These questions cover some of the A Level BIology content that would be helpful for you to know before starting the course. Don’t worry if you are not sure of anything, this is just a revision exercise for you to use over the summer before university. All topics will be covered during lectures.

 

Looking for the answers? These are taken from past A Level exam papers so all answers are available online. Try and work them out first though!!

 

Cell Biology

• Cells that secrete enzymes contain a lot of rough endoplasmic reticulum (RER) and a large Golgi apparatus. Describe how the RER is involved in the production of enzymes.

• Describe how phospholipids are arranged in a plasma membrane.

• The figure below shows some cells from an onion root tip at different stages of the cell cycle. Name and order each stage:

 

 

 

 

 

 

 

 

 

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• Describe how crossing over occurs during meiosis.

 

Structure and Function

• When first hatched, the young of some species of fish are less than 2 mm long.Explain how these young fish get enough oxygen to their cells without having gills.

• Arteries and arterioles take blood away from the heart. Explain how the structures of the walls of arteries and arterioles are related to their functions.

• The pressure of the blood in an artery was measured during a cardiac cycle. The minimum pressure was 9.6 kPa and the maximum pressure was 13.4 kPa. Describe how the increase in pressure of the blood in the artery results from the events in the cardiac cycle.

• The elastin fibres in the wall of the artery help to smooth out the flow of blood. What happens to these fibres as the pressure of the blood in the artery changes?

 

Genetics

• Not all genetic mutations result in a change to the amino acid sequence of an encoded polypeptide. Explain why.

• A mutation of a tumour suppressor gene can result in the formation of a tumour. Explain how.

• Messenger RNA (mRNA) is used during translation to form polypeptides. Describe how mRNA is produced in the nucleus of a cell.

• Clostridium difficile is a bacterium that is present in the gut of up to 3% of healthy adults and 66% of healthy infants. C. difficile rarely causes problems, either in healthy adults or in infants. This is because its numbers are kept low by competition with harmless bacteria that normally live in the intestine. Use this information to explain why some patients treated with antibiotics can be affected by C. difficile.

 

Biodiversity

• Species richness and an index of diversity (E.g. Simpson's diversity index) can be used to measure biodiversity within a community. What is the difference between these two measures of biodiversity?

• The Amazonian forest today contains a very high diversity of bird species. Over the last 2 000 000 years, long periods of dry climate caused this forest to separate into a number of smaller forests. Different plant communities developed in each of these smaller forests. Each time the climate became wetter again, the smaller forests grew in size and merged to reform the Amazonian forest. Use the information provided to explain how a very high diversity of bird species has developed in the Amazonian forest. Speciation is far less frequent in the reformed Amazonian forest. Suggest one reason for this.

• Organisms can be classified using a hierarchy of phylogenetic groups. Explain what is meant by 'a hierarchy' and 'a phylogenetic group'.

• Explain what is meant by monoculture. Monoculture often involves the use of large amounts of pesticides. Some of these pesticides are toxic to species that are not pests. These animals may be killed immediately when the pesticide is applied. Explain one other way by which the use of pesticides can lead to the death of animals that are not pests.