OCR GCSE Combined Science B (21st Century) Paper 1 November 2020 question paper

DNA is a long-chain molecule, which is made from smaller molecules called amino acids / nucleotides / sugars.

These smaller molecules join to form a monomer / polymer / protein.

Two strands of DNA form a double / single / triple helix.

The method for using a light microscope to see a sample of cells is shown below, but is not in the correct order.

A A higher power objective lens is selected and used to focus the image.

B A stain is added to the cells.

C The cells are squashed into a thin layer on the slide.

D The lowest objective lens is selected and used to focus the image.

E The prepared slide is placed on the microscope stage.

Write the letters in the boxes to give the correct order for the method.

The first one has been done for you.

A student calculates the length of a plant and animal cell using a light microscope.

The length of the plant cell is 100 m. The length of the animal cell is 25 m.

How many times bigger is the plant cell compared to the animal cell?

2500 40 4 0.25

Animal cells are approximately 10 times bigger than bacterial cells.

Which statement about order of magnitude for animal cells and bacterial cells is true ?

Tick (✓) one box.

DiGeorge syndrome is a genetic disorder caused by the deletion of a small part of chromosome 22.

A genetic test can be used to show if babies have this disorder.

Some friends are discussing if babies should be genetically tested for DiGeorge syndrome soon after they are born.

Which friend is considering risk?

Which friend has a concern that should be answered by government and society?

Which friend is thinking about ethical issues?

Give one other example of when a genetic test could be used.

679 106 babies were born in the UK in 2017.

It is estimated that 1 in every 2000 babies are born with DiGeorge syndrome.

Calculate the expected number of babies born in 2017 with DiGeorge syndrome.

Give your answer to the nearest whole number.

Scientific discoveries are often reported in newspapers.

Why is it important that scientific discoveries are reported in newspapers?

Tick (✓) two boxes.

Suggest three lifestyle factors which can affect good health.

A population of Salmonella bacteria reproduce approximately every 30 minutes.

Calculate how many Salmonella bacteria will be present after four hours, when starting with one bacterium in the population.

Assume no bacteria have died.

Salmonella infections can be treated with antibiotics.

Which two statements explain why doctors do not usually give antibiotics to people infected with Salmonella bacteria?

Tick (✓) two boxes.

A researcher tested the effectiveness of three different concentrations of antibiotic on the growth of Salmonella bacteria.

Paper discs were soaked in each antibiotic and then placed on an agar plate which was covered in the Salmonella bacteria. One other paper disc was soaked in sterile water as a control disc.

The clear zones are where the bacteria did not grow. The results are shown in Fig. 3.2.

Which concentration of antibiotic, A, B, or C, was the most effective?

Calculate the cross-sectional area of the clear zone (including the area of the disc) for the most effective concentration of antibiotic.

Use a clear zone diameter given in Fig. 3.2.

Use the formula: r²

= 3.14

Drug companies are trying to develop new medicines.

The four stages in the testing of a new medicine are given below, but are not in the correct order.

A Animal testing

B Healthy human volunteers

C Cultured human cells

D Human volunteers with disease

Write the letters in the boxes to give the correct order of the stages for the testing of new

Which stage, A, B, C or D, only assesses the safety of the new medicine?

Shorthorn cattle were kept by 18th century farmers as they produced both meat and milk.

By the 20th century, farmers used selective breeding to produce two types of shorthorn cattle:

Type A – cattle that produced a large quantity of good quality meat, but produced little milk.

Type B – cattle that produced poor quality meat, but lots of milk.

Describe how farmers used selective breeding to produce type A shorthorn cattle.

In the 18th century the human population of the world was approximately 1 billion. The human population of the world now is approximately 8 billion.

Suggest two ways in which selective breeding has helped humans.

Coat colour in cattle is controlled by genes.

A red cow and a black bull reproduce. The coat colour of the offspring is black, as shown in Fig. 4.1.

The dominant allele for coat colour is black.

Write down the genotype of a homozygous red cow and a homozygous black bull.

Use B to represent the black allele and b to represent the red allele.

Genotype of red cow........

Genotype of black bull........

When a homozygous red cow and a homozygous black bull (first generation) are mated all of the offspring (second generation) are black with the genotype Bb.

If the offspring of homozygous red cows and homozygous black bulls (second generation) breed, some of the offspring in the third generation are black and some are red.

Complete the Punnett square to show the expected percentage of black cattle and red cattle in the third generation.

Cows are used in conservation grazing to help prevent grassland turning into woodland. This helps maintain biodiversity.

Draw lines to connect each cow behaviour with how the behaviour helps maintain biodiversity.

Cow behaviour
How behaviour helps maintain biodiversity

The circulatory system moves substances around the body.

The blood vessels, A, B, C and D, in Fig. 5.1 each carry different compositions of blood.

Identify which blood vessel carries which blood composition. Tick (✓) one box in each row.

Explain how the structure of the heart is adapted to pump blood around the body.

* Some babies are born with a hole in the heart.

Fig. 5.2 show a cross-section of normal heart and a heart that has a hole in it.

Suggest how the hole in the heart will change the circulation of blood and how this will affect the cellular activity in the baby.

Blood transports many substances around the body.

Complete the table to show whether each substance is transported in the blood by the plasma or by the red blood cells.

Tick (✓) one box in each row.

The diagram shows two views of a red blood cell.

Explain how the shape of a red blood cell is adapted to its function.

Two transport tissues are found in plants.

Name the transport tissue that transports water and minerals.

Name the transport tissue that transports sugars.

The sugars that are made by photosynthesis move into a transport tissue to go to the rest of the plant.

Which process moves sugars into the transport tissue?

Active transport Respiration Osmosis Transpiration

A student uses a microscope to count the number of stomata in a field of view.

The student counts the number of stomata in three other fields of view, and his results are shown in the table.

Calculate the mean number of stomata per field of view.

Use the data in the table.

Some of the sugars that are made by photosynthesis are joined together to make a large storage molecule.

What is the name of this large storage molecule?

Tick (✓) one box.

Amaya feeds birds in her garden.

She wants to see if there is a relationship between the body mass of the bird and how often they are feeding.

Amaya records how often she sees each bird species feeding and produces a dominance rank, as shown in the table.

The highest ranked species, the house sparrow, is seen feeding the most.

She finds out the mean body mass for each bird species from doing some research.

Complete the table by rounding the mean body mass of each bird species to the nearest

whole number.

Plot a graph of dominance rank against rounded body mass, using the data in the table.

Draw a line of best fit.

Before Amaya collected the data, she wrote the following hypothesis:

The greater the mass of the species of bird, the more often the species will feed.

Do Amaya’s findings support her hypothesis?

Use the graph to explain your answer.

Explain why Amaya’s findings do not prove her hypothesis.

The birds in Amaya’s garden are part of a community that includes plants and other animal species.

The species in this community are interdependent.

Give two reasons why this interdependence is important for the species in the community.

Complete the sentences to describe the process of photosynthesis.

Use words from the list.

You may use the words once, more than once or not at all.

carbon dioxide chlorophyll energy glucose

light oxygen protein respiration

starch transpiration water

Photosynthesis has two main stages. The first stage requires light and

........ to split water molecules into hydrogen and the waste product

........ Some of the waste product is used for........ by

the plant, and the excess is released from the leaves. The hydrogen is transferred to the

second stage.

In the second stage carbon dioxide and hydrogen combine to make........

The process of photosynthesis is endothermic, and endothermic processes require transfer

of........ from the surroundings.

A student is investigating the requirements of photosynthesis.

The student sets up three tubes, Tube A, Tube B, and Tube C as shown in Fig. 9.1, and leaves them for 24 hours in a room with windows.

Light-proof cover
Non-poisonous indicator

Table 9.1 shows the indicator colour changes when the carbon dioxide level changes.

Table 9.2 shows the colour of the indicator at the start, and at the end after 24 hours, for each tube.

Which tube, A, B or C, shows that carbon dioxide is needed for photosynthesis to occur?

Explain your answer.

Tube........

Explanation

Which tube, A, B or C, shows that light is needed for photosynthesis to occur?

Explain your answer.

Tube........

Explanation

Explain why the indicator in Tube C does not change colour.

Identify one variable that should be kept the same in the student’s investigation.