Module 7 Revision

Disease can be defined as:

• any process that adversely affects the normal function of living things.

• only processes that involve pathogens and their effect on living things.

• only processes that do not involve the action of a pathogen on a living thing.

• only processes that affect animals. Plants do not get diseases.

Answer explanation

All plants and animals are subject to both infectious and non-infectious diseases, which affect the normal functioning of tissues.

The likelihood of an organism developing an infectious disease relies on a balance between:

• the pathogenicity of the microbe.

• the defensive capabilities of the host organism.

• the numbers of pathogens involved.

• the pathogenicity of the microbe, the defensive capabilities of the host organism, and the number of pathogens involved.

Answer explanation

The likelihood of developing a disease relies on the balance between the capabilities of the host and pathogen. Overwhelming pathogen numbers can still cause infection in a host with a functioning immune system.

Pathogens can be broadly classified into which of the following groups?

• deadly and harmless

• microscopic and macroscopic

• bacteria and viruses

• those that live inside and outside the body

Answer explanation

The first and most useful division is microscopic vs macroscopic. Many can initiate disease both inside and outside of the body. There are more pathogen classes than simply bacteria and viruses.

All bacteria have which of the following features?

• They are prokaryotic and contain a peptidoglycan cell wall.

• They are eukaryotic and contain a cellulose cell wall.

• They are prokaryotic and contain a membrane-bound nucleus.

• They are eukaryotic and possess a polysaccharide capsule.

Answer explanation

Bacteria have no membrane bound organelles and their cell wall is distinguishable from a plant cell wall in that it has a different chemical composition. Not all bacteria have a polysaccharide capsule.

Fungal cells contain a cell wall composed of:

• cellulose.

• peptidoglycan.

• chitin.

• hyphae.

Answer explanation

Fungal cells have a cell wall composed of chitin. Bacteria have a peptidoglycan cell wall. Plants have a cellulose cell wall.

Protozoa show which of the following features?

• Unicellular or multicellular.

• Have a cell wall.

• Prokaryotic or eukaryotics.

• Unicellular, eukaryotic organisms that commonly cause disease.

Answer explanation

Protozoa are eukaryotes because they have membrane bound organelles. They do not contain a cell wall.

Macroparasites are visible to the naked eye. They include two major groups which can be classified as:

• endoparasites and ectoparasites.

• heartworm and roundworm.

• egg-laying and non-egg laying

• insects and worms.

Answer explanation

The most useful initial grouping is endo and ectoparasites. Parasites include more than just worms. All reproduce through some sort of egg-laying.

Viruses are characterised by which of the following features?

• They are cellular and contain an external protein coat called a capsid.

• They are not cellular and contain an external protein coat called a capsid.

• They can be seen clearly with a school light microscope.

• They contain membrane-bound organelles.

Answer explanation

Viruses are not cellular organisms. They can only be seen with an electron microscope.

You discover a pathogen that consists solely of abnormal proteins and without genetic material. This is most likely to be a:

• virus.

• bacteria.

• fungus.

• prion.

Answer explanation

Prions consist of protein and contain no genetic material, unlike other pathogens.

Transmission of pathogens between hosts requires:

• direct contact.

• vector transmission.

• a susceptible host.

• the mere presence of a pathogen.

Answer explanation

Transmission may be direct or indirect. Not all transmission is via a vector. The presence of a pathogen does not necessarily mean transmission will occur unless the host is susceptible in some form to the pathogen.