Pathogens

Question 1

What is a communicable disease and how is it caused?

Answer 1

Diseases that can be passed on from one organism to another

Caused by infectious organisms known as pathogens

Question 2

How are communicable diseases spread in plants?

Answer 2

Directly from plant to plant or vectors (carry pathogens from one organism to another)

Question 3

Bacteria

Answer 3

Some bacteria are pathogenic and cause communicable diseases
Are prokaryotes- no membrane bound organelles or nucleus
Can be classified by their cell wall- gram staining can identify this. Gram positive appear purple/blue when stained whereas gram negative appear red

Question 4

Viruses

Answer 4

Non living infectious agents (cant replicate genetic material/ synthesise proteins)
Basic structure- genetic material surrounded by a protein
They take over the host cell metabolism, Viral genetic material gets inserted into the host DNA, and the viruses use the host cell to reproduce and synthesise more viruses. The viruses eventually burst out of the cell, destroying it and spread to infect other cells.

Question 5

Protists

Answer 5

Unicellular eukaryotes

Parasitic- use animals or people as their host organism

Question 6

Fungi

Answer 6

Eukaryotic organisms
Parasitic fungi cause diseases (feed on living plants and animals- digest and destroy them)
Affect the leaves of plants and stop them from photosynthesising- kill the plant
Have hyphae which form a network and spread throughout a host/ soil- allow fungi to spread rapidly

Question 7

How do bacteria damage host tissue?

Answer 7

Produce toxins that damage the cell in some way, eg:

Break down cell membrane, inactivate enzymes, interfere with genetic material so the cells cannot divide

Question 8

Ring Rot

Answer 8

Bacterial disease of potatoes and tomatoes
Caused by gram positive bacteria
Damages leaves, tubers and fruit

Question 9

Tobacco mosaic virus

Answer 9

Virus infecting plants eg tomatoes,peppers,cucumbers
Damages leaves, flowers and fruit
Causes leaf curling and yellow leaves
Can be caused by direct contact of plants or spread by the aphid vector

Question 10

Potato blight

Answer 10

Caused by protoctist
Transmitted via spores- hyphae penetrate host cells, destroy leaves, tubers and fruit
Causes browning of the leaves

Question 11

Black sigatoka

Answer 11

Banana disease caused by a fungus which destroys the leaves as it stops photosynthesis
Hyphae penetrate/ digest the cells- leaves go black
Land cannot be used to grow crops again for X number of years, crop rotation, use fungicides, prevent overcrowding

Question 12

Tuberculosis

Answer 12

Bacterial disease- myobacterium tb
Damages and destroys lung tissue and supresses the immune system so it is more susceptible to other diseases
Curable by antibiotics and preventable by improving living conditions

Question 13

Meningitis

Answer 13

Bacterial infection of the brain which can spread into the rest of the body causing blood poisoning and death
Blotchy red rash that does not disappear when a glass is pressed against it
Antibiotics and vaccines

Question 14

HIV/ AIDS

Answer 14

Targets T helper cells in the immune system- destroys the immune system so the body is less able to fight off other diseases
Passed via bodily fluids- unprotected sexual intercourse, sharing of needles, mother to child
No vaccine or cure

Question 15

Influenza

Answer 15

Viral infection- kills ciliated epithelial cells leaving the airways open to secondary infection
High temperature, body ache, fatigue
Flu vaccine is given annually to protect against changing strains (mutations cause a change in the antigens)

Question 16

Malaria

Answer 16

Caused by protoctista
Spread by the vector anopheles mosquitoes which passes the parasite into the blood stream
Invades red blood cells and liver
Use insecticides, remove standing water where the anopheles breeds, use mosquito nets, long sleeved clothing

Question 17

Ring worm

Answer 17

Fungal disease
Grey white crusty circular areas of skin, may be itchy
Antifungal cream
Thrives in heat and moisture

Question 18

Athletes foot

Answer 18

Fungal disease
Grows on/ digests the warm moist skin between the toes
Causes cracking and scaling - itchy and sore
Antifungal creams
Spread directly or from towels/ clothing

Question 19

How are communicable diseases transmitted?

Answer 19

Direct transmission- directly from one individual to another (skin to skin contact, inoculation- break in the skin, ingestion)
Indirect transmission- pathogen travels from one individual to another indirectly (inanimate objects like bedding or socks, inhalation of droplets as you cough or sneeze, vectors, water)

Question 20

Which factors affect the transmission of communicable diseases in animals?

Answer 20

Overcrowded living conditions
Poor nutrition
Compromised immune system 
Culture- eg female genital mutilation
Poor disposal of waste- providing a breeding site for pathogens

Question 21

How are communicable diseases transmitted between plants?

Answer 21

Direct contact of a healthy plant with any part of a diseased plant
Indirect- soil contamination as spores, vectors (wind, water, animals, humans)

Question 22

Which factors affect the transmission of communicable diseases in plants?

Answer 22

Planting crops that are susceptible to disease
Over crowding- increases likelihood of plant contact
Damp, warm conditions increase survival and spread of pathogens
Poor mineral nutrition- reduces resistance