NESA Biology Causes of Infectious Disease

Direct contact transmission requires physical contact between an infected person and a susceptible person, not an intermediate organism like a mosquito.

Droplet transmission occurs when respiratory droplets from coughing or sneezing carry pathogens directly to a susceptible person, which does not involve a mosquito.

Airborne transmission involves pathogens traveling through the air over time and distance, rather than being delivered by a biting insect.

This order incorrectly starts with isolating the microorganism before first establishing its presence in diseased animals and absence in healthy ones.

This sequence is incorrect because it suggests isolating the microorganism before confirming it is exclusively found in diseased animals.

This order is incorrect because it places the re-isolation of the microorganism from the experimental animal before actually infecting the healthy experimental animal.

While Phytophthora is a major threat to many Australian native plants, it is not restricted to them and infects plants worldwide.

Phytophthora is a plant pathogen (a type of water mold) and does not infect animals.

Phytophthora specifically targets and infects plants, not animals.

While some pathogens have complex life cycles, this complexity does not inherently cause rapid evolution and can sometimes slow down the reproductive rate.

Although many pathogens have simple life cycles, simplicity alone does not drive rapid evolution; the speed of reproduction is the critical factor.

Long generation times would actually slow down evolution, as it takes more time for new mutations to arise and be passed on to subsequent generations.

The chytrid fungus does not primarily invade the lungs; it specifically targets keratinized tissues on the outside of the body.

While the fungus can infect the keratinized mouthparts of tadpoles, the primary cause of fatal disease in adult frogs is not the invasion of the mouth.

The pathogen does not invade internal organs like the kidneys; it is an external infection that affects the epidermis.

This is incorrect because viruses lack ribosomes and other cellular machinery, requiring them to hijack a host cell to synthesize proteins.

This is incorrect because viruses are acellular and do not have cell walls, which are structures typically found in bacteria, plants, and fungi.

This is incorrect because viruses lack both cell walls and ribosomes, as they are not true cells and rely entirely on host organisms for reproduction.

Crown gall is a bacterial disease, not a viral infection caused by a DNA virus.

Crown gall is caused by a bacterium, not an RNA virus.

Phytophthora is a genus of plant-damaging oomycetes (water molds) responsible for diseases like potato late blight, not crown gall.

Malaria is transmitted by Anopheles mosquitoes, not Aedes mosquitoes, which are known for transmitting diseases like dengue and Zika.

While malaria can be fatal to humans, it does not typically kill the mosquito host, as the Plasmodium parasite relies on the mosquito to complete its life cycle and spread.

The malaria pathogen infects the salivary glands of the mosquito, not the human. In humans, the infection targets the liver and blood.

A permeable barrier would allow substances, including pathogens, to pass through, which would not provide effective physical protection.

Plants do not possess an adaptive immune system and therefore cannot produce antibodies.

The third line of defence refers to the adaptive immune system (involving B and T cells), which is present in vertebrates but absent in plants.

Tuberculosis is caused by a bacterium (Mycobacterium tuberculosis), not a virus, and it primarily affects the lungs rather than the nervous system.

While tuberculosis does primarily affect the lungs, it is a bacterial infection, not a fungal disease.

Tuberculosis is not transmitted by a vector (such as a mosquito or tick); it is spread directly from person to person.

While crown gall disease is caused by bacteria (Agrobacterium tumefaciens), the galls themselves are not made of bacterial cells, but rather the plant's own cells.

Crown gall disease is a bacterial infection, not a fungal one, and the resulting galls are composed of plant tissue.

The disease is caused by a bacterium, not a protist, and the galls consist of the host plant's cells.

While temperature can influence viral replication rates within the host, climate change primarily alters the disease's distribution by impacting the vector's life cycle and habitat, rather than the virus itself.

Ross River virus is a viral pathogen, not a bacterial one, making this option factually incorrect.

Although human behavior may shift with climate, the primary driver of the virus's changing geographic distribution is the environmental impact on its mosquito vector, not human reproduction or activity.

Viruses are acellular and do not contain their own ribosomes or other organelles required for protein synthesis.

DNA stores genetic information and is transcribed into RNA, but it is not the machinery that performs the translation of proteins.

While viral DNA or RNA provides the genetic blueprint for the viral proteins, the actual translation process is carried out by ribosomes, not the nucleic acids themselves.