Module 4: Biodiversity, Evolution And Disease

Question 1

What are pathogens and what are the types of pathogen?

Answer 1

Pathogens are microorganisms that can cause disease. Pathogens are either bacteria, viruses, fungi or protists

Question 2

Give 3 examples of bacterial diseases

Answer 2

TB causes disease in animals. It damages lung tissue and suppresses the immune system which makes the victim more susceptible to other diseases. Bacterial meningitis also affects animals. It damages the meninges in the brain which can cause septicaemia in other parts of the body. Ring rot affects plants, mainly tomatoes, potatoes and aubergines. It attacks the leaves, tubers and fruit.

Question 3

Give 3 examples of viral diseases

Answer 3

AIDS affects humans and other primates. It destroys the immune system, making the victim more susceptible to other diseases. Influenza affects mammals. It kills the ciliates epithelial cells in the gas exchange system which opens the airways to other diseases. Tobacco mosaic virus affects plants. It damages the plants leaves which prevents photosynthesis and therefore growth and it also damages the fruits which affects crop yield

Question 4

Give 3 examples of fungal diseases

Answer 4

Ring worm affects cows. It causes infectious, crusty areas of skin to form. Athlete’s foot is a type of ring worm that affects humans. It feeds of the skin in between the toes which makes them crusty, dry and sore. Black Sigatoka affects banana plants. It damages the leaves of the tree which affects photosynthesis and therefore both growth and crop yield

Question 5

Give 2 examples of protist diseases

Answer 5

Malaria affects animals. It attacks the liver, red blood cells and sometimes the brain. Blight affects potato and tomato plants. It attacks the leaves, tubers and fruits

Question 6

How can animal-affecting pathogens be transmitted directly and how can it be prevented?

Answer 6

Direct contact is where skin to skin or mouth to mouth contact leads to the spread of pathogens from one individual to another. It can be prevented through hygiene and isolating when you have a disease
Ingestion is eating/drinking contaminated food and drink. Fecal-oral transmission comes under this category as drinking contaminated water causes cholera. This can be prevented by making sure food is cooked properly and healthily and that countries have good sanitation
Inoculation leads to the spread of diseases such as HIV during sex and rabies from animal bites. Using shared needles also spreads disease. It can be prevented through throwing away used needles and treating open wounds

Question 7

How can animal-affecting pathogens be transmitted indirectly?

Answer 7

Fomites are inanimate objects that pathogens can rest on before being touched by another healthy person which causes them to spread. This can be prevented by wiping down surfaces
Droplets when people talk, sneeze and cough can spread pathogens around. This can be prevented by masks, distancing and good ventilation in rooms
Vectors such as animals, wind(which is just droplet infection) and water can spread disease long distance from human to human. Animal vectors can be prevented by insect repellent and other traps/poisons

Question 8

What are some general factors that lead to the spread of animal-affecting pathogens?

Answer 8

Overcrowded living and working conditions increases the chance of direct contact and droplet infection
Poor nutrition and compromised immune systems make people more susceptible to other diseases
Climate change means that pathogens can live for longer and in a wider amount of places which makes them harder to contain
A lack of trained health workers in undeveloped countries increases spread of transmission

Question 9

How do plant-affecting pathogens spread and how can this be prevented?

Answer 9

Direct contact can happen either when plants are grown closely together or when infected plant matter is carried across the wind and comes into contact with other plants. This can be prevented by growing plants in isolated places such as greenhouses. Contaminated soil can cause plants to get diseases through the roots, it can be prevented by growing plants in pots or treating the soil with chemicals. Wind and water can carry spores and other pathogens from plant to plant. This can be prevented by growing plants in greenhouses. Animal vectors can also spread plant pathogens. This can be prevented by either killing the vector directly or bringing in predators to control the population.

Question 10

What are some general factors that spread plant-affecting pathogens?

Answer 10

Planting many plants and/or different types of plants closely together increases infection rate. A lack of minerals decreases plants resistance to disease which makes them more susceptible to disease. Dark, damp, warm living conditions due to climate change or just where they’ve been grown leads to better conditions for pathogens which allows them to spread

Question 11

How does skin prevent pathogens from entering the body?

Answer 11

Skin cells at the surface would have produced a lot of keratin, which makes them dead and impermeable. This prevents pathogens from entering the skin

Question 12

How do mucous membranes prevent pathogens from entering the body in certain areas?

Answer 12

In areas of the body where exchange takes place, there are less barriers which maximises exchange rate but increases vulnerability to pathogens. Goblet cells underneath the surface of tissue membranes produce mucus to trap pathogens so they don’t enter the body

Question 13

How does blood coagulation work and how does it prevent pathogens from entering the body?

Answer 13

And a person cuts themself, the wound is exposed. Platelets in the blood release thromboplastin which sets of a series of chemical reactions which results in the blood clotting and forming a scab, which prevents pathogens from entering the body. Serotonin is also released to narrow the walls of the smooth muscle to reduce blood supply

Question 14

What is the process of phagocytosis?

Answer 14

1.Chemicals produced by pathogens attract the phagocyte to the pathogen
2. Phagocytes recognise non-self antigens(with the help of opsonins) and engulf the pathogen
3. The pathogen is packaged in a phagosome which binds to a lysosome to form a phagolysosome
4. Lysins digest the pathogen.
For macrophages only:
5. The antigens are cut off of the pathogen and are combined with glycoproteins in the cytoplasm to form the major histocompatibility complex
6. The MHC moves the antigens and presents them at the membrane of the phagocyte which turns it into an antigen presenting cell
For both neutrophils and macrophages
7. Dead, soluble pathogen matter is transported out of the cell by exocytosis, useful parts are absorbed into the cytoplasm

Question 15

What are the 3 domains and which kingdoms reside in each one?

Answer 15

Bacteria contains eubacteria, archae contains archaebacteria and eukarya contains protoctista, fungi, plantae and animalia

Question 16

What are the main differences between the 3 domains?

Answer 16

The main difference between all 3 is their ribosomal rNA. Bacteria and archaea can be differentiated by the fact that bacteria have peptidoglycan in their cell walls whereas archaea don’t.

Question 17

What is the general process of the specific immune response?

Answer 17

1. Antigen is encountered
2. Clonal selection- the T or B cell that has the complementary receptors(T)/antibodies(B) detects the pathogen’s antigens
3. Clonal expansion- the T or B cell divided by mitosis to make memory cells as well as specified cells to fight off the pathogen
4. Action- the specified lymphocytes(T killer, T helper, T regulators and B plasma cells) perform their different tasks to kill the pathogen

Question 18

What are the different types of T and B cells and what are their purposes?

Answer 18

T helper cells- these bind to antigen presenting cells. They release interleukins to stimulate the activity of B cells, the production of other T cells as well as stimulating macrophages to undergo phagocytosis
T killer cells- these kill infected cells. They produce perforin which makes holes in the membrane of infected cells which kills them
T regulatory cells- these supress the immune system to regulate and control it. They stop the immune system once a pathogen has been killed and make sure the body recognises self cells to prevent autoimmune diseases
T memory cells- these live a long time and allow the body to produce lots of T cells when a pathogen is detected again(immunological memory)
B plasma cells- each one has an antibody thats complementary to a specific antigen. They release them to the antigens when they recognise them
B effector cells- these reproduce to produce plasma cells
B memory cells- these play a role in immunological memory. Each one has antibodies for a specific antigen and help the body give a rapid response

Question 19

What is cell mediated immunity?

Answer 19

When macrophages engulf pathogens, they become an antigen-presenting cell. Some T helper cells have receptors that are complementary to the antigens and will bind to them. They will then release interleukins which stimulates the T helper cells to clone themselves and produce T memory cells to give immunological memory

Question 20

What is humoural immunity?

Answer 20

When a B cell’s antibodies come into contact with the pathogen whose antigens the antibody is complementary to, the antibodies bind to the antigens and the pathogen becomes and antigen-presenting cell. T cells can bind to that and then release interleukins which stimulates B cells to divide into plasma and B memory cells. Plasma cells produce antibodies for the primary immune response. B memory cells give immunological memory for the secondary immune response.

Question 21

What are autoimmune diseases and how can they be stopped?

Answer 21

When the immune system fails to recognise self cells, the immune system will attack the body, causing diseases such as type 1 diabetes. Immunosuppressants can be taken to suppress the immune system but this means that the body can’t fight off actual diseases as well

Question 22

What is the structure of an antibody and how do they fight diseases?

Answer 22

Antibodies are quaternary globular proteins made out of 2 heavy chains and 2 light chains. They have a varied region which is different for each antibody. This is the binding site where antibodies attack to antigens to make antigen-antibody complexes, which prevents pathogens from being able to invade cells. Antibodies have a hinge region which gives them 2 varied regions. This means that one antibody can bind to two different pathogens to create a chain/bundle of pathogens together(agglutination). The constant region of an antibody acts as a receptor so antibodies can act as opsonins.

Question 23

What are the 2 types of natural immunity?

Answer 23

Natural passive immunity is when a mother transfers antibodies to her foetus/newborn baby through the placenta(foetus) or breast milk called colostrum(newborn baby) to give the baby time for their immune system to develop. Natural active immunity is when your T and B cells clone into T and B memory cells that live a long time so when a pathogen is encountered a second time, the body can fight it off quicker

Question 24

What are the two types of artificial immunity?

Answer 24

Artificial passive immunity is when antibodies from an animal are directly injected into a human to help them fight off a disease such as rabies. Artifical active immunity(vaccinations) is when a substance containing the antigens of a pathogen is injected into humans to all their T and B cells to detect it and replicate so when the human encounters the actual disease for the first time they already have their secondary immune response

Question 25

What is phylogenic classification and what are its advantages over the Linnean heirarchal classification?

Answer 25

Phylogeny is the study of evolutionary relationships between organisms. Organisms are classified on phylogenic trees which show the age and common ancestors of organisms which in turn shows how closely related different organisms are. It uses both observational studies as well as DNA and fossil studies so it’s more accurate than Linnean classification. It also isn’t misleading as the heirarchal classification implies two families or two orders are equal in age and diversity.

Question 26

What are the stages to the production of new medicines?

Answer 26

Discovery: The drug has to be discovered and analysed to see what disease it will work against. It is then tested on lab cells and animals to see if it can be safe to use on humans
Phase 1 trials: it is tested on a small amount of healthy individuals to test for side effects
Phase 2 trials: it is tested on a larger amount of sick people and may include placebo trials as well as comparison to other currently used medicines
Phase 3 trials: it is tested on an even larger amount of people across multiple locations
Liscencing: the drug has to be liscenced by a regular authority before it can be sold

Question 27

What are the main ways we get evidence of evolution?

Answer 27

Fossils: by analysing the structure and age of fossils we can see how species have evolved over time. We can also see how closely related species are and which exctinct species have evolved into which living species. An example is how the leg length and general size of horses have increased over time
Analysing living creatures: creatures such as the galapagos finches and the rock pocket mouse have evolved over time and we can see that by analysing the mice that live on light rock compared to the mice that live on darker rock. This is proof that natural selection happened, causing black furred mice to live on black rocks and light furred mice to live on light rocks
Comparative biochemistry: by analysing DNA and molecules such as ribosomal RNA and cytochrome C, we can compare species and therefore see how closely related they are

Question 28

What are the types of variation?

Answer 28

Interspecific variation is variation between different species. Intraspecific variation is variation between organisms of the same species. All variation is also either genetic, environmental or a combination of both

Question 29

How does evolution mean antibiotics pose a great risk?

Answer 29

When bacterial colonies divide, some of them will be mutated to have antibiotic resistance. If a person then uses antibiotics to kill the bacteria in their body(including the helpful bacteria thah aren’t pathogenic), the resistant ones will have no competition and flourish, leading to antibiotic resistant bacteria growing in larger numbers. Antibiotic resistant bacteria can also conjugate their plasmid to other bacteria, allowing them to have the antibiotic resistant genes too

Question 30

What are adaptations and what are the types?

Answer 30

Adaptations are characteristics that give an advantage to survival or reproduction.
There are 3 main types
Anatomical: physical features both internally and external such as camouflage, shells, spines and specific shaped teeth
Behavioural: actions such as mating dances, pretending to be dead and migration
Physiological: internal process such as the production of venom, the storage of water and reflexes

Question 31

What are homologous/divergent adaptations?

Answer 31

Features of two species that have different functions despite having the same genetic origin. An example is the pentadactyl limbs in both bats and humans. One species uses them for flying(bats’ wings) and the other uses them for running and jumping(human arms)

Question 32

What are analogous/divergent adaptations?

Answer 32

Features of two different species that perform the same function despite having different genetic origin. Examples include wings in both insects and bats, fins in both dolphins and sharks and the smooth, velvety fur in both marsupial moles and placental moles(which are different colours due to their different genetic origins)