Set B (AQA GCSE Biology): Exam Questions

The Bering Strait is a narrow passage of the Pacific Ocean that separates Asia from North America.

At its narrowest, the strait is 82 km across.

It is generally accepted that when sea levels were lower in the past, a ‘land-bridge’ in the strait was exposed, allowing animals to migrate from Asia to North America, and vice versa. When sea levels rose, the land-bridge disappeared.

Explain how the emergence and disappearance of a land-bridge could have fuelled speciation.

Even though nylon wasn't invented until the 1940s, bacteria were soon isolated that could degrade nylon.

The bacterium Paenarthrobacter ureafaciens has special enzymes that allow it to metabolise nylon and use it as a sole energy source.

This is a very simple example of natural selection.

Describe how organisms can evolve through the process of natural selection.

Higher Tier Only

The menstrual cycle is regulated through the action of several hormones. 

Figure 1 shows the changes in hormones oestrogen and progesterone over the 28 day period of the menstrual cycle. It also shows the changes that occur in the uterus lining throughout that time.

Figure 1

Explain the reasons for the decrease in the thickness of the uterus lining shown between days 0 and 3 in Figure 1.

Higher Tier Only

Describe and explain the relationship between the concentration of oestrogen in the blood and the thickness of the uterus lining between days 7 and 14.

Higher Tier Only

Figure 1 shows that progesterone levels remain high between days 14 and 27 of the cycle and then start to decrease around day 28. However, if an egg is fertilised, the concentration of progesterone does not follow the pattern shown in Figure 1.

Use your knowledge of hormones in human reproduction to describe how the concentration of progesterone would be affected by fertilisation and explain why it is affected in this way.

Reproductive hormones are responsible for the start of puberty.

Describe the changes that result from the onset of puberty. 

Extremophiles are (most commonly) microorganisms; these are adapted to live in extreme chemical or geophysical conditions. 

In some cases, scientists attempting to discover the genetic composition of extremophiles have struggled to break open their cells in an attempt to isolate their DNA.

Suggest why it has been difficult to access the DNA of certain extremophiles for research purposes.

Figure 1 is a sketch graph showing the effect of increasing temperature on the activity of a typical human enzyme.

Figure 1

The thermophilic microorganism Methanopyrus kandleri thrives at temperatures around 120°C

Sketch a line on the graph in Figure 1 to show the effect of increasing temperature on the activity of an enzyme from Methanopyrus kandleri.

Certain thermophilic bacteria are known as obligate thermophiles.

Select A - D which best defines the term 'obligate thermophiles'.

Thermophilic organisms have been used in the following processes

• The manufacturing of biological washing powder

• The degradation of pollutants

• Bioremediation of oil-contaminated soil in the desert

• Removal of heavy metals in the soil

• The conversion of biomass to biofuels

• The degradation of toxic textile dyes

Explain why thermophilic bacteria are chosen for these roles over bacteria that are adapted for life at more moderate temperatures. 

Red-green colour blindness is a genetically inherited condition that causes individuals with the condition to not be able to distinguish between certain colours. 

Red-green colour blindness is caused by a recessive allele located on the X chromosome. 

In order for a male to have the condition they only need to inherit one copy of the recessive allele on the X chromosome, whereas a female needs to inherit two copies of the recessive allele. 

Why is this the case?

Using Figure 6, explain why it is possible for the X chromosome to have genes that are not found on the Y chromosome. 

Figure 6

Higher Tier Only

A heterozygous woman and a colour blind man want to have a child.

Draw a Punnett square diagram to determine the probability of the child having colour blindness

Identify any children with colour blindness.

Use the following symbols:

X^B = dominant allele on the X chromosome

X^b = recessive allele on the X chromosome

Y = Y chromosome (no colour blindness allele)

Offspring genotypes: _____________________________________________

Offspring phenotypes: ____________________________________________

In humans 8 % of males and 0.6 % of females of Northern European ancestry suffer from red-green colour blindness. 

A sample of people with Northern European ancestry was surveyed; the sample included 5 000 000 males and 5 000 000 females.

Calculate how many more men from this sample suffer from red-green colour blindness than women. Give your answer in standard form.

Figure 7 shows the path of light entering the front part of the eye of a person with normal vision, whilst looking at a close object.

Figure 7

As people get older (typically 40+), their lenses lose flexibility and can't spring back into a round shape when looking at close objects.

Explain what effect a less flexible lens would have on the path of light. 

Explain the changes that occur in the normal human eye to focus on near and distant objects.

Explain why long-sighted people are unable to focus on near objects and how this can be corrected using glasses.

As people age, their vision tends to deteriorate. The majority of adults choose to wear glasses to correct their vision as shown in Figure 8.

Figure 8

Explain how laser eye surgery can correct a person's eyesight and suggest a reason why it is not as popular as other methods of vision correction.

Table 2 gives data about how the carbon dioxide (CO₂) concentration of the air has changed over time. 

Plot the data from Table 2 in the graph paper provided below. 

Explain why carbon dioxide concentrations in the atmosphere are changing.

In 2022, a climate activist claimed that, to arrest global warming, the atmospheric CO₂ level should be brought back to the level of the year 1900.

Using the data from Table 2, calculate the percentage decrease that the climate activist claims would be needed to return the atmospheric CO₂ level to its 1900 level. 

Figure 3 shows some damage to a piece of furniture caused by woodworm. 

Figure 3

State how the action of woodworm can contribute to global warming. 

Figure 4 shows when four different equine species existed. 

Figure 4

Determine the number of years both Hypohippus and Merychippus existed together.

Using Figure 4, state when the Equus first evolved. 

By viewing the fossil record of these species scientists can get a better understanding of the way that the modern day horse evolved. 

Information about extinct animals is often not clear because the fossil record is incomplete.

Give three reasons why the fossil record is not clear for older species.

Horse evolution is well documented in the fossil record. 

There are many species where gaps in the fossil record make it difficult to understand how they evolved. 

For example, it is difficult to trace the evolution of soft bodied invertebrates using the fossil record. 

Describe how soft bodied invertebrates can be fossilised and explain why we know a lot less about the evolution of soft bodied invertebrates compared to the evolution of horses. 

Higher Tier Only

Figure 2 shows the blood glucose levels of a healthy individual.

Explain the events that most likely occur at points A to D.

Figure 2

The insulin receptor (INSR), is a transmembrane receptor that is activated when insulin binds to it. The binding of insulin triggers a signalling pathway that activates glucose transporters in the cell membrane. 

Some people suffer from a mutation in the INSR gene. 

Suggest the effect of such a mutation. 

A scientist was interested in finding out how much water was lost from the human body on a particular day.

They measured the volume of fluid consumed and the volume of urine excreted.

Explain why measuring the volume of urine excreted would not be an accurate assessment of water lost.