SL Paper 2
Organisms have evolved a great diversity of cell types.
Describe the endosymbiotic theory.
Explain the need for halving the chromosome number during a sexual life cycle and how this is done.
Outline the binomial system of classification.
Describe briefly the endosymbiotic theory.
Outline how photosynthesis produces glucose.
Discuss the control of blood glucose levels and the consequences if they are not maintained.
Pictured below are Louis Pasteur’s original drawings of swan-necked flasks.
Describe how Pasteur’s experiments provided convincing evidence to falsify the concept of spontaneous generation.
State the function of life in Paramecium that is carried out by:
cilia.
State the function of life in Paramecium that is carried out by:
the contractile vacuole.
Discuss the advantages and disadvantages of the use of adult stem cells.
Explain the role of decomposers in an ecosystem.
The diagram shows the stages in the cell cycle.
State processes occurring during interphase.
Using the letter C, label the stage on the diagram where chromosome supercoiling occurs.
Using the letter M, label the stage on the diagram where sister chromatids migrate to opposite poles.
Distinguish between the outcomes of a cell dividing either by mitosis or meiosis.
The mitotic index is an important prognostic tool for predicting the response of cancer cells to chemotherapy. Outline how the mitotic index is calculated.
The diagram shows part of two neurons.
[Source: © International Baccalaureate Organization 2020.]
Outline how the amphipathic properties of phospholipids play a role in membrane structure.
State the name of the structure shown.
X indicates the movement of a structure in the neuron. Explain what events trigger this movement and what happens next.
An oval-shaped stem cell cluster is shown in the micrograph.
[Source: Sontag, S., Förster, M., Seré, K. and Zenke, M., 2017. [online] Available at: https://bio-protocol.org/e2419 [Accessed
6 December 2019]. Source adapted.]
State the main characteristic of stem cells.
Calculate the maximum diameter of the stem cell cluster on the micrograph, showing your working and giving the units.
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State one therapeutic role of stem cells.
Discuss how the use of stem cells to treat hereditary diseases could affect the person who received the treatment and their progeny.
Outline the stages in the production of mRNA by transcription.
Describe the functions of proteins in cell membranes.
Explain how natural selection can lead to speciation.
Outline four types of membrane transport, including their use of energy.
Draw the structure of a dipeptide.
Explain the action of enzymes in digestion and the different roles of at least two named enzymes that are produced in the pancreas.
The structure of prokaryotic cells has been investigated using electron microscopy. Draw a labelled diagram to show prokaryotic cell structure.
Outline the reasons for differences between the proteomes of cells within a multicellular organism.
Discuss the cell theory and its limitations.
Substances can move into and out of cells through the cell membrane.
Outline the significance of surface area to volume ratio in the limitation of cell size.
Describe transport across cell membranes by osmosis.
Explain the adaptations of the small intestine to its function.
Draw a labelled diagram to show the fluid mosaic model of the plasma membrane.
Unicellular and multicellular organisms share the same functions of life. Outline four functions of life.
The structure of organisms is based on organic molecules containing carbon. Explain the cycling of carbon in an ecosystem.
The image is an electron micrograph.
Determine, with a reason, whether the image is of a prokaryotic cell or eukaryotic cell.
(i) State the process that divides one nucleus into two genetically identical nuclei.
(ii) Explain how the cell cycle is controlled.
Reproduction in eukaryotes can be sexual or asexual.
Describe the origin of eukaryotic cells according to the endosymbiotic theory.
Explain how hormones are used to control the human menstrual cycle.
Outline natural methods of cloning in some eukaryotes.
The photomicrograph below shows the protozoan Paramecium caudatum.
[Source: Deuterostome, CC BY-SA 3.0
https://creativecommons.org/licenses/by-sa/3.0, via Wikimedia Commons.]
State the genus of this organism.
State the domain in which it is classified.
Outline the method of nutrition carried out by P. caudatum.
Outline one aspect of how P. caudatum carries out homeostasis.
Apart from the ribosomes, explain the evidence for the endosymbiotic theory of the origin of eukaryotic cells.
Native oyster populations are decreasing where rivers meet the ocean along the northwest coast of North America. These oyster populations are being attacked by a gastropod.
It is known that oysters and gastropods have hard parts composed of calcium carbonate and that ocean acidification is increasing. Studies were carried out using juvenile oysters and gastropods to investigate the effects of acidification on the decrease in the population of oysters.
The first step was to raise oysters in two different mesocosms. One had seawater at a normal concentration of CO2 and the other had sea water with a high concentration of CO2. Gastropods were raised in two further mesocosms with normal and high CO2 concentrations respectively.
A juvenile gastropod will attack a juvenile oyster by using its tongue-like structure (radula) to drill a hole through the oyster shell. Once the hole has been drilled, the gastropod sucks out the soft flesh. Researchers investigated the shell thickness at the site of the drill hole in relation to the size of the oyster. The results are seen in this graph.
Equal numbers of oysters raised in seawater with a normal CO2 concentration and in seawater with a high CO2 concentration were then presented together to the gastropod predators in seawater with a normal CO2 concentration. The same numbers of oysters from the two groups were also presented together to the gastropods in seawater with a high CO2 concentration. The bar charts show how many of the oysters were drilled by the gastropods and the mean size of drilled oysters.
Outline how acidified sea water could affect the shells of the oyster.
Outline the trends shown in the data in the graph.
Estimate how much smaller drilled oysters raised in seawater at a high CO2 concentration were than drilled oysters raised in seawater at a normal CO2 concentration.
Deduce from the data in the bar charts which factors were and were not correlated significantly with the number of oysters drilled by the gastropods.
Suggest reasons for the differences in the numbers of oysters drilled, as shown in the bar charts.
The radula in a gastropod is hard but not made of calcium carbonate. Outline how this statement is supported by the drilling success of the gastropods in seawater with normal or high CO2 concentrations.
Using all the data, evaluate how CO2 concentrations affect the development of oysters and their predation by gastropods.
Identify the stage of mitosis labelled X in the image, giving a reason.
[Source: Copyright 2002, The Trustees of Indiana University]
Outline the use of a karyogram during pregnancy.
The electron micrograph shows the structures in an exocrine gland cell of the pancreas.
Glands are organs that secrete and release particular chemical substances. Melatonin is an important hormone secreted in the pineal gland in the brain. Describe its role in mammals.
State the principal product of this cell.
Using the table, identify the organelles labelled I and II on the electron micrograph with their principal role.
The Davson-Danielli model of membrane structure was proposed in the 1930s. When electron micrographs of membranes were first produced, they were used as evidence for this model. The micrograph shows two adjacent membranes (indicated with arrows).
[Source: DENNIS KUNKEL MICROSCOPY/SCIENCE PHOTO LIBRARY.]
Explain how the appearance of membranes in electron micrographs was used as evidence to support the Davson-Danielli model.
Outline the use of human embryonic stem cells (hESC) to treat Stargardt’s disease.
The most common form of Stargardt’s disease is known to be autosomal recessive. Using a Punnett grid, deduce the probability of a child inheriting Stargardt’s disease, if both of the parents are carriers of the disease but do not have the disease themselves.
Outline the cell theory.
State two functions of life.
List three characteristics of eukaryotic homologous chromosomes.
Using the following table, compare and contrast anaerobic cell respiration in yeasts and in humans. The first row has been completed as an example.
Every cell is surrounded by a cell surface membrane which regulates the movement of materials into and out of the cell.
Draw an annotated diagram of the fluid mosaic model of membrane structure.
Describe the processes involved in absorbing different nutrients across the cell membrane of villus epithelium cells lining the small intestine.
Explain the events that occur during a nerve impulse and how the impulse is propagated along an axon.
Identify which electron micrograph shows a mitochondrion, providing one observation to support your choice.
Discuss the evidence for the theory that mitochondria may have evolved from free-living prokaryotes by endosymbiosis.
Draw a section of the Singer-Nicolson model of an animal cell membrane.
Outline the principles used by scientists to classify organisms.
Explain the movement of energy and inorganic nutrients in an ecosystem.
Outline reasons for the therapeutic use of stem cells.
Describe how leaf cells make use of light energy.
Explain how cells and cell components in the blood defend the body against infectious disease.
Label the area where cellulose is found in the micrograph of a plant cell.
[Source: BIOPHOTO ASSOCIATES/Getty Images]
Cellulose is the most abundant organic polymer on Earth. Describe the structure of cellulose.
Outline one reason for humans being unable to digest cellulose.
Explain the advantages of having both lipid and carbohydrate as energy stores in the human body.
Antiretroviral drugs are used to treat Human Immunodeficiency Virus (HIV) infections. Zidovudine (ZDV) and nevirapine (NVP) are examples of antiretroviral drugs. There are concerns that these drugs may be toxic to body cells in mitosis. In a study using Allium cepa, root tips were exposed to the drugs for 96 hours at a range of concentrations. The control treatment was a drug concentration of 0μmol. In the graph, root lengths after the 96-hour treatment period are expressed as a percentage of the length of the control.
[Source: Onwuamah CK, Ekama SO, Audu RA, Ezechi OC, Poirier MC, Odeigah PGC (2014) Exposure of Allium cepa Root Cells to Zidovudine or Nevirapine Induces Cytogenotoxic Changes. PLOS ONE 9(3): e90296. https://doi.org/10.1371/journal.pone.0090296 (CC0 1.0 - https://creativecommons.org/publicdomain/zero/1.0/).]
Both ZDV and NVP are believed to have a damaging effect on the process of mitosis but ZDV in particular is believed to block the formation of the spindle.
[Source: Medical Images / Carolina Biological.]
Mitosis plays an important role in tissue regeneration and can be an important factor in recovery from surgery. The hormone leptin has been shown to promote mitosis in certain circumstances. The bar chart shows the mitotic indices of liver tissue exposed to leptin and control tissue during 72 hours after surgery.
[Source: Adapted from Cilekar M, Uysal O, Bal C, Turel S, Yılmaz S. Leptin increases mitotic index and regeneration ratio in hepatectomized rats. Med Sci Monit Basic Res. 2013 Nov 13;19:279-84. doi: 10.12659/MSMBR.889591]
Deduce the concentration of ZDV that would cause a 50 % reduction in root growth compared to the control.
Identify the root length, as a percentage of the control, resulting from a ZDV concentration of .
Compare and contrast the effect of ZDV and NVP on the growth of Allium roots.
Based on the information, suggest with a reason which of the labelled cell types will become more common in Allium root tips treated with ZDV.
Allium root tips continue to show some growth even at high concentrations of NVP. Suggest a possible reason for the growth seen in root tips with 800μmol NVP.
Deduce the change in mitotic index after 72 hours compared to the control.
Based on the data, evaluate the evidence for leptin promoting regeneration of liver tissue.
Outline the role of leptin in appetite control.
According to the cell theory, living organisms are composed of cells.
Draw the ultrastructure of a prokaryotic cell based on electron micrographs.
Outline what occurs in cells in the first division of meiosis.
Explain the role of cells in the defence against infectious disease.
The electron micrograph shows a palisade mesophyll cell.
State the name of the structures labelled I and II.
Outline the function of the structure labelled III.
The plant from which this cell was taken is in the group angiospermophyta. State one characteristic that is unique to this group of plants.
Distinguish between autotrophic nutrition and heterotrophic nutrition.
Explain how energy and nutrients are transferred in ecosystems.
Tuberculosis (TB) is an infectious disease caused by the bacterium Mycobacterium tuberculosis.
Outline the structures in M. tuberculosis that are not present in a human cell.
Explain the production of antibodies when a patient is infected with the TB bacterium.
Describe the risk to the human population of indiscriminate use of antibiotics.
The figure shows a transmission electron micrograph of rotavirus particles. Each rotavirus is about 70 nanometres in diameter.
[Source: CDC / Dr. Erskine L. Palmer]
State a reason for using an electron microscope to view this virus rather than a light microscope.
Rotavirus causes diarrhea and vomiting. Explain why viral diseases cannot be treated using antibiotics.
State an application of plasmids in biotechnology.