The bacterium Neisseria gonorrhoeae causes infections related to the human reproductive system. The graph shows the percentage of samples in which this bacterium showed resistance to six antibiotics over a period of ten years.

What is a possible explanation for the total percentage resistance being larger than 100% in 2010?

A. People do not take the antibiotics as prescribed.

B. More people have been sampled in that year.

C. There was an epidemic of Neisseria gonorrhoeae in that year.

D. Some bacteria are resistant to more than one antibiotic.

D

Cladograms can be created by comparing DNA or protein sequences. The cladogram on the left is based on DNA sequences and the cladogram on the right is based on comparing protein sequences.

What is the reason that cladograms based on DNA sequences are more reliable predictors of the phylogenetic relationship of species than cladograms based on protein sequences?

A. Amino acids are not as chemically stable as DNA nucleotides.

B. DNA mutates but amino acids do not.

C. Several different triplets of bases can code for the same amino acid.

D. There are 20 different amino acids but only 4 nucleotides.

C

What process best explains the formation of different pentadactyl limbs?

A. Adaptive radiation

B. Interbreeding

C. Selective breeding

D. Convergence

A

Below is a phylogenetic tree of the three domains.

There are important differences between the three domains. Which of these domains have organelles?

A. Eubacteria and archaea

B. Archaea only

C. Eukaryotes and archaea

D. Eukaryotes only

D

What is a direct consequence of the overproduction of offspring?

A. Individuals become more adapted to the environment.

B. They will be subject to intraspecific competition.

C. They will diverge to produce different species.

D. They will suffer mutations.

B

The images show a structure found on members of a phylum of green plants.

[Source: left: Pratheep P S, www.pratheep.com (CC BY-SA 3.0) https://creativecommons.org  right: Curtis Clark (CC BY-SA 3.0) https://creativecommons.org/licenses/by-sa/3.0/.]

What is the name of the phylum to which the organisms belong?

A. Coniferophyta

B. Angiospermophyta

C. Filicinophyta

D. Bryophyta

A

The diagram represents a cladogram of the family Procyonidae.

What would justify classifying these organisms into four different genera?

A. They live in different habitats.

B. They do not share any common ancestors.

C. There are enough differences between them.

D. The number of times that the species have split.

C

What is the major contributor to the increase in antibiotic resistance in bacteria?

A. Sexual reproduction
B. Mutation
C. Natural selection
D. New antibiotics

C

The graph shows the proportion of a bacterial population of Neisseria gonorrhoeae, displaying resistance to the antibiotic tetracycline.

[Source: © All rights reserved. Canadian Antimicrobial Resistance Surveillance System Report, 2016. Public Health Agency of Canada. Adapted and reproduced with permission from the Minister of Health, 2022.]

What can be deduced from this graph?

A. Bacteria with beneficial adaptations survive and pass on their genes.

B. Immunity to tetracycline is triggered by over-use of the antibiotic.

C. Genetic variation in this bacterial population is increasing.

D. Use of tetracycline inhibits the growth of antibiotic-resistant N. gonorrhoeae.

A

This question attracted the most criticism from teachers on G2 forms. The graph showed fluctuating levels of antibiotic resistance, with an overall trend of increasing resistance. Candidates were expected to understand that antibiotic resistance is a heritable trait, so a change in antibiotic resistance levels is evolution. The explanation of increasing resistance levels is therefore based in natural selection: bacteria with genes for resistance have an advantage so survive, reproduce and pass on their genes. After careful scrutiny of the question, it was decided that there was a second acceptable answer. Although the graph does not provide information on antibiotic use, it was not unreasonable to deduce that using the antibiotic causes evolution by acting as a selective agent. Both answers A and D were therefore marked as correct in order to award the benefit of the doubt. The question has been altered for the published version for the examinations CD, with A being the correct option.

What would restrict evolution by natural selection, if a species only reproduced by cloning?

A. Too few offspring would be produced.

B. Mutations could not occur.

C. The offspring would show a lack of variation.

D. The offspring would be the same sex as the parent.

C

This was another example of a question where a high percentage of candidates answered correctly and the discrimination index was therefore low. In this case there was widespread understanding of the consequences of cloning for the rate of evolution by natural selection.

Which is a characteristic of both bryophyta and filicinophyta?

A. Vascular tissue

B. Membranous leaves

C. Release of spores

D. Evergreen spines

C

Mammals, birds and reptiles have an embryonic tail that may disappear during development.

What is the most likely explanation?

A. Mammals have lost their tail by evolution.

B. All vertebrates have a common ancestor.

C. Mammals, birds and reptiles are identical when they are embryos.

D. Some physical similarities of vertebrates are analogous.

B

The expected explanation of the presence of tails in vertebrate embryos and subsequent disappearance during development in some species was that vertebrates have a common ancestor which had a tail. All the other possible answers were incorrect — not all mammals are tailless, vertebrate embryos are not all identical, and physical similarities in vertebrates are more likely to be homologous than analogous. Nearly half of candidates answered the question correctly and the discrimination index for this question was relatively high.

What causes variation within a population?

A. Fertilization and change in the environment

B. Fertilization and mutation

C. Mutation and evolution

D. Evolution and adaptive radiation

B

If seeds of an unknown species of plant are discovered, what assumption can be made about the species?

A. Its male gametes are contained within pollen.

B. Its seeds are contained within fruits.

C. It is in the domain archaea.

D. It is in the phylum angiospermophyta.

A

Candidates showed poor knowledge on conifers, as many assumed that only angiosperms produce seeds. This topic is found in 5.3 of the guide.

Which organism is a member of the filicinophyta? (Note that these are not to scale)

[Source: A: Sanjay ach/https://creativecommons.org/licenses/by-sa/3.0/deed.en
B: Vaelta/https://creativecommons.org/licenses/by-sa/3.0/deed.en
C: Andrey Zharkikh/https://creativecommons.org/licenses/by/2.0/deed.en
D: courtesy of Caroline Needham]

A

Which pentadactyl limb is adapted for flight?

[Source: adapted from Volkov Vladislav Petrovich, https://en.wikipedia.org/wiki/Homology_(biology)#/media/File:Homology_
vertebrates-en.svg and Zebra.element, https://en.wikipedia.org/wiki/File:Bat_mouse_forelimbs.png]

D

Lichens are returning to the forests of the industrial areas of the United Kingdom due to strict pollution control.

What is the expected outcome in the population of peppered moths (Biston betularia)?

A. Increased numbers of light-coloured peppered moths
B. Increased industrial melanism in peppered moths
C. Increased predation of peppered moths
D. Increased speciation of peppered moths

A

What information can be deduced from the sequence of nodes in a cladogram?

A. The geological period in which the species in the clade diverged from their common ancestor

B. The probable sequence of divergence among the species in the clade

C. The number of characteristics the species have in common

D. The number of mutations that have occurred since the species shared a common ancestor

B

Which phyla have bilateral symmetry?

A. annelida, arthropoda, platyhelmintha

B. porifera, arthropoda, platyhelmintha

C. cnidaria, porifera, mollusca

D. porifera, annelida, mollusca 

A

The cladogram was constructed using DNA base sequences from six species. Which node indicates the greatest difference in base sequences?

[Source: © International Baccalaureate Organization 2018]

A

Which is the hierarchy of taxa in order of decreasing numbers of species?

A. domain, phylum, order, family

B. phylum, order, family, class

C. domain, phylum, order, class

D. phylum, class, family, order

A

What is required for natural selection to occur?

I. Acquired characteristics

II. Advantageous characteristics

III. Genetic variation

A. I only

B. I and III only

C. II and III only

D. I, II and III

C

The answers to this question show poor knowledge of the requirements for natural selection, as many candidates believed acquired characteristics are needed.

Scientists studying ground finches (Geospiza fortis) on the island of Daphne Major in Galapagos found great differences in the shapes of the beaks.

[Source: Public domain.]

What is the explanation for this variation in beak shape between the birds?

A. Ground finches grow larger beaks if there is competition for food.

B. They belong to different species.

C. They are adapted for different diets.

D. The more a beak is used by a ground finch, the larger it becomes.

C

A plant has cambium in its vascular tissue and pollen is produced in male cones. The plant disperses seeds but does not produce fruit. In which phylum does this plant belong?

A. Coniferophyta

B. Angiospermophyta

C. Filicinophyta

D. Bryophyta

A

Which is an example of speciation?

A. Selective breeding to produce new varieties of the wheat Triticum aestivum with higher crop yield

B. Evolution of different courtship behaviours in separate populations of the cricket Gryllus rubens

C. Natural selection leading to an increase in the frequency of darker individuals of Biston betularia

D. Selective feeding by koalas (Phascolarctos cinereus) on Eucalyptus species

B

Some G2 forms pointed out that speciation is not part of the SL material and only occurs in HL. Although there may be some justification in the comments, it was assumed that candidates would deduce what was required from their study of Topic 5.1 (Evidence for evolution) — populations of a species can gradually diverge into separate species by evolution. The question performed well according to difficulty and discrimination statistics.

The DNA base sequences in a gene coding for a particular protein in four different species are shown. Locations where mutations have occurred resulting in changes to the base sequences are outlined in boxes.

[Source: © International Baccalaureate Organization 2019]

Which cladogram shows the most likely phylogenetic relationship between the four species, based on the data provided?

D

The chart shows features of three organisms X, Y and Z.

To which domain does each organism belong?

B

The images show a guinea pig, a mouse, a horse and a whale.

Which features support the classification of these four species in the same class?

A.  All are warm-blooded and breathe air.

B.  All have evolved from primates.

C.  All have hair or fur and feed their young with milk.

D.  All have a notochord, vertebrae and give birth to live young.

C

Which phylum shows radial symmetry?

A. Annelida

B. Cnidaria

C. Platyhelmintha

D. Porifera

B

Which invertebrate phylum is characterized by a segmented body and bilateral symmetry?

A. Arthropoda

B. Mollusca

C. Porifera

D. Cnidaria

A

A dichotomous key can be used to distinguish four types of plant. Which of the plants could be a bryophyte?

A

This was the third most difficult question on the paper in terms of the percentage of candidates answering it correctly. To find the correct answer the only required knowledge was that bryophytes do not have vascular tissue.

The scientific name of the Wakatobi flowerpecker is Dicaeum kuehni.

Which species is most closely related?

A. Amerila kuehni
B. Wakatobi white-eye
C. Kuehneon duchyense
D. Dicaeum celebicum

D

Which evolutionary pathway is most likely to result in the evolution of analogous structures in Species W and Z?

C

This question performed well in terms both in terms of difficulty and having the highest discrimination on the paper.

The cladogram shows one theory of how species of hominin evolved.

What can be deduced using the information in the cladogram?

A. The closest species to K. platyops is A. africanus.

B. A. afarensis is extinct.

C. The DNA of H. sapiens is the same as that of H. ergaster.

D. H. sapiens and P. robustus shared a common ancestor.

D

Which evidence for evolution do the common features in the bone structure of vertebrate limbs provide?

A. Adaptive radiation
B. Divergent radiation
C. Convergent evolution
D. Discontinuous variation

A

Which is an example of natural selection?

A. A giraffe stretching its neck to reach higher leaves

B. A juvenile bird learning to sing

C. Development of antibiotic resistance in bacteria

D. Selective breeding of tail-less cats

C

The diagrams show various wings.

[Source: for pterodactyl, bird and bat wings:
John W. Merck, University of Maryland, College Park, Department of Geology;
for insect wing: Halvard Hatlen https://upload.wikimedia.org/wikipedia/commons/0/0f/Dip-trichoceridae-wing.png]

Which statement describes the relationship between the structures of the wings?

A. The bat wing and the insect wing are homologous because they have the same function.

B. The limbs of the bird and bat wings are homologous due to convergent evolution.

C. The wings of the pterodactyl and the bat are analogous due to divergent evolution.

D. The bones of the wings of the pterodactyl, bird and bat are homologous as they have a common ancestor.

D

Data regarding the presence (+) or absence (–) of five traits in several different species are shown in the table.

Which cladogram best represents the relationship between the five species?

A

Which of the organisms A–D, identified by the key, represents a reptile?

B

A bacterial population with no resistance to an antibiotic may develop into a bacterial population with some resistance to an antibiotic. Which event could lead to this?

A. Antibiotic resistance was inherited from an ancestral population.

B. An antibiotic resistance plasmid is received from a bacterium in another population.

C. The enzyme needed for antibiotic resistance is received from a bacterium in another population.

D. The bacterial population mutated in response to antibiotics in the environment.

B

On the islands of the St Kilda chain, off the coast of Scotland, there are small birds called St Kilda wrens (Troglodytes troglodytes hirtensis). They look similar to wrens on the mainland of Scotland (Troglodytes troglodytes indigenus), but they are larger and there are differences in the colour of their feathers.

What is the most likely explanation for these differences?

A. Convergent evolution

B. Stabilizing natural selection

C. Gradual divergence

D. Exposure to similar selection pressure

C

What reduces variation in a population?

A. Meiosis

B. Mutation

C. Natural selection

D. Sexual reproduction

C

The cladogram shows some of the groups in the three domains.

[Source: Adapted from Eric Gaba (Sting, fr:Sting), Cherkash, Public domain, via Wikimedia Commons.
https://commons.wikimedia.org/wiki/File:Phylogenetic_tree.svg.]

What domains do X, Y and Z represent?

C

The diagram shows features of three plant phyla.

Which phyla are represented by R, S and T?

D

Balkan green lizards, Lacerta trilineata, living in mainland Greece eat mostly insects but also small amounts of plants. The same species living on Greek islands (where insects are scarce) show a greater percentage of those physical traits useful for eating plants than the mainland lizards.

[Source: Penny Turner/Wikimedia file licensed under CC BY-SA 4.0
https://creativecommons.org/licenses/by-sa/4.0/deed.en]

What is the biological explanation for these observations?

A. Variation in each lizard population allowed adaptation to occur.

B. Lizards migrated to areas where they were better adapted.

C. Lizards on the islands diverged due to lack of interbreeding with the mainland population.

D. Homologous structures have prevented separate species from evolving.

C

Humans have been improving crop species for thousands of years by cross-breeding plants with desirable characteristics. The photograph shows the changes in dry cobs of corn (Zea mays) over 10 000 years.

[Source: Evolution of Maize Cobs © Robert S. Peabody Institute of Archaeology,
Phillips Academy, Andover, Massachusetts. All Rights Reserved.]

What is the name of the process that was used to produce modern corn?

A. Selective breeding

B. Adaptive radiation

C. Discontinuous variation

D. Natural selection

A

In which domain are bryophyta found?

A. Plantae
B. Archaea
C. Eubacteria
D. Eukaryote

D

The table shows the number of differences between humans and other selected organisms for the protein cytochrome c oxidase. This protein, consisting of 104 amino acids, is located in the mitochondria and functions as an enzyme during cell respiration.

If the data were used to draw a cladogram, which chordates would be furthest apart from humans?

A. Chimpanzee because it has zero differences

B. Fruit fly because it has the most differences

C. Tuna fish because it is the chordate with the most differences

D. Horse because it is in the same class

C

Which are examples of homologous structures?

A. The wings of bats and butterflies

B. The fins of fish and whales

C. The hindlimbs of frogs and grasshoppers

D. The forelimbs of primates and penguins

D

The image shows an organism belonging to the Kingdom Animalia.

[Source: Titan beetle male. Locality: “RK4,5 route Cacao”, French Guiana
© 2011, Didier Descouens https://creativecommons.org/licenses/by-sa/4.0/]

What feature does this organism have in common with all members of the phylum chordata?

A. Legs and wings

B. Mouth but no anus

C. Bilateral symmetry

D. Chitinous exoskeleton

C

Which factor(s) would favour evolution by natural selection?

I. Long lifespans

II. Favourable characteristics acquired by individuals during their lifetime

III. Variation within a species

A. II only

B. III only

C. I and II

D. I and III

B

The question did discriminate well. It was commented that the word ‘lifespans’ may be difficult for non-native English speakers.

The plant in the diagram has vascular tissue and reproduces by spores.

[Source: Auer, A., 2007. Nature print, Alois Auer. [image online] Available at: https://commons.wikimedia.org/wiki/File:Nature_print,_Alois_Auer.jpg [Accessed 10 October 2019].]

To which phylum does the plant belong?

A. Bryophyta

B. Filicinophyta

C. Coniferophyta

D. Angiospermophyta

B

An animal has the following characteristics: bilateral symmetry, mouth but no anus, ribbon shape. Which phylum does the animal belong to?

A. Mollusca

B. Cnidaria

C. Annelida

D. Platyhelmintha

D

Which encircled area shows a clade?

A

Which of these structures is not homologous?

[Source: https://en.wikipedia.org/wiki/Comparative_anatomy#/media/File:Homology_vertebrates-en.svg and
https://commons.wikimedia.org/wiki/File:Insect_leg_scheme.svg]

C

What is the reason for antibiotics not damaging human cells?

A. The dose is too small to be harmful.

B. The dose is taken for only a short time.

C. Antibiotics occur naturally in humans.

D. Human metabolism is different from bacterial metabolism.

D

Which process results in decreased variation?

A. Meiosis

B. Mutation

C. Sexual reproduction

D. Natural selection

D

There was some concern among teachers that this question might be misinterpreted, but three quarters of candidates answered correctly and the discrimination index was high. Natural selection can decrease variation by eliminating alleles that reduce fitness.

The pentadactyl limbs of mammals, birds, reptiles and amphibians are examples of which kind of structures?

A. Homologous

B. Analogous

C. Vestigial

D. Convergent

A

A locust is an arthropod. For invertebrate groups, which recognition feature is found only in arthropods?

A. Bilateral symmetry

B. Jointed appendages

C. Wings

D. Segmented body

B

Only about a third of candidates answered this question correctly and the discrimination index was relatively low. For entirely understandable reasons, candidates' understanding of arthropod classification and the use of recognition features was rather poor. A recognition feature should be possessed by all the members of a group and ideally by no members of other groups. Bilateral symmetry and a segmented body could be rejected because some non-arthropods have them. Wings could be rejected, because among arthropods, only insects have them. The remaining answer, jointed appendages was correct.

The image shows the northern sea nettle (Chrysaora melanaster).

[Source: Aflo, 2015. Northern sea nettle (Chrysaora Melanaster) floating, with Mackerel fry (Carangidae) Izu, Japan. [image
online] Available at: https://www.naturepl.com/search/preview/northern-sea-nettle-chrysaora-melanaster-floating-withmackerel-
fry-/0_01489405.html [Accessed 23 March 2020].]

To which phylum does C. melanaster belong?

A. Porifera

B. Cnidaria

C. Platyhelmintha

D. Annelida

B

An organism has the following characteristics:

• single opening for ingestion and egestion
• radial symmetry
• tentacles with stinging cells.

In what phylum would it most likely be classified?

A. Annelida

B. Cnidaria

C. Platyhelminthes

D. Porifera

B

The cladogram shows the relationships of five species I to V.

Which species is/are most closely related to IV?

A.  V only

B.  II and III

C.  III and V

D.  II, III and V

B

The figwort family is a large one consisting of many flowering plants that look similar. For what reason have some members of the family been reclassified into a new family?

A. Cladistic analysis shows the differences in flower structure to be fewer than the shared similarities.

B. DNA analysis shows the similarities in flower shape to be a product of convergent evolution.

C. DNA analysis shows some of the families to have suffered recent mutations in only one gene.

D. DNA analysis shows the similarities between the seed dispersal strategies to be a product of divergent evolution.

B