L2
讲座
1. What does the professor mainly discuss?
Why male hummingbirds are generally smaller than female hummingbirds
Why most flowers on St.Lucia are pollinated by only one species of hummingbird
Why sexual dimorphism is more common among hummingbirds than among other bird species
Why the beaks of male and female hummingbirds of a particular species are shaped differently
2. What does the professor imply about Darwin’s work?
It contained the first scientific observations of the purple-throated carib hummingbird
It suggested that sexual dimorphism is always related to attracting a mate
Darwin did more work with animal evolution than with plant evolution.
One of Darwin’s hypotheses could not be confirmed until recently.
3. Why is the carib hummingbird on St.Lucia a useful species for researchers to test the hypothesis that feeding habits can lead to sexual dimorphism?（多选题）
The carib is the only species on St.Lucia that collects the nectar of H.caribaea and H.bihai.
The carib’s habitat has not been disturbed by human activity
The carib’s bright colors make it easy to locate and observe in the wild
The carib’s sexual dimorphism is more pronounced than that in other species of hummingbirds.
4. What did researchers conclude from measuring the amount of time that male and female caribs spent feeding?
Their beaks help the caribs feed efficiently.
Male and female caribs require different amounts of nectar.
Female caribs take longer than male caribs to collect nectar
H.caribaea produces the most flowers in areas where the caribs feed the longest
- Why does the professor mention that in parts of St.Lucia,H.bihai flowers have developed two different shapes?
To suggest that H.bihai may be pollinated by both insects and hummingbirds
To introduce an additional aspect of the relationship between the carib and H.bihai
To emphasize the difference in body size between male and female caribs
To point out that sexual dimorphism is widespread among flowering plant species
- What does the professor say regarding the debate about the evolution of flowers and caribs on St, Lucia?
She needs more data before forming an opinion.
She believes it is unreasonable to expect a clear resolution to the debate.
Those involved in the debate are failing to consider Darwin’s hypothesis
The flowers and caribs probably evolved independently of each other.
