Home / IB DP Biology- D4.1 Natural selection – IB Style Questions For SL Paper 1A

IB DP Biology- D4.1 Natural selection - IB Style Questions For SL Paper 1A -FA 2025

IBDP Biology Paper 1 - All Chapters

Question

In a series of studies, Mark investigated sexual and natural selection in Trinidadian guppies (Poecilia reticulata) by varying environmental conditions and predation pressure.

What conclusion was drawn from Mark’s experiments?

A. Guppies have no predators in their native streams.
B. Male guppies show preference for dull-coloured females.
C. Predation pressure determines the colour patterns of guppies in different habitats.
D. Guppies remain unaffected by the presence of other fish species.

▶️ Answer/Explanation
Mark’s research showed that predation plays a key role in guppy colour variation. In areas with high predation, males evolved duller colours for better camouflage, while in low-predation environments, males displayed brighter colours to attract mates. This demonstrates the interaction between natural and sexual selection in evolution.
✅ Answer: (C) Predation influences the colour of guppies in different environments.

Question

The cladogram shows the evolutionary relationships between a number of animal groups.

What can be concluded from this cladogram?

A. Tuna evolved from sharks.
B. Crocodiles are more closely related to birds than to whales.
C. Frogs, humans and whales do not share a common ancestor.
D. Shark and tuna evolved later than humans

▶️ Answer/Explanation

Answer: B. Crocodiles are more closely related to birds than to whales

Explanation:
A cladogram depicts evolutionary relationships based on shared common ancestors. Taxa that share a more recent common ancestor are more closely related. In the diagram, crocodiles and birds branch from a more recent node than either does with whales, indicating closer relationship (both are archosaurs).

Answer Evaluation:

A. Incorrect — Tuna and sharks share an ancient common ancestor but one did not evolve directly from the other; they are separate fish lineages.
B. Correct — Crocodiles and birds share a more recent common ancestor than either shares with whales, so they are more closely related to each other.
C. Incorrect — Frogs, humans, and whales all share a distant common ancestor as vertebrates; the cladogram shows common ancestry.
D. Incorrect — Sharks and tuna represent older fish lineages; humans evolved later from terrestrial vertebrate ancestors.

Question

Darwin described evolution as “descent with modification”. What would make evolution less probable?

A. Stable environment
B. Migration
C. Variation in offspring
D. Random mutation

▶️ Answer/Explanation

Answer: A. Stable environment

Explanation:

  • Evolution is the process by which populations change over time through natural selection acting on heritable variation. For evolution to occur, environmental pressures must favor certain traits over others.
  • In a stable environment, selective pressures remain constant. Organisms already well adapted to their environment are less likely to change, which reduces evolutionary progress.
  • By contrast, migration, genetic variation, and mutations introduce new traits and gene combinations, increasing the likelihood of evolution when environmental conditions shift.

Answer Evaluation:

A. Correct – A stable environment reduces selective pressures, decreasing the need for adaptation and evolution.
B. Incorrect – Migration introduces new genetic material into a population, enhancing diversity and evolutionary potential.
C. Incorrect – Variation in offspring provides the raw material for natural selection and evolutionary change.
D. Incorrect – Random mutations introduce new genetic traits that can be favored or removed by natural selection.

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