Disease

Define non-pathogenic

they do not cause any disease or damage

Outline what Ring Rot does to plants and what pathogen causes it

• Caused by Bacteria

• The bacteria infect the vascular tissue and prevent the transport of water, causing the plant to wilt and die

• The infection spreads into the potato tubers where the vascular tissue is arranged in a ring, producing the characteristic black ring of rot

Outline TB and what pathogen it’s caused by

• Caused by Bacteria

• The bacteria infect the lungs, causing a chronic cough and bloody mucus

• It is a disease often associated with poor hygiene and sanitation

• M. bovine in cows can also transmit to humans to cause TB

Do viruses have a cellular structure?

NO

• This means they can't respire, produce ATP, replicate genetic material or synthesise protein

Outline tobacco mosaic virus and what pathogen causes it

• Caused by a virus

• It causes a distinct yellowing of the leaves which produces a mosaic pattern

What type of influenza causes the most flu cases worldwide

Influenza A

• It has a capsid that surrounds 8 single-stranded molecules of RNA

What is a capsid

A protein coat that encloses the nucleic acid in a virus

Define retrovirus

A group of viruses that have the ability to make DNA from RNA because they have reverse transcriptase

Outline HIV and what pathogen it’s caused by

• Caused by a virus

• It is an enveloped retrovirus

• The viral enzyme reverse transcriptase produces single-stranded DNA from its viral RNA

• DNA polymerase synthesises double-stranded DNA from this single-stranded DNA

• The double-stranded DNA is inserted into the host DNA and can remain inactive for many years

• Once activated the DNA provirus is used to synthesise new viruses

Are protoctista eukaryotes or prokaryotes?

• Protists are unicellular eukaryotes

Outline Potato Blight and what pathogen it’s caused by

• Caused by Protists

• The pathogen is unusual as it has some fungal characteristics

• It is transmitted via spores

• The first signs of potato blight are small, dark brown marks on the leaves which quickly increase in size and number

• The protist destroys potato and tomato crops leaving them completely inedible

How are fungi similar to plants?

• Their eukaryotic cells have cell walls and large central vacuoles

• However, instead of being made of separate cells, their bodies consist of filaments known as hyphae

• These hyphae form a network and spread throughout a host/soil

Outline Black Sigatoka and what pathogen it’s caused by

• Caused by fungi

• It spreads through the leaves of the plant, reducing its ability to photosynthesise

• The lack of photosynthesis causes parts of the leaf to die; producing black streaks

• Eventually, the whole leaf dies

Define disease transmission

• why can this be risky for pathogens

The transfer of pathogens from an infected host to an uninfected host

• During the infective stages, pathogens produce a large number of individuals to increase the likelihood that some will find a new host and survive - making it risky

How can spores be produced?

• Depending on the organism, spores can be produced via mitosis or meiosis so they can be haploid or diploid

What does the transmission of disease depend on

• Presence of pathogens in a population

• The presence of susceptible individuals

What are factors that affect disease transmission

Animals and plants can be resistant to some diseases

• Individuals who are resistant have mechanisms (coded by genes) that prevent the infection or spread of pathogens within their body

Resistant to different immunity

• An immune individual has been previously infected with the pathogen, suffered symptoms of the disease and recovered. They are highly unlikely to develop symptoms of the disease when exposed to the pathogen again

The proportion of resistant or immune individuals in a population

• he higher the proportion, the lower the probability of transmission