Video Transcript
The diagram provided shows how a
pollinator pollinates a plant, which means that it transports the male sex cells
contained in pollen from the anther of a flower to the stigma of either the same or
another flower. This plant is therefore an
insect-pollinated plant. Which of the following does not
describe an adaptation that is useful for an insect-pollinated plant? (A) The pollen produced is sticky
or spiky. (B) Flowers contain a sweet sugary
fluid called nectar. (C) Flowers have large and brightly
colored petals. Or (D) the anthers and stigma hang
loosely outside of the flower.
Insect pollinators, like bees and
butterflies, can be really helpful to many species of flowering plants, as they are
able to fairly efficiently transfer pollen across long distances. Pollen grains, which contain the
male sex cells of a flowering plant, are produced in parts of the flower called the
anthers. The stigma is a part of the
flower’s female reproductive organ. The stigma leads down to an ovary
that contains one or more female sex cells, egg cells.
As we are told in the question,
pollination is the process of transferring pollen from an anther to a stigma. This allows a male sex cell to
eventually fertilize a female sex cell in the ovary. Let’s take a look at some of the
typical adaptations of insect-pollinated flowers so that we can work out which of
the answer choices would not be useful for this mode of pollination.
Some insect-pollinated flowers
produce a sugary fluid called nectar, which entices insects to the flower,
especially bees, which use nectar to make honey. When insect pollinators, like the
bee in the image provided to us in the question, visit flowers to access nectar,
some pollen usually rubs off the anthers and onto the insect’s body. When the insect visits another
flower, the pollen, which you may remember contains the male sex cells, can rub off
the pollinator’s body and onto this second flower’s stigma. With what we have learned so far,
we can eliminate answer option (B): flowers contain a sweet sugary fluid called
nectar. We know that this flower adaptation
is useful for some insect-pollinated plants.
How does an insect know that a
flower might contain nectar? Well, insect-pollinated flowers
tend to have especially large and brightly colored petals, which advertises that
this flower might have nectar for the insect to eat. With this information, we can
eliminate answer choice (C): flowers have large and brightly colored petals.
In insect-pollinated flowers, the
anthers and stigma are often found inside the flower, in front of the nectar. This enables the anthers to deposit
as much pollen as possible onto pollinators’ bodies when they make contact with the
flower. It also makes it more likely that
pollen which is already on the insect’s body will land on the stigma. This suggests that the correct
answer is likely to be option (D): the anthers and stigma hang loosely outside of
the flower. This would not be helpful in
depositing pollen on an insect’s body, nor would it be helpful to deposit pollen
from their body onto a stigma. Instead, insects might bypass these
structures entirely if they are located outside the flower.
Let’s check answer option (A) — the
pollen produced is sticky or spiky — to confirm our choice. Sticky or spiky pollen would be a
helpful flower adaptation for an insect-pollinated plant. Sticky or spiky pollen is more
likely to attach to an insect’s body.
Therefore, we can confirm that the
correct answer to this question is (D). The anthers and stigma hang loosely
outside of the flower.
