IB DP Biology- D4.1 Natural selection- IB Style Questions For HL Paper 1A -FA 2025
▶️ Answer/Explanation
✅ Answer: (C) Predation influences the colour of guppies in different environments.
Question
▶️Answer/Explanation
A cladogram is a branching diagram that shows the evolutionary relationships between different species. The closer two species are on the diagram, the more recently they shared a common ancestor.
Evaluation of Each Option:
A. Incorrect – Baboons do share a common ancestor with gorillas, humans, and chimpanzees, though the split occurred earlier. All species on a cladogram ultimately trace back to a common ancestor.
B. Correct – Humans and chimpanzees appear closest together on the cladogram, meaning they share the most recent common ancestor compared to gorillas and baboons.
C. Incorrect – The baboon is one of the species on the cladogram, not the common ancestor. The common ancestor is represented by the node from which all four species branch.
D. Incorrect – Evolutionary splits shown on a cladogram do not represent equal time intervals unless explicitly stated (which is rare). Branch length doesn’t necessarily mean equal timing.
Question
A central idea in the theory of evolution is that species may evolve gradually over time from a common ancestor.
I. Beak shape shows genetic variability in the common ancestor.
II. Changes in beak shape that occur during the lifetime of an individual bird are passed on to the next generation.
III. Changes in beak shape are heritable and make each species better adapted to its environment.
▶️Answer/Explanation
How does evolution explain the development of different traits (like beak shape)?
Evolution by natural selection involves heritable genetic variation. Individuals with traits better suited to their environment are more likely to survive and reproduce, passing those traits to the next generation. Importantly, acquired traits (like changes that happen during an organism’s lifetime) are not inherited.
Evaluation of Statements:
I. Correct – Genetic variation in the beak shape would have existed in the original population (common ancestor). Natural selection acts on this variation.
II. Incorrect – This reflects the outdated Lamarckian idea that traits acquired during an individual’s life (like muscles or beak wear) are inherited. Modern biology shows that only genetic traits are passed on.
III. Correct – Changes in beak shape are due to genetic differences. If these differences help a bird survive and reproduce, they are passed on, making the population better adapted over time.