IB Biology HL C3.2 Defence Against Disease Questions

Pathogens are disease-causing organisms.

State two of the body's primary defences to pathogens.

Plasma proteins, sCD 62 P and sCD 40 L , are involved in the activation of blood platelets. The von Willebrand factor causes the platelets to stick to blood vessel walls. Fibrinogen is a marker for inflammation of the blood system. All four are biological markers that indicate a risk of thrombosis.

During the 2008 Olympic games held in Beijing, the Chinese authorities temporarily reduced air pollution levels by restricting emissions from motor vehicles and industry. Doctors used this event to test the effects of air pollution on these biological markers. The graph shows the mean percentage changes in the levels of biological markers in volunteers during the study.

Thromboses, including coronary thrombosis, could be a consequence of a build-up of these biomarkers.

State the role of platelets in thromboses.

Adaptive immunity leads to cells that are infected by viruses being killed, resulting in immune memory which is the basis of vaccination.

Distinguish between innate and adaptive immune response.

The graph shows the magnitude of the immune response after infection or after vaccination over time.

What action(s) can phagocytes perform?

I. Make antibodies
II. Leave the blood stream and enter infected tissues
III. Kill pathogens that they have engulfed

Multicellular organisms benefit from cell specialization and division of labour.

Explain how cells in the bloodstream cause a specific immune response.

What describes antigens?

Ebola virus disease (EVD) is the disease in humans and other primates that is caused by the Ebola virus. Fruit bats are the reservoir for the virus and are able to spread the disease without being affected. Humans can become infected by contact with fruit bats or with people infected by the virus, their body fluids or equipment used to treat them.

The stacked bar graph shows the epidemiological data for the EVD cases in Conakry, the capital city of Guinea, surrounding suburbs and rural areas in Guinea from the beginning of January 2014 to the end of March 2015.

Explain how vaccination can lead to the production of B cells specific to the Ebola virus.

The figure shows a transmission electron micrograph of rotavirus particles. Each rotavirus is about 70 nanometres in diameter.

State the role of plasma cells in the immune system.

The black-legged tick (Ixodes scapularis) is an arthropod which sucks blood from humans and other mammals. It is encountered mainly in wooded and semi-wooded areas.

Some ticks can be infected by the bacterium Borrelia burgdorferi. When a tick bites a human, the bacterium is often introduced, causing Lyme disease. Lyme disease is a public health problem in North America and, if left untreated, can cause important neurological impairment. The diagram represents the two-year life cycle of a tick.

White-footed mice (Peromyscus leucopus) in eastern North America's wooded areas often host B. burgdorferi bacteria. To determine whether bacterial transmission from mice to tick nymphs could be prevented, mice were vaccinated with antigens from Lyme disease-causing B. burgdorferi. Scientists captured wild mice at two different sites in the woods once a month, over 4 months. Each time, they measured the levels of antibodies to B. burgdorferi present in the captured and re-captured mice, inoculated all of them, and released them into the woods. The control group was not vaccinated with B. burgdorferi antigen.

Suggest possible reasons for the observed pattern of presence of antibodies in vaccinated mice.

The summer after vaccination, the prevalence of B. burgdorferi infection in tick nymphs collected on mice from the two sites was measured.

How has the transmission of HIV been reduced?

Interactions in biological systems may have harmful or beneficial effects.

Discuss the consequences of infection with HIV.

The figure shows a transmission electron micrograph of rotavirus particles. Each rotavirus is about 70 nanometres in diameter.

Rotavirus causes diarrhea and vomiting. Explain why viral diseases cannot be treated using antibiotics.

Different strains of the bacterium Enterobacter cloacae were grown on a plate and identified according to their place on the plate (for example, the first strain top left is A1). They were then transferred to Petri dishes containing agar with varying concentrations of antibiotic $\left(5,10,20,40,80,160 \mu \mathrm{gml}^{-1}\right)$.

The Petri dishes were left for 24 hours in an incubator at $25^{\circ} \mathrm{C}$ and the resulting plates are shown.

The table shows the number of amino acids that are different in the sequences of the protein FOXP2 from a human compared with four other primate species.

Some infectious diseases in humans are caused by viruses that originated in other primates.

State the term used for an infectious disease that can transfer from other species to humans.

Some prokaryotes cause infectious disease in humans. Explain the principles of vaccination.

For a pathogen transmitted between people, immunity substantially reduces the chance that an exposed person becomes infectious. In a population with widespread immunity, even a susceptible individual can have a reduced chance of exposure.

What explains this indirect protection?