Hummingbirds can have different beak lengths.

Question

They use their beaks to reach to the nectar (their food) at the bottom of flowers. Hummingbirds with longer beaks can get food from long flowers. Hummingbirds with shorter beaks cannot reach the nectar in long flowers. If a hummingbird can’t easily reach its food, it will die.

The diagrams below show three possible hummingbird populations.

Diagram titled Population 1 containing a row of 8 hummingbird icons labeled Short.
Diagram titled Population 2 containing 2 rows of 4 hummingbird icons each, one labeled Short and one labeled Long.
Diagram titled Population 3 containing a row of 8 hummingbird icons labeled Long.
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2. If their environment changes to have only long flowers, which of the following hummingbird populations will most likely survive?
Responses

a
Only population 2 will survive because it is the only population with variation.
Only population 2 will survive because it is the only population with variation.

b
All the populations will survive because the hummingbirds will change the length of their beaks if they need to.
All the populations will survive because the hummingbirds will change the length of their beaks if they need to.

c
Populations 1 and 2 will survive.
Populations 1 and 2 will survive.

d
Populations 2 and 3 will survive.

Answer 1

The most likely response is:

d Populations 2 and 3 will survive.

Here's the reasoning:

• Population 1 consists entirely of short-beaked hummingbirds, so they would not be able to reach the nectar in the long flowers and would likely die off.
• Population 2 has both short and long-beaked hummingbirds. The long-beaked hummingbirds can access the nectar in the long flowers, which means at least some individuals from this population will survive.
• Population 3 consists entirely of long-beaked hummingbirds, so they will also be able to reach the nectar and survive.

Thus, only populations 2 and 3 are likely to survive under the new conditions with only long flowers.