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Why are bees ecologically important? By Dylan Voeller
and James Nieh I. Principles
introduced in this exercise A. Pollination: the flowers & the
bees B. Importance of native pollinators C. Human agriculture and pollination D. Bees & plant biodiversity II. Introduction Pollen is
produced by a flower’s anthers,
which are at the outer end of the stamen,
the flower’s male sexual organ. A
flower’s female sexual organ is the pistil,
which has an outer sticky end called the stigma (see Fig. 1). When
pollen is transferred from the anther of a flower on one plant, to the stigma
on a flower of another, it is called sexual
reproduction. Sexual reproduction
is advantageous in a constantly changing environment (which most environments
are) because it produces genetically varied offspring (the offspring receive
genes from both the male and female).
Since the ultimate goal of any organism is to pass on the most genes
(or copies of itself), producing diverse offspring will allow those that come
out better suited to their environment to survive and reproduce more than
those that are not as well adapted to their environment. Although some flowers self-pollinate (the
pollen is automatically deposited onto the stigma), most flowering plants
require a pollinator to transfer pollen from the anther of one plant to the
stigma of another. Pollination can be accomplished by many animals such as birds,
insects, and bats;
some species of plants even rely on wind.
Bees are one of the most well known and
important types of pollinator, both in agriculture and natural
ecosystems. Pollination by bees occurs
when a foraging bee brushes against the anthers causing pollen to stick to
her body. When the bee touches the stigma
while searching for nectar at the center of the flower, some pollen grains
are left on its sticky surface. Bees
also use pollen as a food source; it is collected from the anthers into an
area on their legs called the corbiculae,
which contain specialized hairs that hold the pollen in place (see Fig. 1). The flowers of different
plant species often require different behavior by collecting bees. Since plants can’t get up and walk around
to reproduce sexually, many flowers are mellitophilous; they have
coevolved with their pollinating bee species and as a result have specially
designed stigmas and pistils that when foraged by a familiar bee, are more
likely to result in pollination. This
has resulted in specialist bees, which may forage exclusively
on a single type of flower. Despite this
phenomenon, many bees (such as honeybees) are generalists; they have broad food preferences and therefore forage from
many different kinds of flowers. This
phenomenon has been exploited in agriculture, as farmers have imported the
European honeybee (Apis
mellifera), which was domesticated for its
honey production, to pollinate many different crops. However, honeybees
are not efficient pollinators of all crops and wild plants because, as
discussed above, they are generalists and are not always a not always a good
fit for all flower shapes and sizes. The
flowers of most crops are often visited by an assemblage of insects, many
native to a particular region. The importance of these native pollinators
in the reproduction of flowering plants (including those used in agriculture)
is just beginning to be understood.
Unfortunately, there has been a
major decline in native pollinators due in part to habitat loss and
alteration, introduced species, and pesticide use. Habitat loss due to intensive agriculture,
deforestation, and urban development reduces available food resources and
nest sites for native bee species. Declines
in wild bees due to competition for food resources from managed honeybees and
displacement of native plants by introduced plant species have been shown to
have severe effects on overall pollination.
The use of pesticides to control agricultural pests does not
discriminate between pest and pollinator, and is thus also a likely
contributor to the dwindling populations of native pollinators. As a result of this decline in
native pollinators and the spread of disease among domesticated honeybees
(likely a direct result of intense monoculture), there is a current
pollination crisis, both in agriculture and nature. Each
year, bee pollination is vital to millions of It is clear that the
conservation of bees and other pollinators is an urgent issue. Our activities are destroying the diversity
of all wildlife, and having an affect on our own food supply. Clearly a balance between the biodiversity
of natural environments and a system of sustainable agriculture is
needed. Farmers are beginning to turn to native pollinators as a
viable option for crop production however, little is known about the majority of native bees. We must learn more
about the ecology of these species and classify the many unknown pollinating
species in order to assess the role of bees and other insects in pollination
and put them to use in sustainable agricultural systems. III. Discussion questions & activities A.
Can
you identify foods that you eat that are bee pollinated? B.
Come
up with a menu of what your family eats for dinner during a typical
week. Write it up on the board, divided
into categories (fruits, vegetables, dairy, meats, grains, etc.). Then
subtract all of the foods that are bee pollinated. Remember, many cattle are fed on crops such
as alfalfa and clover! Pollination can
therefore affect things such as the supply of meat and milk. After you have
subtracted out all the bee-pollinated foods, try to come up with a new
menu. What would you eat in a world
with no bees?
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