Answer 100

• marine and coastal access act 2009 set up these 28 zones
• they include refuge areas where fish populations can build up
• also protect the habitats
• ban commercial fishing zones
• can turn an area devoid of life to support a diverse community

Question 101

What are some other general ways of maintaining biodiversity?

Answer 101

controlled grazing- particular area or amount of time so can recover

restricting human access- no beach access in seal reproductive season, paths

controlled poaching- defences to prevent access, fines, remove rhino horns

feeding animals- help them survive to reproductive age

reintroduction of species- if locally extinct or in low numbers

remove invasive species- they compete for resources

halting succession- so doesn’t become woodland by controlled grazing which eat seedlings

create new habitats- digging ponds, sinking ships for coral to colonise

Question 102

Ex situ conservation examples

what is it?

why is it needed?

Answer 102

botanical gardens, seed banks and zoos

removal of species from wild to a protected place

necessary due to mining, road construction, development, grazing, logging and poaching. May not be able to conserve in natural habitat as its shrinking and fragmented

Question 103

Botanical gardens

Answer 103

• grow plants that are extinct in the wild hoping they can be reintroduced
• they are given all the resources they need
• protect populations of plants collected from wild so there’s enough for people to buy so they don’t have to take endangered from wild
• researching methods of growth and reproduction so can be grown in appropriate conditions
• researching conservation methods so can be reintroduced
• used to educate public of role of plants in ecosystems and economic value

Question 104

What are seed banks?

How are the seeds collected and stored?

What are they used for?

What happens if the seeds can’t be stored?

Answer 104

A gene bank where seeds are stored so new plants can be grown in the future and are stores of genetic diversity

Collected from the wild or crops, sorted, dried to slow metabolism and reduce ice crystal damage and stored at very cold temperatures. They are checked at 5 yr intervals to see if their still viable by attempting to germinate them. They remain viable for centuries as it slows down the rate they loose their ability to germinate

• Used for future breeding programmes
• To genetically modify plants for economic gain
• A store of material for medicines
• To prevent extinction

some can’t be stored so can be kept as tissue cultures or grown as mature plants in fieldworker gene banks

Question 105

What do zoos do?

How do they maintain diversity?

Answer 105

1. protect endangered and vulnerable species
2. research biology of species to gain a better understanding of breeding habitats and habitat requirements
3. contribute to reintroduction schemes
4. educate public about wildlife and conservation

frozen

• can hold a lot of genetic diversity for a long time and include frozen eggs
• can be damaged due to ice crystals which damage internal membranes

captive breeding programmes

• provides animals shelter, food, no predators and veterinary treatment before release
• may not be able to survive as have no resistance to local disease
• have behaviour issue, don’t know how to hunt for food (try to hide it in cages).
• The genetic population of captive may be so different to original they can’t interbreed
• natural habitat may be destroyed or not big enough to support more individuals
• to avoid small gene pools they exchange specimens or use artificial insemination from frozen sperm banks and take part in breeding programmes to prevent inbreeding

Question 106

International union for the conservation of nature

Answer 106

• Assess the status of world animal and plant species as animals don’t respect countries boundaries so international cooperation is needed
• once a year they publish a red list detailing current status of threatened animals
• They also established CITES

Question 107

Conservation agreements

Answer 107

ICUN

CBD

CITES

CSS

Question 108

What does CBD stand for?

What does it do?

Answer 108

1992 rio conventions biological diversity meeting of 172 nations

1. earths summit ensured national strategies for sustainable development to maintain biodiversity
2. convention of climate change to stabilise greenhouse gas concentrations
3. conservation to combat desertification by reducing effect of drought

Question 109

What does CITES stand for

What does it do?

What are the disadvantages?

Answer 109

convention of international trade in endangered species- 1973 145 countries signed the agreement. 35,000 species protected

1. regulates international trade of endangered species to prevent over exploitation eg. pet trade and materials like ivory which is illegal
2. has 3 appendix depending on how at risk of extinction species are

• if trade is illegal, price increases so its more worthwhile to break the law
• trade spikes when new species are announced to go on the list eg. poaching of elephants as increased as illegal trade of ivory increases in response to demand from china

Question 110

What are local countryside stewardship schemes?

What do they do?

Answer 110

in England it operated 1991-2014 involved payments from governments to farmers to make conservation a part of normal practice. now replaced by similar environmental stewardship scheme

1. ensure land is well managed
2. retains traditional character
3. protect historic features and natural resources
4. improve and create new habitats
5. resort neglected land
6. conserve traditional livestock and crops
7. have opportunities for people to visit and learn about the countryside

Question 111

classification

taxonomy

phylogeny

Answer 111

the process of sorting living things into groups

the study of the principles of classification

the study of the evolutionary relationships between organisms often presented as a phylogenetic tree which shows how different species have evolved from a common ancestor, with earliest at base and newests at tips. Based on physical characteristics as used to only be able to see external and internal (microscope) and genetic makeup. 2 groups that branch from the same node (branch) are sister groups. linen classification uses phylogeny

Question 112

Why do we classify?

Answer 112

• convenience, makes studying living organisms more manageable
• makes it easier to identify organisms both new and old
• helps us see interspecies relationships
• creates a world wide record of all living organisms
• helps communication worldwide to share research
• see evolutionary links as species in the same group probably share characteristics as they have evolved from common ancestors

Question 113

How do we classify?

Answer 113

• historically it has been based on observable features
• more recently it has been on DNA and biochemistry- molecular biology because if characteristics change so must the proteins and so much the DNA which codes for them

Question 114

What did carl Linnaeus found?

Answer 114

the binomial system of nomenclature and the hierarchal system of classification which is largely based on observable features which represent evolutionary relationships

Question 115

What are the taxonomic groups in the hierarchal system?

Answer 115

Kingdom: largest group of organisms sharing common features

Phylum: major subdivision of a Kingdom

Class: group of related orders, subdivision of phylum

Order: group of related families, subdivision of a class

Family: group of closely related genera, subdivision of order

Genus: group of related species, subdivision of family

Species: breed freely with one another. smallest group and most specific/ least diversity

Question 116

What do you need to remember about binomial nomenclature?

Answer 116

1. Genus and species
2. Only G capital letter
3. italics or underline if handwritten

Question 117

species

what is not a species?

Answer 117

• the smallest basic taxonomic unit used to define living organisms
• a group of individuals with similar key features but show variation and can interbreed and produce fertile offspring (doesn’t take into account simple organisms that reproduce asexually)

1. mule from a male donkey and a female horse
2. hinny from male horse and female donkey can’t produce fertile offspring

Question 118

Are you more related if your species or genus are the same?

How do you find the most closely related species on a phylogenetic tree?

Answer 118

genus

doesn’t matter which direction, but closest branch

Question 119

What are the advantages of phylogeny?

Answer 119

produces a continuous tree whereas classification requires discrete taxonomic groups so scientists don’t have to put organisms into a specific group if they dont quite fit in heirachal structure

Linnean classification can be misleading as it implies different groups in the same rank are equivalent, whereas in reality they may have longer history, different levels of diversity so aren’t comparable

Question 120

Homology

Answer 120

shared features that are inherited from a common ancestor but may not be used for same function

eg bats wings and human arms have same bone pattern so are homologous but are used in different ways

The more recently 2 species shared a common ancestor the more homologies they will have and the more similar those homologies will be

divergent

Question 121

Using antibodies for molecular evidence in classification

Answer 121

• Antibodies to a specific antigen can be produced by injecting an animal with that antigen.
• Their blood is taken a week later and prepared as an antiserum by removing all cells and adding anticlotting agent. The antiserum contains antibodies from the plasma cells.
• The serum can then be used to test the blood of other species to see if they same antigen is present

Can be done by spinning human blood in a centrifuge to remove red and white blood cells then treating for clotting. Sample of plasma is injected into mouse and then later a sample of blood is taken from the mouse. The antiserum conaytins antibodies against all proteins in human blood plasma. So when combined with blood, they would attatch to human antigens and precipitate. The degree of precipitation is compared to mouse antibodies and human blood plasma.

Question 122

Using DNA sequencing for molecular evidence in classification

Answer 122

• Sequence of amino acids is determined by sequence of bases in genes that code for them.
• Its easier to sequence DNA than proteins, and its more detailed and specific due to the degenerative nature of the code. May get silent mutations- changes in base pairs still result in same amino acid.
• Neutral mutations change the amino acid but not the R group, so they don’t affect function.
• Protein sequences are determined from DNA sequnces now.
• Genes that code for rRNA change slowly so are useful in sorting out relationships between higher taxa like domains, kingdoms and phyla.
• Rapidly changing genes show relationships between species and even between isolated populations of species.
• DNA is also more stable than a protein so can sequence DNA from extinct organisms.
• Most useful genes to analyse are the genes that code for proteins required for fundamental features all organisms have.

Question 123

Using protein sequencing for molecular evidence in classification

Answer 123

Comparing sequences of amino acids.

The sequences are created from a 1 letter code.

Tree diagrams can be drawn, with the lengths of branches proporinal to number of differences in primary sequence.

Question 124

Using DNA hybridisation for molecular evidence in classification

Answer 124

1. Each DNA molecule is made of 2 strands of nucleotides and heating to around 90*C the DNA molecules causes the hydrogen bonds to break between them.
2. The strands separate and can be isolated. Two species can then have their single stranded DNA mixed.
3. When cooled, the attraction of the nucelotides will make the hydrogen bonds reform.
4. As there are genetic differences, the match between the 2 strands is not perfect and the hydrogen bonding will be weaker, so can be broken with little heat.
5. The closer the match the more heat required to break the strands.

Question 125

How has molecular evidence changed classification?

Answer 125

Used to use anatomy, morphology, behaviour, physiology and cell structure

now can study sequences of amino acids in proteins and the sequence of nucleotides in DNA- molecular phylogeny

Question 126

Features of the 5 kingdoms

Answer 126

Question 127

Sources of medicines

example of plant and microorganism based medicines

Answer 127

• complex computer programmes can design new drugs
• many commonly used drugs come from plants and microorgaisms

1. Penicillin (mould) is an antibiotic
2. Aspirin (willowbark) is a painkiller, anticoagulent, antiinflammatory
3. digoxin (foxgloves) for heart failure
4. vancomycin (soil fungus) most powerful antibiotic

Question 128

Personalised medicine

Why does it work?

how can it be used?

example

What is pharmacogenomics?

Answer 128

the combination of drugs that work with your individual combination of genetics and disease

people have different genes so produce different enzymes and proteins so certain medicines are more effective on some poeple than others

by testing someones genome its possible to identify the effectiveness of drugs so they are mre precise and have less side effects

EG. HER2 gene mutation for trastuzumab

interweaving knowlege of drug actions with personalised genetic material

Question 129

Why is synthetic biology needed?

What 2 ways can it be useed

examples

Answer 129

some drugs are difficult or expensive to produce

genetic engirneering can be used to develop bacteria which produces these drugs by inserting a genome into a bacterial cell with removed DNA and letting it divideto relpicate the DNA. can be exisiting DNA sequences or create new ones

Nonotechnology uses tiny synthetic particles to deliver drugs to a very sepcific site within a cell

EG E.Coli and yeasts are genetically modified to produce a precursor (drug that will be activated to become the drug) of an antimalarial drug

EG mamals can also be genetivally modified to produce drugs in their milk EG goats produce human antithrombin which prevents blood clotting

Question 130

how do antibiotics work?

examples

history of antibiotics

whats happening now?

Answer 130

antibiotics interfere with the metabolism of bacteria without affecting the matabolism of human cdells- selective toxicity

they were the 1st time medicines were effective against bacteria so were widely used and commuicable disease deaths dropped

EG. steptomycis, vancomycin, penicillin

are now used for minor infections which the immune system could handle

resistance started with penicillin but some microorgansms are resistant to all

Question 131

how does antibiotic resistance occur?

where is it common?

Answer 131

• antibiotics work as theres a binding site for the drug and a metabolic pathway affected by it
• random mutations can produce bacteria not affected by the antibiotic and this is best fitted to survive and reproduce
• it passes it mutation to daughter cells and reproduces rapidly
• bacteria have 1 copy of a gene- a single loop of double stranded DNA so mutations have an immediate effect
• antibiotics can then kill the weaker ones so that the restant bacteria become more common so you get a resistant strain
• common in care homes and hospitals where antibiotics are often used and people have weak immune system

Question 132

MRSA and clostridium difficile

Answer 132

MRSA

• bacterium carried in 30% of population on sin and nose
• enters through cut or medical procedure
• causes boils, abcesses and potentially fatal scepticaemia and neumonia
• was treated effectively with methicillin, a penicillin like antibiotic but mutated to be resistant strains

C.Difficile

• bacteria in guts of 5%
• produces toxins that damage the lining of intestines cauing dirrhoea, bleeding and death
• no problem for healthy people but when antibiotics kill of helpul bacteria in gut it can survive and reproduce rapidly

Question 133

how to prevent resistant bacteria

Answer 133

• need to minimise use and ensure complete course so resistan individuals are less likely to survive and become a resistant strain
• good hygiene

Question 134

Graph for priamry and secondary response

Answer 134

Question 135

why is there no vaccine for malaria?

Answer 135

it spends time in erythrocytes so it is protected by self antigens and its own antigens reshuffle

Question 136

What are the diffferent methods if classification?

Answer 136

biological/ species/ physiological- by observing homologous structures which show common ancestry

phylogeny- based on ancestry and molecular similarities such as DNA and RNA

Question 137

what is convergent evolution?

What is evidence foe this?

what are analogous structures?

what are homologous strctures?

why does alll of this mean classifying species can be less accurate and how can you be more accurate?

Answer 137

some animals are unrelated but have evolves similar adaptations to their environment

anatomical adaptations

EG birds, bats and insects all have evolved with wings but are very different

serve the same purpose but are structually veyr different

EG bird and insect wings

structures that have developed from the same limb

EG bat and bird wings

• more accurate to DNA type them

Question 138

What methods enabled another assessment of the classification system by Woese in 1990 to 3 domains?

What protein can be used to determine evolutionary links?

Answer 138

now study genetics and biological molecules. when you eveolve, your internal and external features change so therefore DNA does too as it determines the proteins therefore the characteristics. it uses differences in sequence of nucleotides in cells rRNA and lipid membranes structure as each domain is different

haemoglobin has 4 polypeptide chains with a fixed number of amino acids

chimpanzees only have 1 different aa, gorillas have 3, indicating common ancestory

Question 139

What are the 3 domains?

which are prokartotes?

Answer 139

bacteria forming eubacteria

archaea forming archaeabacteria

eukaryotes forming protoctista , plantae, fungi and animalia

eubacteria and arcjaea are both prokaryotes

Question 140

Features of domains

Answer 140

Question 141

What does it mean if 1 branch is smaller at an equivalent time on a tree?

Answer 141

extinct

Question 142

Why can recalssification necessary?

Answer 142

archaea ad eukaryotes had lots in common

1. similar cell membrane structure
2. simialr flagella structure
3. same form of RNA polymerase
4. proteins bound to genetic material
5. similar mechanisms for DNA replication and building RNA

Question 143

what is the purpose for cytochrome C?

Answer 143

is a protein used in respiration in all living organisms (not chemosynthetic organisms)

made from a sequence of aa which varies slightyl from species to species

if thr sequence is very similar between 2 species we can infer they are closely related

we could also comapre DNA or RNA sequqnces

Question 144

What is an adaptation?

What makes a well adapted organism?

Answer 144

a characteristic that increases an organisms chance of survival and reproduction in its environment

1. find enough food or photosynthesise well
2. find enough water
3. defend itself against predators and disease
4. survive physical conditions of environment
5. respond to changes in its environment
6. have enough energy to allow successful reproduction

Question 145

What is the main difference and similarity betwen the marsupial and placental mole?

Answer 145

different taxa as reproduce different and seperated from common ancestor 100 mill years ago

Placental- placenta connects embryo to mothers circulatory system in the uterus so the embryo reaches a high level of maturity before birth. dark grey

Marsupial- start life in the uterus but leave and enter the marsupium pouches when they are still embryos and suvk milk to mature here. light brown/orange

adapted same due to similar conditons

both burrow throughsoft soil to find worms and grubs and have modified fore limbs for digging. velvety fur for smooth movement and simialr shape (long)

Question 146

What types of adaptations are there?

Answer 146

anatomical (physical features internal and external)

physiological (internal processes and functions of the body systems)

behavioural (inherited or learnt)

Question 147

What tyoes of anatomical adaptations are there and examples?

Answer 147

body covering- feathers, hair and shells for flying, warmth and protection

mimicry appearance- think harmful/ poisonous eg hoverfly mimics wasp

camoflauge- white snows have white hair in winter and brown in summer

teeth- tigers and sharp and big to kill prey

Question 148

behavioural

Answer 148

survival behaviour - possoms play dead

courship- elaborate to attract mate and more chance of reproducing eg scorpois dance

seasonal behaviour- migration for climate and food andhibernation where they are inactive and have reduced HR + temp to conserve enegy eg brown bear in winter

innate- genes eg spiders make their webs

learned- from experience or watchign others eg sea otter uses stones to hammer shells off rocks

Question 149

physiological adaptations and examples

Answer 149

poison production- reptiles produce venom to kill prey

antibiotic production- bacteria try to kill other bacteria species

water holding- cacti

Question 150

Blue gum example for adaptations

Answer 150

Structural: vertical leaves to reduce light exposure and transpiration, thick bark to protect from fire

Behavioural: releases seeds after a fire so less competition from other plants

Physiological: Leaves produce toxic compounds to deter grazing

Question 151

Fennec fox example for adaptations

Answer 151

Structural: large ears for hearing and heat loss, eyes for predation, thick fur for the cold nights hunting

Behavioural: Nocturnal to avoid heat and predation from eagles and are in underground burrows in day

Physiological: kidneys reabsorb most water to concentrate urine to avoid dehydration

Question 152

thermophilic archae example for adaptations

Answer 152

Structural: membranes have strong ether linkages . DNA has a high proportion C-G and so compact to withstand heat. Proteins have many polar amino acids to stabilise the tertiary structure

Behavioural: form a matrix that sticks bacteria to a biofilm to help withstand the high temperatures

Physiological: produce heat shock proteins to protect the cell. A heat resistant polymerase so replication still occurs at high temperatures.

Question 153

whay cant differences in DNA data tell us what weather to put species in the same genus?

Answer 153

• There is no clear definition of what a genus is and what criteria should be used for placing different species in the same genus.
• If we use DNA sequences in this way, there is no agreement about whether it is more valid to look at every part of the DNA in a species or whether we should concentrate on particular areas, such as the coding
• We can also question whether sheer numbers of differences in DNA bases can justifiably be used to determine classification, or whether we should take into account their effects as well.

Question 154

are the five-kingdom and the three-domain classifications completely different from one another, or could they possibly be used together

Answer 154

The three domains are the highest taxa.

It is possible to have the domain Eukarya, with the kingdoms Protoctista, Fungi, Plantae and Animalia as subdivisions of it.

However, we cannot keep the kingdom Prokaryota, as that is now split at a higher level.

Question 155

What is variation?

Answer 155

• The presence of variety/ difference between individuals leading to adaptations and evolution (natural selection)
• Can occur within a species (intra specific variation), or between species (inter specific variation)

Question 156

What are the types of variation?

Answer 156

Continuous

• 2 extremes and a full range of intermediates.
• Most individuals are close to the mean value, with the number of individuals at the extremes being low.
• EG. Height or length of leaves.
• Can be due to genetic or environment and usually a combination of many different alleles and genes (polygenic) and then affected by environment too.
• Often assigned numerical values but not always lie eye and skin colour.

Discontinuous

• 2 or more distinct categories with no intermediate values, often categories have a label not a number.
• Members of a species may be evenly or unevenly distributed between categories.
• EG. Human blood groups, colour of flowers, drug resistant and drug susceptible TB.
• Mainly due to genetic variation and little influence of environment, and often determined by a single gene with one 2 or 3 possible alleles. (largely monogenic)

Question 157

What are the 2 main causes of variation?

Answer 157

Genetic

• alleles are different forms of the same gene, all organisms have different combinations of different alleles.
• In sexually reproducing organisms it comes from events in meiosis- crossing over in prophase 1, independent assortment in metaphase, random fusion of gametes, and you inherit alleles from each parent so is different from parents.
• It may also arise from random mutations in DNA. Mutations must occur at the gamete so new cells can be passed onto future generations not just the individual itself. If thy occur in somatic cells (body) then only the individual is affected. Both cause variation.
• Allozymes are enzyme variants that are coded by different alleles of the same gene. Isozymes all catalyse the same reaction but are coded by different genes. They may be able to work at different temps.

Environment

• not all genes are active at once. The environment can affect which genes are active at a time.
• Food- obesity, sun- skin colour.
• It is not inherited.
• Plants are more affected by environmental variation as they can move less.
• Scars are completely environmental.

Can be a combination

• if you have tall parents you will probably inherit genes to grow tall but if you eat a poor diet and suffer from disease you may not be tall

Question 158

What were darwins 4 observations?

Answer 158

1. All organisms reproduce to give far more offspring than are going to survive
2. Populations of organisms fluctuate but don’t tend to increase and decrease significantly over time- their number remain fairly constant
3. There is variation among individuals in many of their characteristics- intraspecific variation caused by sexual reproduction
4. Offspring resemble their parents- features are transmitted from one feature to the next.

Question 159

What were Darwins 4 inferences?

Answer 159

1. In ‘on the origin of species’, there is a struggle for life- there is competition between organisms in the same population for limited resources
2. The organism that are successful in competing for resources have features that mean they are adapted to their environment. They have a higher chance of surviving than individuals that are not so well adapted. Those that are successful in competition live long enough to reproduce
3. The organisms that reproduce pass on inherited characteristics to the next generation which then contains a higher proportion of offspring from the better adapted parents than from those that are less well adapted
4. The unequal ability to survive and reproduce leads to a gradual change in a population with certain adaptations increasing in frequency over the generations

Question 160

What did darwin and Alfred Wallace do?

Answer 160

Darwin noticed that the shape of finches beaks were adapted to food available on different Galapagos islands. When he returned to England he spent many years developing ideas and carried out experimental breeding of pigeons to gain evidence that his ideas may work.

Wallace spent many years travelling and collecting specimens in south America (Borneo) and in south east Asia. He came up with natural selection. They both had similar ideas of evolution so they proposed the theory of evolution though a joint presentation of 2 scientific papers in the Linnean society of London in 1858.

A year later Darwin wrote his book naming the theory as the theory of evolution by natural selection

Question 161

Evidence of evolution from fossils

Answer 161

• Palaeontology is the study of fossils
• Mineralised animals that have lived and died found in sedimentry rocks
• Only the hard parts mineralise and generally the soft tissues decompose
• Only a small proportion of organisms will be fossilised
• Need specific conditions for fossils to form and are not often present
• We only find a small proportion of fossils so we have a limited view and some are destroyed in volcanoes etc.
• Older fossils show organisms to be smaller and simpler
• We can track fossils over a period of time and observe a sequence of developmental changes and adaptations (evolution)
• Fossils of the simplest organisms like bacteria and simple algae are found in the rocks whilst more complex organisms like vertebrates are in more recent rocks
• The sequence organisms are found matches their ecological link- plants appear before animal fossils as animals need plants to survive
• Can see similarities in anatomy to see how closely related organisms evolved from the same ancestor
• Allow relationships between extinct and living organisms to be investigated

Question 162

Comparative anatomy and morphology for evidence of evolution

Answer 162

Bones in the front limbs of tetrapod’s- amphibians, reptiles, birds and mammals have basically the same pattern even though there are differences between them, indicating they had a common origin

Homologous structures- appear superficially different but has same underlying structure – vertebrates weather swimming, walking, flying has similar limbs so may have evolved from a common ancestor and common structure. This is evidence for divergent evolution when closely related species diversify to adapt to new habitats as a result of migration or loss of habitat.

Question 163

Biochemistry/ DNA as evidence for evolution

Answer 163

• Atoms in aa can be arranged to give 2 molecules that are mirror images of each other- left handed and right handed molecules. Only left handed aa exist in nature.
• There are many possible different types of aa but only 20 are used to make proteins and they are the same 20 in all organisms
• The molecules of inheritance in all cellular organisms, prokaryotes and eukaryotes is DNA so slight changes in this can help identify evolutionary links
• The genetic code that specifies an organisms aa is basically the same in all organisms
• ATP is the universal currency for energy in the cells of all organisms
• Analysis of the aa sequences of proteins reveals proteins from closely related organisms are very similar
• Sequencing DNA nucleotides shoes the relationship between different species- nucleotide sequences in the genes of closely related species are found to be very similar. Similarities and differences can group species and deciding the extent of the differences gives us an idea when speciation occurred.
• Also similar key protein structures like DNA polymerase which repairs and copies DNA has only a few differences between its aa sequence for different phyla and even kingdoms. Any significant changes in this enzyme reflect significant events in evolutionary history.
• Ribosomal RNA and cytochrome c, a protein involved in respiration are commonly studied as they are mainly conserved among species. rRNA has a slow rate of substitution so is used with fossil evidence to determine relationships with ancient species
• Neutral evolution- most variability in the structure of a molecule doesn’t affect its function as most variability occurs outside the molecules functional regions which aren’t affected by natural selection

Question 164

Natural selection

Answer 164

• Genetic variation, selection pressure and reproductive success or failure results in an increased proportion of the population possessing the advantageous characteristic
• Organisms that are best adapted to the environment are more likely to survive and reproduce. As a result of natural selection these adaptations will become more common in the population. Organisms poorly adapted are less likely to survive ad reproduce so characteristics are not passed onto next generation so less of the population displays these characteristics.

1. Organisms within a species show variation in their characteristics that are caused by differences in their genes (genetic variation) different alleles for example from mutations
2. Organisms whose characteristics are best suited to a selection pressure such as predation, competition or disease have an increased chance of surviving and successfully reproducing. Less well adapted organisms die or fail to reproduce – survival of the fittest
3. Successful organisms pass the allele encoding the advantageous characteristic onto their offspring and those without it are less likely to pass it on
4. This process is repeated for every generation and over time the proportion of individuals with the advantageous adaptation increases. Therefore the frequency often allele that codes for this particular characteristic increases in the populations gene pool
5. Over very long periods of time many generations and often involving multiple gens, this process can lead to the evolution of a new species

Question 165

Example of natural selection

Answer 165

EG. Peppered moths- dramatic changes to their environment I the 19th century caused changes in the allele frequency. Before the industrial revolution they were pale coloured to camouflage them against light coloured tree bark and increase their chance of survival. Tress got darker in the industrial revolution as covered in soot so loss of lichen cover caused by increased atmospheric pollutants. Darker ones survived and reproduced so increased frequency f ark moths and the dark allele in the population. Now lighter moths again due to clean air act.

Question 166

Selection pressure

Answer 166

factors that affect the organisms chances of survival or reproductive success (ability to produce fertile offspring)

Question 167

Pre-adaptation

Answer 167

when an organisms existing trait is advantageous for a new situation.

Question 168

How has evoltion impacted humans?

Answer 168

• Drug resistance
• Pesticide resistance
• Flavobacterium

Question 169

Evolutions impact on humans: drug resistance

Answer 169

• Antibiotics soon became less effective as bacteria developed resistance, due to a few bacteria which naturally possessed genes that helped them prevent the effect of the antibiotic
• EG penicillin is effective as it prevents the growth of cell walls in some bacteria. Resistant bacteria have enzymes that can break down penicillin, and when antibiotics are used, they have an advantage as they are adapted to new conditions. There is then less competition for the resistant bacteria as they have been killed so the resistant ones survive and reproduce to pass on their genes to offspring. EG MRSA (methicillin resiatant S. aereus)

Bacteria gain resistance by:

1. A gene on the chromosome spontaneously mutating to give a form that codes for a polypeptide that is not affected y the antibiotic
2. A bacterium may gain a plasmid with a gene for resistance from another bacterium, even from an individual of a different species

As bacteria only have 1 copy of each gene since they only have a single loop of double stranded DNA. They are essentially haploid so a mutant gene for antibiotic resistance will have an immediate effect on any bacterium with it. They also reproduce very quickly asexually by binary fission.

Usually, the few bacteria that aren’t eliminated will be eliminated by the immune system so eventually the entire population will be killed but if the dose is not correctly followed then the less susceptible bacteria can survive. TMT next time there’s an infection with thin bacteria strain the antibiotic won’t be as effective. Some strains are untreatable.

Ways to reduce resistance:

• Only prescribe antibiotics when absolutely necessary and don’t prescribe them for no bacterial diseases just in case
• Ensure people finish their course of antibiotics
• Rotate antibiotics so that one type is not used continuously in the treatment of a specific disease
• Keep some antibiotics as a last resort
• Invest in research to find new antibiotics

Question 170

Evolutions impact on humans: pesticide resiatance

Answer 170

• Used to kill pests of crops and vectors of diseases – EG Colorado potato beetles and anopheles tranmit malaria
• Monoculture provides lots of food for insects so if other conditions are good then they will increase in number rapidly
• Resistant insects will survive and reproduce as there is less competition
• The insecticide is the selective agent
• This reduces food security for the future as evolution of resistant strains means we need to find new chemical controls, use them sparingly or rotate them so they’re not used all the time which helps extend the useful life of pesticides. 2 or more pesticides can be mixed which delays the time for resistance to emerge and spread. Also only use them when they know their crops are at risk, not to prevent an invasion of pests
• Biological control is an option where natural parasites and predators of the pest species are released
• Selective breeding can develop new crop varieties that are resistant to pests
• Genetically modifying crops to make toxins that kill pests

Question 171

Flavobacterium

Answer 171

Most evolution occurs as a negative result of selection pressure, but some occurs due to opportunities that have arisen in their environment. A new strain of flavobacterium is living in waste water from factories that produce nylon 6, that makes toothbrushes and violin strings. Humans use it to digest and clear u factory waste as they contain enzymes called nylonases which provides them with a source of nutrients. These enzymes were probably caused by a mutation.