1. In a graph showing directional selection, what usually happens to the peak of the trait distribution after selection?
A.
It shifts toward one extreme value
B.
It remains exactly at the same value
C.
It becomes wider on both sides equally
D.
It disappears completely
Correct Answer:
It shifts toward one extreme value
Explanation:
In directional selection, individuals with one extreme phenotype are favored, so the graph's peak shifts toward that extreme.
2. What does the horizontal axis usually represent in a graph of directional selection?
A.
Number of generations
B.
Phenotypic value of the trait
C.
Amount of food available
D.
Population size
Correct Answer:
Phenotypic value of the trait
Explanation:
The horizontal axis of a directional selection graph commonly shows the range of phenotypic values for a particular trait.
3. What does the vertical axis usually represent in a directional selection graph?
A.
Frequency of individuals
B.
Temperature of the habitat
C.
Age of individuals
D.
Number of genes in a cell
Correct Answer:
Frequency of individuals
Explanation:
The vertical axis generally shows how frequently individuals with different trait values occur in the population.
4. A graph shows the population peak moving toward larger body size over generations. Which type of selection does this graph indicate?
A.
Directional selection
B.
Stabilising selection
C.
Disruptive selection
D.
Random mating
Correct Answer:
Directional selection
Explanation:
A shift of the population distribution toward larger values indicates that one extreme, larger body size, is being favored.
5. In a directional selection graph, which phenotype is generally favored?
A.
One extreme phenotype
B.
Only the average phenotype
C.
Both extreme phenotypes equally
D.
All phenotypes equally
Correct Answer:
One extreme phenotype
Explanation:
Directional selection favors one extreme of a trait, causing the distribution to shift in that direction.
6. If the peak of a graph shifts from shorter beaks to longer beaks, what does the shift show?
A.
The average beak length has increased
B.
The average beak length has decreased
C.
All beak lengths have become equal
D.
Beak length is no longer inherited
Correct Answer:
The average beak length has increased
Explanation:
A shift of the peak toward longer beaks shows that the population average has moved toward the longer-beak extreme.
7. Which graph pattern best represents directional selection?
A.
A bell-shaped curve shifted toward one side
B.
A curve becoming taller and narrower around the average
C.
A curve developing two peaks at both extremes
D.
A flat line with no variation
Correct Answer:
A bell-shaped curve shifted toward one side
Explanation:
Directional selection changes the distribution by shifting its peak toward one extreme of the trait range.
8. In a directional selection graph, what does an arrow pointing toward the right usually indicate?
A.
Selection favors higher trait values
B.
Selection favors lower trait values
C.
Selection favors only average values
D.
Selection has stopped acting
Correct Answer:
Selection favors higher trait values
Explanation:
If higher trait values are shown on the right, a rightward shift indicates that individuals with higher values are being favored.
9. A directional selection graph shows the population curve moving toward smaller seeds. What is being selected for?
A.
The smaller-seed extreme
B.
The larger-seed extreme
C.
Only medium-sized seeds
D.
Equal numbers of all seed sizes
Correct Answer:
The smaller-seed extreme
Explanation:
Movement of the curve toward smaller seeds means that the smaller-seed phenotype has a selective advantage.
10. What is the main visual feature of a directional selection graph across generations?
A.
A shift in the distribution toward one extreme
B.
A complete loss of the population curve
C.
Two equal peaks appearing at both extremes
D.
No change in the position of the curve
Correct Answer:
A shift in the distribution toward one extreme
Explanation:
The defining graph pattern of directional selection is movement of the trait distribution toward one end of the range.
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