| Many of the free
services that are provided by ecosystems are dependent upon plants.
But plants themselves are dependent upon other animals or environmental
factors for their survival. The environment provides nutrients,
water, and energy to make individuals grow, but plants also need
help in order to reproduce themselves. This is one way that plants
are very different than animals. Animals are able to move and
perform other behaviors that allow them to search out their mates
and reproduce. Because plants can’t move, they must rely
upon animals, water, or wind to carry their reproductive cells
from one plant to another and help mating to occur.
When plants, like trees, can live for hundreds of years, we sometimes
take for granted the idea that they will always be there. If plants
cannot successfully produce offspring, our forests or our favorite
tree near our home or school will just be like a living dinosaur.
Before long, it would be extinct.
How does this free service work? Plants produce two different
kinds of cells, female cells or eggs, and male cells or pollen.
Pollen is produced in a special part of the flower called the
anther and must move to another flower, and land on a part called
the stigma. The pollen opens up on the stigma and travels down
into the ovary where it joins with the egg. The egg develops into
a seed and the whole ovary matures into a fruit.
Fruits can take many forms such as a fleshy fruit, a nut, or
a capsule. How does the pollen move from one plant to another?
The flower part called the anther opens up to make the pollen
accessible to animals, such as insects, birds, bats, and mice,
or to wind or water.
On animals, the pollen is picked up on a part of the body and
then when the animal visits another flower, it brushes against
the sticky female flower part, the stigma. The pollen gets left
behind. For the water and wind, the pollen is carried away and
moves through the environment. Much of the pollen gets lost, deposited
on leaf surfaces, sidewalks, or grass. But a small fraction actually
does reach another flower of that species and so it is able to
produce a seed.
Why do the animals visit the flowers? Plants provide rewards for
the animals. Usually nectar is what most animals want since it
provides sugar that is a source of energy for them. Some animals,
such as bees, also collect pollen from the plant, which they use
as a source of protein which is fed to their developing young.
It is important to remember that without pollination, most of
the food for people and many other animals would not be produced.
We would have no corn, rice, or wheat, no apples, avocadoes, or
strawberries, no tomatoes, green beans, or pumpkins. Squirrels
would have no acorns, mice would have no grass seeds, birds would
have no sunflower seeds, bears would have no wild berries to eat.
Pollination is another example of how all parts of the ecosystem
are dependent upon one another to survive.
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The Pollination Department is run by Suga and her
6 “b” helpers. There are the bees who pollinate more
flowers than anyone, the butterflies whose long tongues reach
into the flowers which are too deep for the bees, birds (as in
hummingbirds) pollinate many flowers with their long beaks and
tongues, bats help out the night flowering plants, beetles take
care of the low growing ground flowers and the breeze is the sixth,
and sometimes forgotten helper.
It is possible to see the pollination department at work almost
year round. The summer is the busiest season, but even in winter
some plants begin to flower and produce seeds. Ferns and mosses
take advantage of wet weather; raindrops splash the male cells
on one plant to the egg cells on another. To see the department
at work, take the children out and see how many plants they can
find that are flowering. See if they can identify some of the
plant parts, in particular the anthers, pollen and stigma. Also
see if they can find any fruits that are developing on the plant. |
