Mucus traps pathogenic bacteria. Mucus also attracts viruses that attack pathogenic bacteria.

[Source: EYE OF SCIENCE/SCIENCE PHOTO LIBRARY]

What part of the immune system do these viruses resemble in their function?

A. Antigens

B. Antibodies

C. Memory cells

D. Antibiotics

The diagram shows the female reproductive system.

[Source: © International Baccalaureate Organization 2017]

Which structures do K and L identify?

The diagram shows a section through a seminiferous tubule.

[Source: © International Baccalaureate Organization 2020.]

Which labelled cells are diploid and haploid, respectively?

Outline how the muscle attachment of insects differs from humans.

The image shows part of a myofibril from a relaxed muscle fibre.

[Source: Sarcomere. Sameerb. Available at https://commons.wikimedia.org/wiki/File:Sarcomere.gif
[Accessed 30 November 2021].]

What occurs during muscle contraction?

A. Myosin binding sites are blocked.

B. The bands labelled Y get shorter.

C. The bands labelled X get shorter.

D. Calcium ions bind to myosin.

The micrograph shows a glomerulus and Bowman’s capsule, where ultrafiltration takes place in the kidney.

[Source: MICROSCAPE/SCIENCE PHOTO LIBRARY.]

What facilitates the formation of glomerular filtrate?

A. Many fenestrations in walls of capillaries in the glomerulus

B. High pressure in the Bowman’s capsule

C. ADH secreted by the pituitary gland

D. Osmosis caused by a high concentration of urea in the blood

The diagram shows a method for the production of monoclonal antibodies.

Which kidney adaptation would be expected in the desert kangaroo rat (Dipodomys deserti)?

A. Increased nephron density
B. Longer proximal convoluted tubule
C. Longer loop of Henle
D. Increased ADH receptors on the collecting duct

 

Label region X and structure Y on the diagram of the kidney.

[Source: PeterHermesFurian/iStock]

The diagram shows the chromosomes derived from a single homologous pair following meiosis in a diploid cell.

Which diagram represents the homologous pair from which these chromosomes were derived?

[Source: © International Baccalaureate Organization 2019]

The image shows a light micrograph of tissue stained with a dye that binds to the nucleic acids in a cell.

[Source: by Jose Luis Calvo/Shutterstock]

What is the major purpose of the tissue depicted in the image?

A. Absorption of digested food

B. Production of insulin

C. Spermatogenesis

D. Fertilization

Cell biologists play an important role in research into disease, fertility, evolution and many
other areas of science.

Compare and contrast the processes of spermatogenesis and oogenesis.

The electron micrograph shows sarcomeres in myofibrils of striated muscle during muscle contraction. The lines P–Q and R–S show two regions of one sarcomere.

[Source: Republished with permission of Elsevier - Health Sciences Division from Cell by Don W. Fawcett 1981 ; permission conveyed through Copyright Clearance Center, Inc.]

How would regions P–Q and R–S change when the muscle relaxes?

The micrograph shows part of a human sperm cell. Which region of the cell is responsible for the greatest production of ATP?

Explain the mechanism that prevents polyspermy during fertilization.

Describe the production of hybridoma cells.

The diagram shows a section through the seminiferous tubules. What is the cell labelled X?

[Source: © International Baccalaureate Organization 2019]

A. Spermatid that will differentiate into sperm

B. Primary spermatocyte that will undergo meiosis to form secondary spermatocytes

C. Sertoli cell that provides nutrients

D. Stem cell that will divide by mitosis to form spermatogonia

A hybridoma is a cell produced by the fusion of a plasma cell with a tumour cell. Explain the advantages of using hybridoma cells in the production of monoclonal antibodies.

Suggest how the graph would differ for a human during a long period of inactivity.

Explain how water balance is restored in mammals when they are dehydrated.

Describe how monoclonal antibodies are produced.

Humans need to balance water and solute concentrations and also excrete nitrogenous wastes. Explain how the different parts of the kidney carry out these processes.

Describe adaptations in mammals living in desert ecosystems to maintain osmolarity in their bodies.

Describe the role of ADH in human osmoregulation.

Explain the role of the kidney in osmoregulation.

Nitrogen is part of many important substances in living organisms.

Explain how insects excrete nitrogenous wastes.

The pregnancy test for humans is based on detection of the hormone HCG. What is the reason for detection of this hormone indicating pregnancy?

A. HCG is involved in milk production.

B. HCG production is blocked by negative feedback during menstruation.

C. HCG is produced by an embryo.

D. HCG is released during the acrosome reaction.

The graph shows three hormones circulating during pregnancy in the rat, with birth occurring at 22 days.

[Source: Dr Paul Kenyon University of Plymouth (retired).]

What are hormones X and Z?

The salt marshes where these turtles live periodically dry up to small pools. Discuss the problems that this will cause for nitrogen excretion in the turtles and how their behaviour might overcome the problems.

Where in the nephron is most glucose reabsorbed?

[Source: National Institute of Diabetes and Digestive and Kidney Diseases, n.d. [Nephron]. [diagram online] Available at:
https://www.niddk.nih.gov/news/media-library/9164 [Accessed 23 March 2020].]

The diagram shows structures involved in contraction of a sarcomere.

Plasma cells secrete antibodies against specific antigens. Outline how plasma cells become activated.

State one use of monoclonal antibodies.

What function is maintained as a result of the release of HCG?

A. Production of milk by the mammary glands

B. Release of oxytocin by the posterior pituitary gland

C. Production of FSH by the anterior pituitary gland

D. Production of progesterone by the ovary

Outline the roles of estrogen and progesterone in females during human reproduction.

The diagram represents a sarcomere. Which structure is myosin?

[Source: MPI of Molecular Plant Physiology. [Sarcomere]. [diagram online] Available at: http://www.macroevolution.net/sarcomere.html [accessed 4 April 2019]. Source adapted.]

The image shows a transverse section through a collecting duct in a vertebrate kidney.

[Source: Professor Peter Takizawa, Yale University]

How is the movement of materials across the wall of the collecting duct affected by the release of ADH from the pituitary gland?

A. There is increased movement of water in the direction of arrow I.

B. There is increased movement of sodium in the direction of arrow I.

C. There is increased movement of water in the direction of arrow II.

D. There is increased movement of sodium in the direction of arrow II.

Suggest reasons for the high percentage of fatal cases at Ebola treatment centres.

Explain the process of muscle contraction.

The table shows the results of blood type tests on samples from four individuals. Which row represents an individual who can accept transfusions from people with blood type AB?

[Source: © International Baccalaureate Organization 2019]

Explain the production and role of antibodies in defense against bacterial pathogens in humans.

Concerns have been raised about the effect of rising pollution levels on sperm production in men. To investigate the possible effects of pollution on spermatogenesis, sperm samples from men of similar ages were collected in Kolkata in the 1980s and 2000s. The box plot represents the mean and range of sperm counts in the 1980s and 2000s.

[Source: Republished with permission of Elsevier Science and Technology Journals, from ‘Semen quality and age-specific changes: A study between two decades on 3729 male partners of couples with normal sperm count and attending an andrology laboratory for infertility-related problems in an Indian city’, Dyutiman Mukhopadhyay, Alex C. Varghese, Manisha Pal, Sudip K. Banerjee, Asok K. Bhattacharyya, Rakesh K. Sharma, and Ashok Agarwal, Fertility and Sterility, 93 (7), 2009; permission conveyed through Copyright Clearance Center, Inc]

A hypothesis has been suggested that pollution may have a negative effect on spermatogenesis. Evaluate whether the data support this hypothesis.

The graph shows changes in the concentration of an antibody in the blood of an individual subjected to two separate infections at time X and time Y.

ADH (antidiuretic hormone) is a peptide hormone that is produced in the hypothalamus. Explain its action in the human body.

Explain the production of antibodies in humans.

What structure is indicated by the arrows?

[Source: Courtesy Roger Craig, University of Massachusetts]

A. One muscle fibre

B. One sarcomere

C. One myofibril

D. One Z line

The diagram shows two states of skeletal muscle, relaxed and contracted.

[Source: Provophys/Wikipedia. File licensed under CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0/)]

Which process is part of muscle contraction?

A. Myosin filaments cause the actin filaments to shorten.

B. Ca²⁺ from the sarcoplasmic reticulum binds to the myosin heads.

C. ATP provides energy for the movement of the myosin heads.

D. Ca²⁺ binds to tropomyosin and uncovers troponin.