IB Biology Quiz: Apply Evolution And Speciation
19 questions · exam conditions
0:00
Apply Evolution And SpeciationQuestion 1 of 19

Which of the following is a necessary condition for natural selection to result in evolutionary change in a population?

The population must have a large size to ensure genetic diversity.
All individuals in the population must have an equal chance of survival.
The environment must remain stable for many generations.
The advantageous traits must be heritable.
← Back to quizzes

IB Biology Quiz

IB Biology Quiz: Apply Evolution And Speciation

Practice Apply Evolution And Speciation in IB Biology with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.

What this quiz covers

This quiz focuses on Apply Evolution And Speciation, giving you a quick way to practice the rules, question types, and explanations that matter most for IB Biology.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

All questions

Question 1

Which of the following is a necessary condition for natural selection to result in evolutionary change in a population?

  1. The population must have a large size to ensure genetic diversity.
  2. All individuals in the population must have an equal chance of survival.
  3. The environment must remain stable for many generations.
  4. The advantageous traits must be heritable. (correct answer)
Explanation: For natural selection to lead to evolution (a change in allele frequencies over generations), the traits that confer a survival or reproductive advantage must be passed on to the next generation. This requires heritability. (A) While large population size is important to counteract genetic drift, selection can occur in small populations. (B) This is the opposite of what happens in natural selection; there is differential survival. (C) Environmental change is often the driver of natural selection; a stable environment would likely lead to stabilizing selection, not necessarily change.

Question 2

Two species of fruit flies are reproductively isolated. When males of species A are crossed with females of species B, no viable offspring are produced. When males of species B are crossed with females of species A, the resulting hybrid offspring are viable but sterile. What type of isolation is demonstrated by the sterile hybrid offspring?

  1. Hybrid inviability
  2. Hybrid breakdown
  3. Hybrid sterility (correct answer)
  4. Gametic isolation
Explanation: Hybrid sterility is a postzygotic isolating mechanism in which a hybrid offspring is produced and is viable, but is unable to reproduce. The scenario explicitly states that the hybrids are sterile. (A) Hybrid inviability refers to a zygote that fails to develop or reach sexual maturity, which is described in the first cross but not the second. (B) Hybrid breakdown occurs when F1 hybrids are fertile, but the F2 generation is sterile or has reduced fitness. (D) Gametic isolation is a prezygotic barrier where gametes cannot fuse.

Question 3

In a certain plant species, a mutation occurs that results in polyploidy (possessing more than two complete sets of chromosomes). The resulting tetraploid (4n) plant is viable and fertile but can only produce fertile offspring by mating with other tetraploids or through self-pollination. It cannot produce fertile offspring with the original diploid (2n) population. This event occurs within the geographical range of the parent population. What type of evolutionary event has occurred?

  1. Allopatric speciation due to a postzygotic barrier.
  2. Allopatric speciation due to a prezygotic barrier.
  3. Sympatric speciation due to a postzygotic barrier. (correct answer)
  4. Sympatric speciation due to a prezygotic barrier.
Explanation: This is a classic example of sympatric speciation, as it occurs without geographic isolation. The mechanism is polyploidy, which instantly creates a reproductive barrier. The barrier is postzygotic because a zygote can be formed between a diploid gamete (n) and a tetraploid gamete (2n), but the resulting triploid (3n) offspring is typically sterile. Therefore, speciation is sympatric and the primary barrier described is postzygotic. (A) and (B) are incorrect because the process is sympatric. (D) is incorrect because while prezygotic barriers might evolve later, the initial, immediate barrier caused by mismatched chromosome numbers leading to sterile offspring is postzygotic.

Question 4

The forelimb of a bat and the flipper of a whale have a similar underlying bone structure, inherited from a common mammalian ancestor, but they are adapted for different functions. The wing of a bat and the wing of an insect have different underlying structures but are both adapted for flight. What terms correctly describe these two comparisons?

  1. Bat forelimb and whale flipper are analogous; bat wing and insect wing are homologous.
  2. Bat forelimb and whale flipper are homologous; bat wing and insect wing are analogous. (correct answer)
  3. Both comparisons demonstrate homologous structures resulting from adaptive radiation.
  4. Both comparisons demonstrate analogous structures resulting from convergent evolution.
Explanation: Homologous structures (bat forelimb and whale flipper) are those derived from a common ancestor but potentially modified for different functions. Analogous structures (bat wing and insect wing) are those that serve a similar function but have evolved independently in different lineages without a recent common ancestor having that trait. (A) reverses these definitions. (C) and (D) incorrectly classify both pairs of structures under the same term.

Question 5

A powerful earthquake forms a new, deep canyon that divides a population of flightless beetles. Over thousands of years, the two separated populations evolve independently and can no longer interbreed even if brought back together. What is the correct sequence of events leading to this outcome?

  1. Sympatric speciation → genetic drift → reproductive isolation.
  2. Geographic isolation → divergent evolution → reproductive isolation. (correct answer)
  3. Adaptive radiation → disruptive selection → geographic isolation.
  4. Reproductive isolation → natural selection → geographic isolation.
Explanation: This describes allopatric speciation. The first step is the physical separation of the populations by a geographic barrier (the canyon). Following this geographic isolation, the separated populations undergo divergent evolution due to different selection pressures, mutation, and genetic drift. The final outcome, which defines them as separate species, is the evolution of reproductive isolation mechanisms. (A) is incorrect because the process is allopatric, not sympatric. (C) incorrectly sequences events; geographic isolation is the cause, not the result. (D) also has the sequence wrong; reproductive isolation is the final outcome of the speciation process, not the starting point.

Question 6

Two species of crickets live in the same meadow. The males of one species produce a courtship song at a frequency of 5 kHz, while the males of the other species sing at 3 kHz. Females of each species are only attracted to the song of males of their own species. This is an example of which type of reproductive isolating mechanism?

  1. Temporal isolation
  2. Mechanical isolation
  3. Gametic isolation
  4. Behavioural isolation (correct answer)
Explanation: Behavioural isolation occurs when differences in courtship rituals or other behaviours prevent mating between species. The distinct courtship songs and female preferences are a form of this. (A) Temporal isolation involves breeding at different times. (B) Mechanical isolation involves incompatible reproductive organs. (C) Gametic isolation involves sperm and egg being unable to fuse. The barrier described in the stem happens before any mating attempt, based on behaviour.

Question 7

A population of island plants shows continuous variation in height. A severe, prolonged drought acts as a strong selection pressure, favouring plants with deep root systems and shorter stems, which reduce water loss. After several generations of drought, the average height of the plants in the population is significantly lower than before.

What type of natural selection does this scenario illustrate?

  1. Directional selection (correct answer)
  2. Stabilizing selection
  3. Disruptive selection
  4. Sexual selection
Explanation: Directional selection occurs when an extreme phenotype is favoured over other phenotypes, causing the allele frequency to shift over time in the direction of that phenotype. In this case, the drought favours shorter plants, shifting the population's average height downwards. (B) Stabilizing selection would favour the intermediate height. (C) Disruptive selection would favour both tall and short plants but not the intermediate ones. (D) Sexual selection relates to traits that increase mating success, which is not the primary pressure described.

Question 8

A single species of cichlid fish colonized a newly formed volcanic lake in Africa. Thousands of years later, the lake contains over 500 species of cichlids, each specialized for a different ecological niche (e.g., eating algae off rocks, consuming insects, preying on other fish). They are all more closely related to each other than to any cichlid species outside the lake.

This rapid diversification into numerous species to fill available niches is a prime example of:

  1. Gradualism
  2. Genetic drift
  3. Convergent evolution
  4. Adaptive radiation (correct answer)
Explanation: Adaptive radiation is the evolution of many diversely adapted species from a common ancestor upon introduction to new environmental opportunities and challenges. The scenario describes exactly this: a single ancestral species giving rise to a multitude of new species that occupy different niches within the same geographical area. (A) describes the tempo of evolution, not the pattern. (B) is a mechanism of evolution (random changes in allele frequencies) but does not describe this large-scale pattern of diversification. (C) is the evolution of similar traits in unrelated species, the opposite of what is described.

Question 9

The fact that the genetic code is nearly universal—with codons specifying the same amino acid in virtually all organisms from bacteria to humans—is considered strong evidence for evolution. Why is this so?

  1. It suggests that all life shares a single, common ancestor. (correct answer)
  2. It demonstrates that all organisms have the same number of genes.
  3. It proves that mutations occur at the same rate across all lineages.
  4. It indicates that all organisms are perfectly adapted to their environments.
Explanation: The universality of the genetic code is powerful evidence for common descent. The most parsimonious explanation for this shared, complex system is that it evolved once in a common ancestor and was inherited by all subsequent life forms. If life had multiple origins, we would expect to see multiple, different genetic codes. (A) is factually incorrect. (C) is unrelated to the genetic code itself. (D) is an incorrect conclusion; the genetic code's universality does not imply perfect adaptation.

Question 10

A large population of lizards is split into two by the formation of a river. The environment on the west side is arid and rocky, while the east side is forested and damp. After many generations, what would be the most likely initial step towards the two populations becoming distinct species?

  1. The immediate formation of postzygotic isolation mechanisms.
  2. The cessation of gene flow between the two populations. (correct answer)
  3. A sudden increase in mutation rate on only one side of the river.
  4. The development of identical adaptations on both sides of the river.
Explanation: Speciation, in this allopatric model, begins when a barrier (the river) prevents gene flow between the two subpopulations. Once gene flow ceases, the populations can diverge genetically due to different selection pressures, mutation, and genetic drift. (A) Postzygotic isolation is an outcome of divergence, not the initial step. (C) A change in mutation rate is not a necessary or likely first step. (D) The different environments would lead to divergent, not identical, adaptations.

Question 11

A species of fish in a large lake has two main food sources: small snails near the shore and plankton in the open water. Over time, the population diverges into two distinct morphs: one with a robust jaw for crushing snails and another with a fine-combed gill structure for filtering plankton. Intermediate forms are rare as they are inefficient at feeding on either source. Mating is non-random, with individuals preferring to mate with their own morph.

Which evolutionary processes are most likely occurring in this fish population?

  1. Stabilizing selection leading to allopatric speciation.
  2. Disruptive selection leading to sympatric speciation. (correct answer)
  3. Directional selection leading to temporal isolation.
  4. Convergent evolution leading to behavioural isolation.
Explanation: The scenario describes selection against the intermediate phenotype and for the two extreme phenotypes (robust jaw vs. fine gills), which is the definition of disruptive selection. Because this divergence is happening within the same lake (a single geographic area), it is a potential case of sympatric speciation, driven by ecological factors and non-random mating. (A) is incorrect as stabilizing selection would favour the intermediate form, and allopatric speciation requires a geographic barrier. (C) describes directional selection, which shifts the population mean, not splits it into two. (D) describes the evolution of similar traits in unrelated lineages, which is not what is happening here.

Question 12

Sharks (fish) and dolphins (mammals) both have streamlined body shapes and fins, which are adaptations for moving efficiently in water. However, their last common ancestor was a terrestrial reptile that did not have these features. The similarity in body shape between sharks and dolphins is a result of:

  1. Adaptive radiation from a common aquatic ancestor.
  2. Convergent evolution due to similar selection pressures. (correct answer)
  3. Homologous structures maintained through stabilizing selection.
  4. Divergent evolution leading to analogous structures.
Explanation: Convergent evolution is the process whereby distantly related organisms independently evolve similar traits to adapt to similar necessities or environments. Sharks and dolphins faced the same selection pressure (efficient movement in water) and evolved similar body plans, which are analogous structures. (A) is incorrect as their last common ancestor was not aquatic with these features, and this is not radiation. (C) is incorrect because the structures are analogous, not homologous. (D) is a contradictory statement; divergent evolution leads to homologous structures becoming different, not analogous ones.

Question 13

[HL Content] Some fossil records show long periods of morphological stasis, interrupted by short bursts of rapid evolutionary change, often coinciding with major environmental events. Other fossil records show a slow, consistent accumulation of small changes over long periods.

Which evolutionary models are described by these two patterns, respectively?

  1. Gradualism; Punctuated equilibrium.
  2. Punctuated equilibrium; Gradualism. (correct answer)
  3. Directional selection; Stabilizing selection.
  4. Allopatric speciation; Sympatric speciation.
Explanation: Punctuated equilibrium is the model that proposes long periods of little or no evolutionary change (stasis), punctuated by brief periods of rapid change. Phyletic gradualism is the model that proposes a slow, steady, and continuous rate of evolutionary change over time. The question describes these two models in that order. (A) reverses the order. (C) and (D) describe mechanisms of selection and modes of speciation, not the tempo or pattern of change seen in the fossil record.

Question 14

A population of ground-nesting birds experiences the introduction of a new, highly effective terrestrial predator. After several generations, the average height of nests from the ground has increased. Which statement most accurately explains this shift?

  1. Individual birds learned to build nests higher to protect their eggs and taught this behaviour to their offspring.
  2. The presence of the predator induced mutations for higher nest-building, which were then selected for.
  3. Birds with a pre-existing genetic predisposition to build nests higher had greater reproductive success, increasing the frequency of this trait. (correct answer)
  4. The entire population of birds collectively adapted by building higher nests to ensure the survival of the species.
Explanation: This is an example of directional selection. The correct answer (C) describes the core mechanism of natural selection: pre-existing variation within the population (some birds naturally build higher nests), a selection pressure (the new predator), and differential survival and reproduction, leading to a change in allele frequencies over time. (A) describes Lamarckian inheritance of acquired characteristics. (B) incorrectly suggests that mutations are directed by environmental needs rather than occurring randomly. (D) implies a teleological or 'group selection' perspective, which is not the standard mechanism of natural selection acting on individuals.

Question 15

The continued use of a single antibiotic to treat a bacterial infection often leads to the antibiotic becoming ineffective. From an evolutionary perspective, what is the correct explanation for this phenomenon?

  1. Individual bacteria develop immunity to the antibiotic during their lifetime and pass it to their offspring.
  2. The antibiotic causes mutations in the bacterial DNA that confer resistance.
  3. A few bacteria in the original population had a pre-existing resistance mutation, and they survived and reproduced. (correct answer)
  4. The bacteria collectively evolve resistance as a group in order to survive the presence of the antibiotic.
Explanation: Antibiotic resistance evolves through natural selection. The key is that variation (resistance mutations) already exists in the population due to random mutation. The antibiotic acts as a selection pressure, killing susceptible bacteria and allowing the pre-existing resistant ones to survive and multiply, increasing the frequency of resistance alleles in the population. (A) describes inheritance of acquired traits. (B) incorrectly implies that the antibiotic causes the specific resistance mutations, rather than just selecting for them. (D) is a teleological explanation.

Question 16

Industrial melanism in the peppered moth (Biston betularia) is a well-documented example of natural selection. In polluted industrial areas, the frequency of the dark-coloured (melanic) morph increased. What was the direct selection pressure that drove this change?

  1. The pollutants in the air directly caused mutations for dark colouration.
  2. The dark-coloured moths had a higher tolerance to the toxic pollutants.
  3. Soot from factories darkened the trees, making dark moths less visible to avian predators. (correct answer)
  4. The light-coloured moths migrated away from polluted areas, increasing the relative frequency of dark moths.
Explanation: The selection pressure was visual predation by birds. The environmental change (soot-darkened trees) altered which phenotype had better camouflage. Dark moths were better camouflaged and thus had a higher survival rate in polluted areas. (A) is incorrect as it suggests directed mutation. (B) is a plausible but incorrect hypothesis; the primary selective agent was predation, not chemical tolerance. (D) is incorrect; the change was due to differential survival within the area, not migration patterns.

Question 17

[HL Content] A population of snails exhibits a shell coiling polymorphism, where some individuals have right-coiling (dextral) shells and others have left-coiling (sinistral) shells. The direction of coiling is controlled by a single gene. Due to the mechanics of snail anatomy, dextral individuals can only successfully mate with other dextral individuals, and sinistral with sinistral. A mutation causing a switch in coiling direction in an individual's offspring could potentially lead to:

What potential evolutionary event could be triggered by a single gene mutation affecting shell coiling in snails?

  1. A rapid case of sympatric speciation due to mechanical isolation. (correct answer)
  2. Directional selection favouring the more common coiling phenotype.
  3. An example of punctuated equilibrium observed in the fossil record.
  4. Allopatric speciation driven by a founder effect from a single mutant.
Explanation: The mutation creates an instantaneous reproductive barrier within the same population (sympatric). The inability of left-coiling and right-coiling snails to mate is a form of mechanical isolation. This single gene change can therefore be the first step in the formation of a new species without any geographic separation. (B) This describes a different process; the question asks what the mutation could lead to in terms of speciation. (C) This describes a long-term pattern, not the immediate event. (D) This is not allopatric speciation because it occurs within the parent population's range.

Question 18

A scientist is studying two populations of a flowering plant. Population A lives at a high altitude and flowers in early June when its specific pollinator is active. Population B lives at a lower altitude and flowers in late July, coinciding with the activity of a different pollinator species. The two populations are not geographically isolated.

What is the primary reproductive isolating mechanism at work between these two populations?

  1. Temporal isolation (correct answer)
  2. Mechanical isolation
  3. Habitat isolation
  4. Gametic isolation
Explanation: Temporal isolation is a prezygotic barrier where two species reproduce at different times of the day, seasons, or years. In this case, the plants flower at different times (early June vs. late July), preventing gene flow between them. (A) Mechanical isolation would involve incompatible flower structures. (C) While they are in different habitats (altitudes), the primary barrier described is the timing of reproduction. (D) Gametic isolation would involve the pollen and stigma being incompatible.

Question 19

What is the role of variation in the process of natural selection?

  1. Variation is the end result of natural selection, creating new species.
  2. Variation allows populations to choose the best traits for survival.
  3. Variation provides the raw material upon which selection can act. (correct answer)
  4. Variation is reduced by natural selection to create a perfectly adapted organism.
Explanation: Natural selection acts upon the existing variation within a population. Without variation in heritable traits, there would be no differences in survival and reproduction for selection to favour, and evolution could not occur. (A) Speciation is a possible result, but variation is the starting point, not the end result. (B) This is teleological; there is no conscious choice involved in selection. (D) While some forms of selection (stabilizing) can reduce variation around a mean, variation itself is essential for selection to happen at all, and perfect adaptation is not an achievable endpoint.