Practice Paper 1A (SL IB Biology)

Water (H₂O) is a polar molecule, whereas methane (CH₄) is nonpolar. Which of the properties of methane is explained by methane's lack of polarity?

A short piece of DNA 19 base pairs long was analysed to find the number of nucleotide bases in each of the polynucleotide strands. Some of the results are shown below.

How many nucleotides containing adenine (A) were present in strand 2?

Which of the following would be the result of analysing a DNA molecule 14 000 base pairs in length?

The diagram shows a bacterium.

Which three structures are found in both an animal cell and this bacterial cell?

Which of the following chemical groups does not bond directly with the central carbon of an amino acid?

The Davson-Danielli model of cell membrane structure stated that cell membranes consisted of a phospholipid bilayer sandwiched between two layers of protein.

Which piece of evidence would have contributed to the falsification of the Davson-Danielli model and the acceptance of the fluid mosaic model?

During a gas exchange investigation, measurements were recorded from four animals that were observed as they breathed normally over a period of 5 minutes. Note that the efficiency of gas exchange was the same in all four animals and that tidal volume refers to the volume of air that moves into the lungs with each normal breath.

Which animal had the highest oxygen intake during five minutes of normal breathing?

Erythrocytes (red blood cells) have a diameter of 7 000 nm. Pancreatic cells have a diameter of 35 µm.

Which of these statements about the relative sizes of these cells is correct?

A student drew a diagrammatic representation of a transverse section of a plant stem based on what they saw using a light microscope.

Identify the correct labels required for the drawing above.

Which option correctly lists some abiotic features of an ecosystem?

The following statements apply to enzyme-catalysed reactions. Which row of the table best describes the sequence of events in an anabolic reaction?

Scientists extracted enzymes from different parts of the digestive tract of a mammal. The containers of enzyme samples got mixed up with each other before the scientists could label them. In order to identify the enzymes, they monitored the enzyme activity of each sample at different pH levels to determine the optimum pH for each.

The graph below shows the results for two of the samples (X and Y).

Which of the following would be the most valid conclusion that the scientists can draw from these results?

Some students were investigating the production of carbon dioxide from anaerobic respiration in yeast at different temperatures. They had access to the apparatus to carry out two different methods.

Method 1: Using a gas syringe, students collected gas produced by yeast at different temperatures.

Method 2: Using limewater and a delivery tube, students counted the number of bubbles of gas produced by the yeast at different temperatures, and used limewater to show that it was carbon dioxide.

Which method should the students use and why?

Paper chromatography can be used to separate photosynthetic pigments obtained from chloroplasts. The chromatography strip shows distinct coloured pigment bands. Which pigments are represented by bands 3 and 4?

The graph shows the absorption spectra for chlorophyll a.

Which of the following statements, relating to the absorption spectra for chlorophyll and the action spectrum of photosynthesis for green plants, are correct?

I. The absorption spectra of chlorophyll pigments are obtained by measuring their absorption of indigo, violet, blue, green, yellow, orange and red light, whereas the action spectrum of chlorophyll is the wavelengths of light that bring about photosynthesis.

II. The absorption spectra for chlorophyll and the action spectrum of photosynthesis are both plotted using % absorbance on the Y-axis.

III. The absorption spectra for chlorophyll and the action spectrum of photosynthesis both display two main peaks, including a larger peak in the red region (~450 nm) and a smaller peak in the blue region (~670 nm).

IV. The absorption spectrum of chlorophyll displays a trough in the green/yellow portion of the visible spectra (~550 nm), whereas the action spectrum of photosynthesis does not.

A person is admitted to hospital after suffering a stroke. It was found that the suprachiasmatic nucleus in the hypothalamus of the brain was damaged by the event. This resulted in the pineal gland secreting less melatonin into the bloodstream.

Which of the following changes would be observed in the patient?

An antibiotic sensitivity test was performed on bacteria isolated from a patient’s throat.

The diagram shows the results of the four antibiotics tested.

Which one should be used to treat the disease?

Lefamulin™ is a newly-developed antibiotic that binds to the 50S bacterial ribosomal subunit.

It was approved by the US Food and Drug Administration (FDA) in August 2019 for the treatment of pneumonia.

Which is the mode of action of Lefamulin™?

In a woodland habitat, blue tits and other small birds feed on various species of caterpillar and beetle, which themselves feed on the leaves of trees and herbaceous plants. 

Which of the following statements accurately describes a population within this example?

The diagram shows the outcomes from four different models of DNA replication after one nuclear division. The parent DNA is shown in black and the newly synthesised DNA is shown in grey.

Which diagram represents semi-conservative DNA replication?

What is the correct order of events for the stages of PCR shown in the diagram?

The diagram below represents an electron micrograph of eukaryotic polysomes.

What is the main advantage that polysomes give to a eukaryotic cell?

A short section of mRNA that was produced after transcription occurred has the following base sequence:

AAACUUCUCAUAGAACGG

The following table shows the base sequence for codons and the corresponding amino acids that they code for.

Which of the following would represent the correct amino acid sequence coded for by this section of mRNA?

The diagram shows a pair of homologous chromosomes at the beginning of prophase I of meiosis, and four possible examples of crossing over, A - D

Which of the four representations of crossing over cannot occur in meiosis I?

Identify the set of images that correctly shows follicle development during the course of the menstrual cycle.

In which of the following scenarios would there be an increase in the breakdown of glycogen in the liver?

Research was carried out on beak size in the island-living finch species Geospiza fortis. G. fortis feeds on seeds, which are plentiful, small, and soft in the years when the weather is normal, but which become larger and tougher in drought years. Some of the research results are shown in the graph below.

Which of the following statements explains the results in the graph?

Which of the following considerations should be taken into account when building a mesocosm to test the impact of a particular environmental variable?

Different greenhouse gases have different global warming potential, or GWP.

 Which factors contribute to the global warming potential of greenhouse gases?