L1
讲座
1. What is the lecture mainly about?
Research that attempts to explain why dark birds are more common in urban areas than light birds are
Reasons why pollution negatively affects dark birds more than it does light birds
A study investigating trace metals in different urban environments
Ways that melanin contributes to a bird’s choice of habitat
2. According to the researchers, how can melanin benefit birds?
It helps birds to digest trace metals in their food.
It moves metal particles to growing feathers.
It allows birds to grow new feathers quickly.
It allows birds to blend in with their environment.
3. What did the study reveal about the concentrations of trace metals in the birds’ feathers after one year?
Only light birds were able to store lead in their feathers.
There was no link between degree of coloration and lead concentration.
The concentrations of trace metals were higher than when the birds were originally captured.
The feathers of dark birds contained more zinc than those of pale birds.
4. Why does the professor mention how often birds shed their feathers?
To explain why researchers sometimes had difficulty identifying individual birds
To point out that birds can appear darker at different times of the year
To express doubt about the conclusions of the study
To suggest that birds in polluted areas shed their feathers more often than other birds
do
5. The professor mentions a possible follow-up study. How would the study that she proposes differ from the original study?
The birds would be kept in an urban environment during the study
Many species of birds would be studied.
Measurements of trace metal concentrations would be taken from the birds’ blood.
The researchers would examine more types of trace metals in the study
6. What does the student imply when he says this:
He is surprised that the researchers collected birds from areas that were close together.
He is doubtful about whether the researchers chose the best city to collect birds.
He is impressed that the researchers could find so many different colors of pigeons.
He is confused by the results of the initial tests conducted by the researchers.
