Chapter 12// Communicable Diseases

Question 1

communicable disease

Answer 1

diseases that are caused by pathogens and can be passed from one organism to another, of the same or different species

Question 2

pathogen

Answer 2

either bacteria, fungi, virus or protoctista microorganisms that cause disease

Question 3

vector

Answer 3

a living or non-living factor that transmits a pathogen from one organism to another e.g. malaria mosquito

Question 4

non- communicable diseases

Answer 4

diseases that can not be passed from one organism to another e.g. diabetes/ cancer

Question 5

Do bacteria have membrane bound organelles?

Answer 5

No

Question 6

How can bacteria be classified?

Answer 6

By their cell walls— different cell walls react differently with gram staining

GRAM POSITIVE BACTERIA= look purple/ blue under microscope

GRAM NEGATIVE BACTERIA= look red

This is useful as we know by the type of cell wall how bacteria react to different antibiotics

Question 7

bacteriophage

Answer 7

viruses that attack bacteria use bacterial cells as hosts destroying bacteria after they replicate

Question 8

what vector transfers malaria and what kingdom does it belong to

Answer 8

plasmodium

Kingdom: protoctista

Question 9

are protoctista single-celled eukaryotes

Answer 9

yes

Question 10

are fungi single-celled?

Answer 10

yes

Question 11

saprotrophic feeding

Answer 11

release enzymes to decompose dead organic matter

Question 12

Parasitic

Answer 12

feed on living plants/ animals

Question 13

pathogen modes of action: fungi

Answer 13

fungi digests living cells and destroys them

Some fungi produce toxins

Question 14

pathogen modes of action: bacteria

Answer 14

bacteria produce toxins causing diseases e.g. some bacterial toxins break down cell membranes or inactivate enzymes

Question 15

pathogen modes of action: protoctista

Answer 15

Protoctista take over cells by digesting them and using the cell contents to reproduce e.g. malaria

Question 16

pathogen modes of action: virus

Answer 16

viruses take over cell metabolism// viral genetic material is inserted into host cell, the host cell uses viral DNA to make more viruses, cell bursts and dies releasing more virus = spreads 🦠

Question 17

What is ring rot caused by, what plants does it affect

Answer 17

Caused by GRAM POSITIVE BACTERIA

affects potatoes, tomatoes + aubergines

Question 18

What is tobacco mosaic virus caused by, what plants does it affect

Answer 18

caused by TMV VIRUS

Affects tobacco plants, tomatoes, peppers, cucumber + petunias 🥔🍅🥒🚬🌷

Question 19

What is potato blight caused by, what plants does it affect

Answer 19

Caused by FUNGUS LIKE PROTOCTISTA

Affects tomatoes + potatoes 🥔 🍅

Question 20

What is black sigatoka caused by, what plants does it affect

Answer 20

Caused by FUNGUS which attacks + destroys leaves, hyphae penetrate + digest cells turning leaves black

Affects bananas 🍌

Question 21

Tuberculosis

Answer 21

• bacterial disease (Mycobacterium tuberculosis and M.bovis)
• effects humans, cows, pigs, badgers + deer
• TB damages lung tissue and suppresses immune system making body less able to fight disease
• TB is both curable by ANTIBIOTICS and preventable thru vaccination and better living conditions

Question 22

Bacterial Meningitis

Answer 22

• bacterial infection (streptococcus pneumoniae)
• effects children between 15-19
• infection of meninges of the brain which spreads to rest of the body causing septicaemia (blood poisoning and rapid death)
• antibiotics will cure the disease if delivered early + vaccines protect against some forms

Question 23

HIV (human immunodeficiency virus) causes AIDS (acquired immunodeficiency syndrome)

Answer 23

• virus (HIV) targets T Helper cells in the immune system, gradually destroying the immune system so ppl affected are open to other infections such as TB/ pneumonia
• effects humans and non-human primates
• HIV is a retrovirus with RNA in its genetic material contains enzyme REVERSE TRANSCRIPTASE which transcribes the RNA to a single strand of DNA which interacts with genetic material of host cell
• there’s no cure but ANTIRETROVIRAL drugs slow the progress of the disease— u must take a combination of antibiotics cuz otherwise get resistant

Question 24

Retrovirus

Answer 24

Any group of RNA virus which insert a DNA copy of their genome to replicate in host

Question 25

Give 4 ways HIV can be spread

Answer 25

unprotected sex, through bodily fluids Shared needles Contaminated blood Mother to baby through birth/ breastfeeding

Question 26

Influenza (flu)

Answer 26

- viral infection : orthomyxoviridae of the ciliated epithelial cells in the gas exchange system, killin them leaving airways open for infection - flu viruses mutate regularly, sometimes major antigen changes cause a flu epidemic

Question 27

Malaria

Answer 27

- caused by parasitic plasmodium protoctist spread through ANOPHELES mosquito The plasmodium parasites reproduce inside female mosquitoes, the fem.mosquito needs protein from blood to lay eggs so feeds on people which is how ppl are infected (invades red blood cells, liver + brain) There is no vaccine but preventative measures are effective — destroying by insecticide + remove standing water, window screens and clothing to prevent bites

Question 28

Ring worm

Answer 28

- fungal disease - affecting humans, cattle,dogs and cats - antifungal creams are an effective cure

Question 29

Athlete’s foot

Answer 29

- fungal disease (form of ringworm) caused by TINIA PEDIA - grows on + digests warm moist skin between toes causing scaling - antifungal creams effective cure

Question 30

Direct transmission definition

Answer 30

pathogen transferred directly from one person to another

Question 31

Indirect transmission definition

Answer 31

Pathogen travels from one individual to another indirectly

Question 32

Describe 4 ways pathogens are DIRECTLY transmitted in animals

Answer 32

• DIRECT CONTACT =kissing/sex, direct skin to skin contact, microorganisms from faeces on hands • INOCULATION = break in skin (HIV during sex), from animal bites, sharing needles • INGESTION = taking in contaminated food/drink • TRANSMISSION FROM INFECTED ANIMAL = cat scratch disease/ rabies

Question 33

Describe 3 ways pathogens are INDIRECTLY transmitted in animals

Answer 33

^FOMITES = objects like bedding, socks or cosmetics transfer pathogens when shared ^ DROPLET INFECTION (inhalation) = drops of saliva/mucus expelled from ur mouth contain pathogens breathed in by others ^ VECTORS =transmit communicable pathogens from one host to another (mosquitoes transfer malaria, water can also act as a vector of disease like diarrhoea)

Question 34

factors affecting transmission of communicable diseases in animals

Answer 34

* poor nutrition * compromised immune system e.g. patient w HIV * poor disposal of waste— become breeding sites for vectors * climate change

Question 35

factors affecting transmission of communicable diseases in plants

Answer 35

🦠 overcrowding increases likelihood of contact 🦠 poor mineral nutrition reduces resistance of plants 🦠planting crops susceptible to disease 🦠damp warm conditions, increase spread of pathogens or spores

Question 36

Ways in which pathogens are DIRECTLY transmitted between plants

Answer 36

direct contract of a healthy plant w any part of a diseased plant

Question 37

Ways in which pathogens are INDIRECTLY transmitted between plants

Answer 37

* soil contamination = infected plants leave pathogens or reproductive spores from fungi in the soil (e.g. black sigotoka spores left in soil contaminate the next crop) * vectors such as: WIND (bacteria or viruses or spores carried by wind to other crops), WATER (spores in water + raindrops carry pathogens), ANIMALS (carry pathogens from one plant to another, HUMANS (pathogens/ spores transmitted by hands)

Question 38

plant defended against pathogens

Answer 38

PHYSICAL DEFENCES = when plant attacked by pathogens it sets up mechanical defenders: produces CALLOSE polysaccharide between cell walls to strengthen them (blocks siege plates in phloem sealing off spread of pathogens) and LIGNIN is added to make barrier to invasion CHEMICAL DEFENCES = produce insect repellent e.g. citronella, produce insecticides e.g. pyrethins+ caffeine, produce antibiotics e.g. phenols, gossypol, produce anti-oomycetes e.g enzymes that break down GLUCANS found in oomycete cell walls, produce general toxins e.g. cyanide when attacked