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 -New Syllabus

IBDP Biology Paper 1 - All Chapters

Question

A bird of paradise (Ptiloris victoriae) has very showy plumage and demonstrates a unique dance. What type of selection pressure could have caused this plumage to evolve?

(A) Interspecific competition
(B) Abiotic factors
(C) Paradigm shift
(D) Sexual selection
▶️ Answer/Explanation

Correct Answer: \( \boxed{\mathbf{D}} \)

Sexual selection favors traits that increase an individual’s chances of attracting a mate. The bird of paradise’s bright plumage and elaborate courtship dance improve mating success, even though these traits may not increase survival. Over generations, sexual selection has led to the evolution of these distinctive characteristics.

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

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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