OCR A Level Biology A Biological Diversity June 2023 question paper H420/02

Which option correctly describes a tissue?

A A group of cells performing similar functions

B A group of organs performing a specific function

C A group of similar cells performing a specific function

D A group of similar cells performing a variety of functions

Bone marrow stem cells are a source of erythrocytes.

Which statement about bone marrow stem cells and their role in the production of erythrocytes is correct?

A Bone marrow stem cells are totipotent and can therefore differentiate into any type of cell.

B Erythrocytes are the only blood cell produced from bone marrow stem cells.

C Erythrocytes need to be replaced from bone marrow stem cells because erythrocytes are unable to undergo mitosis.

D In humans, differentiation of bone marrow stem cells into erythrocytes involves the synthesis of a haploid nucleus.

Which option correctly describes the sequence of events during the cell cycle?

Scientists crossed two plants that were heterozygous for two different genes. Both plants had the same genotype, AaBb.

The genotypes and ratios of the offspring resulting from this cross were:

AABB AaBb aabb

1: 2: 1

Which option could explain these observations?

A Autosomal linkage

B Crossing over

C Epistasis

D Mutation

A student was observing and measuring cells using a light microscope.

Which option describes a method that would enable the student to accurately measure the length of a cell?

A View the cells using a calibrated eyepiece graticule and note the magnification of the eyepiece lens.

B View the cells using a calibrated eyepiece graticule and note the magnification of the objective lens.

C View the cells using a stage micrometer and note the magnification of the eyepiece lens.

D View the cells using a stage micrometer and note the magnification of the objective lens.

Which of the following describes, from lowest to highest, the resolution of images than can be achieved by different types of microscope?

A Light microscope scanning electron microscope transmission electron microscope

B Light microscope transmission electron microscope laser scanning confocal microscope

C Light microscope transmission electron microscope scanning electron microscope

D Scanning electron microscope transmission electron microscope light microscope

Lactose metabolism in E. coli is controlled by the lac operon.

Which of the structures associated with the lac operon contain nucleic acids?

1: the operator 2: the regulator gene 3: the structural gene product

A 1, 2 and 3

B Only 1 and 2

C Only 2 and 3

D Only 1

Homeobox genes control body plan in eukaryotes.

Which of the statements about homeobox genes are correct?

1: they bind to transcription factors 2: they contain a highly conserved sequence of 180 base pairs 3: they regulate the expression of structural genes

A 1, 2 and 3

B Only 1 and 2

C Only 2 and 3

D Only 1

The graph below shows the population of viable bacteria in a flask over 48 hours.

Which time, A to D, has the highest bacterial death rate?

The image below shows representations of the structures of four polysaccharides.

Use the image to answer questions 10 and 11.

Which of the molecules contains the highest proportion of 1-6 glycosidic bonds?

A Amylopectin

B Amylose

C Cellulose

D Glycogen

The image below shows representations of the structures of four polysaccharides.

Use the image to answer questions 10 and 11.

Which of the molecules is not used for energy storage?

A Amylopectin

B Amylose

C Cellulose

D Glycogen

The modern pedigree dog breeds have been produced by many years of selective breeding.

Which option does not explain why genetic disorders are common in pedigree dogs?

A Characteristics that are desirable to humans can be associated with features that are harmful to dogs.

B Selective breeding increases the chance of an individual being homozygous for certain characteristics.

C Selective breeding increases the chance of mutations.

D Selective breeding is associated with inbreeding depression.

What step could be taken to reduce the occurrence of genetic disorders in pedigree dogs?

A Breeding only with individuals that meet the official breed descriptions.

B Broadening the official descriptions of pedigree dog breeds.

C Increased use of somatic gene therapy.

D Regular cross-breeding with the wild ancestor of domestic dogs.

Organisms are named using the binomial system.

What is the correct way to represent the binomial name for domestic dogs?

A Canis familiaris

B Canis familiaris

C canis familiaris

D canis familiaris

The image below shows an enzyme and its substrate.

Enzyme Substrate

Which option represents a coenzyme for this enzyme?

Many organisms undergo asexual reproduction by mitosis.

State two other roles of mitosis in organisms.

Plants reproduce asexually by mitosis.

Explain why mitosis, and not meiosis, is used for asexual reproduction in plants.

Bacteria reproduce asexually by a process called binary fission.

Suggest why bacteria are unable to reproduce asexually by mitosis.

During meiosis, the independent assortment of chromosomes leads to the formation of genetically different gametes.

Gametes of the western clawed frog contain 10 chromosomes.

Calculate the number of genetically different gametes resulting from the independent assortment of chromosomes that would be produced by an individual frog.

State the independent variable in this investigation.

Describe how a student could produce an 8 a.u. solution from a 20 a.u. stock solution.

Liver tissue contains a higher concentration of catalase than potato.

Suggest two reasons why the students chose potato rather than liver as a source of catalase.

The potato cylinders were cut to equal lengths.

Suggest a further precaution the students should have taken when preparing them, to ensure the investigation was valid.

Calculate the standard deviation for the 60 s result at 20 a.u. hydrogen peroxide.

Use the standard deviations to discuss the repeatability of the students’ results.

The students calculated the initial rate of reaction over the first 30 s.

Calculate the rate of reaction over the first 30 s for the result at 2 a.u. hydrogen peroxide.

When analysing the results, the students assumed that the volume of oxygen collected was the same as the volume of oxygen produced from breakdown of hydrogen peroxide.

Suggest two reasons why the value the students recorded for volume of oxygen collected might not accurately reflect the volume of oxygen produced.

Fig. 17.2 shows a graph of the students’ results.

Fig. 17.2

Explain the results for 20 a.u. hydrogen peroxide.

State one other method for immobilising enzymes.

One advantage of using immobilised enzymes is that the enzyme can be reused many times. However, the process of immobilisation can reduce the activity of enzymes.

With reference to Fig. 18.1, explain why the activity of immobilised enzymes might be lower than that of enzymes that are free in solution.

Invertase is an enzyme that catalyses the following reaction:

Invertase is present in cells of baker’s yeast, a type of fungus.

It is possible to immobilise invertase and it is also possible to immobilise yeast cells.

Suggest one reason why using immobilised yeast might be more expensive than using immobilised invertase.

Animals are protected from infectious diseases by their immune system.

Influenza is a viral disease that is common in winter months. It is transmitted when an uninfected person inhales droplets of moisture that an infected person has exhaled, often when coughing or sneezing.

Explain how mucous membranes make it more difficult for the influenza virus to enter the body.

Antigens on the surface of pathogens can provoke an immune response in a patient.

Fig. 19.1 shows the changes in antibody concentration in the blood of a patient.

Fig. 19.1

Different events during these immune responses have been represented as areas on the graph labelled with letters, A to F.

Complete the table with a letter or letters to indicate where on the graph the event is

Fragments of antibodies, known as Fab fragments, have a number of uses.

Snakebites can be treated using Fab fragments.

Antibodies specific to the snake venom are produced using donor animals, usually sheep. These antibodies are collected from the animal’s blood and then digested to produce Fab fragments. The patient can be injected with these fragments after being bitten by a snake.

Name the type of immunity this treatment gives the patient.

Fig. 19.2 shows the structure of a Fab fragment.

Fig. 19.2

Identify two similarities and one difference in structure between a Fab fragment and a whole antibody.

Infectious disease caused by pathogenic bacteria can be treated using antibiotics. The first antibiotics became widely available in the middle of the 20^th Century.

Explain why many varieties of pathogenic bacteria are now resistant to a range of antibiotics.

Plants and microorganisms have traditionally been used as sources of new medicines.

Synthetic biology could play a major role in the development of new medicines.

Outline how synthetic biology can be used in the provision of new medicines.

Grey wolves became extinct in an area of North America in the 1920s. In 1993 some grey wolves were reintroduced into the same area.

Grey wolves feed mainly on large herbivores, such as deer.

The graph shows the population of grey wolves and some other species since the reintroduction.

Describe the changes in the deer population since 1993.

Calculate the percentage increase in the wolf population between 1995 and 2003.

Between 2003 and 2010 there were no significant changes in the climate of this area of North America and no disease outbreaks.

Suggest and explain one reason for the changes in the grey wolf population since 2003.

Beavers are mammals that live in water. They form colonies nesting under big mounds of wood set as islands in areas of water.

In 1993 there was one colony of beavers living in the area to which the wolves were reintroduced.

Suggest why the population of beavers is measured in colonies rather than individual animals.

Scientists have claimed that the reintroduction of the wolves has caused the beaver population to increase.

Evaluate the support given by the evidence in the graph for the scientists’ claim.

Beavers build dams in the water using trees they have cut down. Deer damage trees while they are feeding. Wolves often hunt deer that are feeding near water.

The following explanation for the increase in beaver population has been suggested by scientists:

• The presence of wolves causes deer to avoid grazing close to water.

• This means that trees near water are not damaged.

• Beavers have a plentiful supply of trees with which to build dams.

Suggest one other piece of useful evidence that could be measured that would support the scientists’ claim.

Beavers are a species that was once native to Britain. The species became extinct in Britain about 400 years ago.

In 2009, a population of beavers was brought from Norway and released into the wild in Britain.

Explain why the reintroduction of beavers to Britain is an example of conservation.

Suggest a situation in which preservation of a habitat would be necessary.

The element nitrogen is recycled within ecosystems.

Complete the sentences using the most appropriate terms.

When animals die microorganisms convert nitrogen-containing molecules in the animals’

bodies to ammonia in a process known as........ This ammonia is

converted into nitrites and nitrates by........ bacteria. The bacterium

........ converts ammonia to nitrites and the bacterium........

converts nitrites to nitrates. Nitrates can be absorbed by plants and converted to

........ Nitrogen gas is very unreactive but it can enter the nitrogen cycle by

being converted to ammonia by........ bacteria such as Rhizobium.

Use your knowledge of the nitrogen cycle to suggest and explain why plants do not grow well in soil with a low oxygen content.

Rhizobium forms nodules on the roots of certain plants. The Rhizobium receives a supply of glucose from the plant which the bacterium is able to use.

The diagram below shows an incomplete diagram of the structure of alpha glucose.

Write on the diagram to show the complete structure of alpha glucose.

Explain how the structure of glucose allows it to move from the plant to the bacterium.