Evolution of Galapagos Finches

In the Galapagos Islands, a species of finch known as Geospiza magnirostris is found primarily on the island of Santa Cruz, where its main food source is the seeds of the plant Tribulus cistoides. A volcanic eruption on a neighboring island created a land bridge to a previously isolated island, which the finches colonized. This new island has a similar plant, Tribulus terrestris, which produces seeds of slightly different sizes and has a different flowering season. Over time, two distinct populations of Geospiza magnirostris evolved: one that continues to feed on Tribulus cistoides and another that exclusively feeds on Tribulus terrestris.
Researchers have noticed that the beak size of the finches has diverged significantly between the two populations. The finches feeding on Tribulus cistoides have retained the ancestral beak size, while those feeding on Tribulus terrestris have developed larger beaks to handle the larger seeds. There is minimal interbreeding between the two populations.
Context on Galapagos finches

Question 1

Multiple choice
The divergence between the two populations of Geospiza magnirostris is likely to have occurred due to which of the following factors?
  • A change in the weather pattern that affected the flowering season of Tribulus cistoides.

  • The introduction of a new food source in the form of Tribulus terrestris seeds on the neighboring island.

  • An increase in predators on the original island of Santa Cruz, forcing finches to migrate.

  • The eruption and subsequent land bridge allowed for gene flow between previously isolated islands.

Question 2

Multiple choice
Which of the following isolating mechanisms is most likely responsible for the limited interbreeding between the two populations of Geospiza magnirostris?
  • Geographic isolation since the finches are now separated by water.

  • Behavioral isolation due to differences in feeding behavior.

  • Gametic isolation due to incompatibility of gametes from the two populations.

  • Temporal isolation due to different flowering seasons of their respective food plants.

Question 3

Multiple choice
Suppose the finches from the two populations do interbreed and produce offspring with intermediate beak sizes. These offspring, however, have lower survival rates because they cannot effectively process the seeds of either Tribulus cistoides or Tribulus terrestris. What kind of selection is illustrated by this scenario?
  • Directional selection favoring specialization in beak size.

  • Disruptive selection favoring either the ancestral or larger beak size.

  • Stabilizing selection favoring intermediate beak sizes.

  • Sexual selection based on beak size attractiveness.

Teach with AI superpowers

Why teachers love Class Companion

Import assignments to get started in no time.

Create your own rubric to customize the AI feedback to your liking.

Overrule the AI feedback if a student disputes.

Other Biology Assignments

Aerobic RespirationAnalyzing Hormone Signaling in CellsAP Biology: Cellular Structure and Organelle FunctionsAP Success - AP Biology Conceptual Analysis: Energetics - Cell StructureAP Success - AP Biology Conceptual Analysis: Energetics - Cellular RespirationAP Success - AP Biology Conceptual Analysis: Energetics - Immune ResponseAP Success - AP Biology Conceptual Analysis: Energetics in Cold-Adapted BacteriaAP Success - AP Biology Conceptual Analysis: Energetics - PhotosynthesisAP Success - AP Biology Conceptual Analysis: Energetics - Thermodynamics and HomeostasisAP Success - AP Biology Conceptual Analysis: Evolution - Biodiversity and EcosystemsAP Success - AP Biology Conceptual Analysis: Evolution - GeneticsAP Success - AP Biology Conceptual Analysis: Evolution - Mathematical Modeling of PopulationsAP Success - AP Biology Conceptual Analysis: Evolution - Natural SelectionAP Success - AP Biology Conceptual Analysis: Evolution - Origins of Cell CompartmentalizationAP Success - AP Biology Conceptual Analysis: Evolution - Species ClassificationAP Success - AP Biology Conceptual Analysis: Info Storage & Transfer -Cell CommsAP Success - AP Biology Conceptual Analysis: Info Storage & Transfer - Cell Cycle (Mitosis & Meiosis)AP Success - AP Biology Conceptual Analysis: Info Storage & Transfer - DNA, RNA, and Gene ExpressionAP Success - AP Biology Conceptual Analysis: Info Storage & Transfer - EndocrineAP Success - AP Biology Conceptual Analysis: Info Storage & Transfer - NervousAP Success - AP Biology Conceptual Analysis: Info Storage & Transfer - VirusesAP Success - AP Biology Conceptual Analysis: Systems Interact - CirculatoryAP Success - AP Biology Conceptual Analysis: Systems Interact - DigestionAP Success - AP Biology Conceptual Analysis: Systems Interact - EcologyAP Success - AP Biology Conceptual Analysis: Systems Interact - EnzymesAP Success - AP Biology Conceptual Analysis: Systems Interact - MusculoskeletalAP Success - AP Biology Conceptual Analysis: Systems Interact - Plant StructureAssignment 1Biodiversity and Cancer Drug DiscoveryBiology - Lab Journal - Yeast MetabolismCell DifferentiationCell Membrane and Transport MechanismsCellular Components and Energy UtilizationCharacteristics of Biological KingdomsDNA - structure and function reviewEcology and Human Impact ReviewEcology AssignmentEnergy Flow in Grassland EcosystemsEnergy Transfer in EcosystemsEnzymesEvidence of Evolution Writing AssignmentExploring the Basics of Biology: A 7th Grade AdventureFrom One to the NextGATTACA Project: The relationship between ethics and genesImmune SystemImmune System BJanuary 2024 Living Environment Regents Written ResponseLab: Catalase enzyme activityMathematics Practice Questions