communicable diseases

Question 1

Name some means of transmission

Answer 1

-Direct physical contact, such as touching, a person who is infected or touching contaminated surfaces
-faecal-oral transmission- by eating food or drinking water contaminated by the pathogen
- Droplet infection in which the pathogen is carried in tiny water droplets in the air
-Transmission by spores, these can be carried in the air or aside on surfaces or in the soil

Question 2

Name some factors affecting transmission

Answer 2

human migration
Ease of travel
Poverty
Cultural practices
Climate change

Question 3

What is an endemic?

Answer 3

a disease that is always present in a population

Question 4

What is a pandemic?

Answer 4

An epidemic occurring across international boundaries

Question 5

What is an epidemic?

Answer 5

there is a large increase in the number of cases in a population

Question 6

examples of cultural practices

Answer 6

e.g. in Africa, it is common practice to touch and kissed a dead during the burial service. This increase the spread of Ebola in 2014.
e.g. Common to cremate corpses on the banks of the Ganges, and in some cases to flip the cups down the river. The Ganges provides drinking water for over 400, million people.

Question 7

human migration

Answer 7

colonising forces bring pathogens with them and infect the native people who would have never been exposed to these pathogens, and so have no immunity or resistance
e.g. The Europeans arriving in the north and South America bringing smallpox with them.

Question 8

physical defences of plant

Answer 8

-waxy cuticle- waterproof to reduce water loss and prevent pathogens from coming into direct contact with the epidermal cells, which reduces the risk of infection
-Cell wall
-callose deposition (a polysaccharide that gets deposited between the plant cell walls and plasma membrane during times of stress, E.G. pathogen invasion, and this makes it harder for pathogens to enter the cell)
-stomatal closure

Question 9

What is a physical defence?

Answer 9

barriers that prevent microorganisms from entering the plant

Question 10

What is a chemical defence?

Answer 10

substances secreted by the plant to kill microorganisms

Question 11

chemical defences of a plant

Answer 11

-insecticides- chemicals naturally produced by plants, to kill insects as well as insect eggs and larvae
-Insect repellent- repel the insect vectors that carry disease, such as a female mosquitoes, which transmit the pladomium parasite that causes malaria
-cyanide
-Antifungal compounds
-Antibacterial compounds - kill bacteria by destroying bacterial cell walls and interfere with the ability to reproduce or make proteins and nutrients needed to survive

Question 12

What is necrosis?

Answer 12

deliberate cell suicide
A few cells are sacrificed to save the rest of the plant
By killing the cells surrounding the infection, the plant can limit the pathogen’s access to water and nutrients to stop it from spreading further around the plant

Question 13

Name some human defences against pathogens

Answer 13

-skin- a physical barrier
mucous membranes - secrete mucus that traps pathogens and contains antimicrobial enzymes
-Blood clotting- plug wounds to prevent pathogens from entering and blood loss
-Inflammation- release of histamine causes vasodilation, which makes the capillary walls more permeable and increases blood flow for white blood cells
-Wound repair using collagen fibres- the surface is repaired by the outer layer of skin, dividing and migrating to the edges of the wound tissue below and contracts, bringing edges of the wound close together
-Expulsive reflexes- e.g. coughing and sneezing that happens automatically