Question

standard 4 natural selection & adaptations
inquiry question: how do environmental changes drive adaptations in populations?
reading:
in the 1800s, industrial pollution darkened tree bark in england, leading to an increase in dark - colored moths. the lighter - colored moths, once common, became more visible to predators and declined in number. this is an example of directional selection in response to environmental change.
data: frequency of light vs. dark moths over time

year	light moths (%)	dark moths (%)
1850	60%	40%
1900	20%	80%
1950	10%	90%

multiple - choice questions:

1. what pattern does the data suggest?

a) light moths increased over time
b) dark moths became more common as pollution increased
c) moth populations remained stable
d) both light and dark moths disappeared

1. what would happen if pollution were reduced?

a) light moths would become more common again
b) dark moths would continue to dominate
c) no change in moth population
d) moths would go extinct

Explanation:

Step1: Analyze data trend

From 1800 - 1950, light moths percentage decreased from 90% to 10%, and dark moths percentage increased from 10% to 90% as pollution (darkening of tree - bark) increased.

Step2: Consider pollution reduction

If pollution is reduced, tree - bark will lighten, and light moths will have a survival advantage again.

Answer:

1. b) Dark moths became more common as pollution increased
2. a) Light moths would become more common again