Blood

Human blood contains red blood cells and white blood cells. Different situations can cause changes in the numbers of these blood cells. The table shows some of these changes.

Explain why poor diet can cause a change in the number of red blood cells.

Suggest why athletes often live at high altitude before competing in a long distance race.

Explain how the change in the number of white blood cells during therapy for cancer could be a risk to the patient.

The diagram shows two samples of blood that have been separated using a machine called a centrifuge. The centrifuge separates the components of blood by their density. One sample comes from a person with normal blood. The other sample comes from a person with anaemia.

Suggest why the components of the normal blood sample have separated into different layers as shown in the diagram.

Compare the appearance of the normal blood sample with the appearance of the sample from the person with anaemia.

Explain a symptom of anaemia.

Suggest why adult females are more likely to have anaemia than adult males.

Plasma transports many molecules around the body.

Name a food molecule transported in the plasma.

Name a non-food molecule transported in the plasma.

Components of blood have different functions.

Complete the table by giving the missing information.

When a person is vaccinated, their immune system produces memory cells. Describe the role of memory cells.

Chemotherapy is often used to help people with cancer. Chemotherapy kills cancer cells but may affect haemoglobin production in the body. A drug called EPO increases haemoglobin production in the body. Scientists investigated the effect of EPO on patients who had received chemotherapy. They injected EPO into these patients and blood samples were taken for several months to measure their haemoglobin levels. The table shows the results.

Plot a line graph to show the relationship between time and average haemoglobin level. Use a ruler to join the points with straight lines.

Name the dependent variable in this investigation.

Explain how the scientists made sure their results were reliable.

The scientists controlled biotic (living) factors so their results would be valid. Name two biotic factors that the scientists should have controlled.

Cancer patients often complain of tiredness after chemotherapy. Explain how EPO helps to reduce tiredness in these patients.

The scientists obtained blood samples using a needle attached to a syringe. Explain which type of blood vessel they should use to obtain the blood samples.

The passage describes some of the roles of components found in human blood. Complete the passage by writing a suitable word or words in each blank space.

The body uses white blood cells to combat infection. One type of blood cell ingests invading

bacteria and are called_........ . After ingesting bacteria they

produce_........ that digest the bacteria breaking them down.

Other white blood cells are called_........ and they release

specific molecules that bind to antigens on the surface of the pathogen.

Other components of the blood are also involved in helping wounds to heal.

Small cell fragments called platelets help the blood to_........ .

This seals the wound to prevent further_........ and prevent

The diagram shows part of a food web in an oak forest.

Use the information in the food web to complete the statements in the table. The first one has been done for you.

What effect would a decrease in the population size of caterpillars have on the population size of blue jays?

What is meant by the term population ?

The tick feeds on deer by sucking their blood. Name two different molecules that are found in the blood of deer that the tick could feed on.

The diagrams show sections through an artery and a vein.

Use the information in the diagrams and your own knowledge to give three ways in which the structure of an artery differs from the structure of a vein.

Lack of movement by sitting still for long periods of time makes blood flow very slowly in a vein. Blood that flows slowly is more likely to clot than blood that flows normally. This problem is known as deep vein thrombosis (DVT). In DVT, the clot usually occurs in a leg vein as shown in the diagram.

DVT is dangerous because sometimes part of the clot breaks off and travels to the lung, blocking small blood vessels and causing death.

Suggest why blood flow in a leg vein is slow when there is lack of movement.

Name the blood cells responsible for transporting oxygen.

Suggest why a clot that blocks the small blood vessels in the lungs can cause death.