Answer 1:
One of the cool things about science is that
sometimes you can figure out the answer to
something you don't know by thinking about it in
terms of things you do know. Conifers, holly, and
oaks are very specific types of plants. It might
take a lot of time looking through books to find
something that says how each of these particular
plants disperses its seeds. However, if you look
at the question in a more general sense, and then
consider what you do know about these plants, you
can make a very good guess as to how these plants
probably disperse their seeds.
First, how
many ways can you think of that a plant could
disperse its seeds? There are many believable
possibilities. Maybe a plant could have its
seeds blown far away by the wind. Maybe
its seeds could fall in the water and be
carried away by a river or stream, or float across
a lake or ocean. Maybe the plant could
somehow "throw" or "shoot" the seeds. Maybe
the seeds could be moved places by
an animal, either because the seeds got stuck
to it or because the animal carried them on
purpose. You might think of even more ways a seed
could get moved somewhere.
Now that you've thought of some ways a seed
might get moved, the next thing to do is to think
about what you know about the seeds of conifers,
holly, and acorns, and from that determine which
of the above seed dispersal mechanisms seems the
most likely.
Conifers produce their seeds inside
cones (ie, pine cones). A pine cone probably
couldn't be blown very far by the wind while it
falls, unless the seeds were to come out of the
cone and get blown somewhere before the cone fell.
However, seeds that are dispersed by wind
normally have shapes that help them get carried in
air, such as tufts of "hair" or wings. A pine
cone could certainly be transported by water, but
the problem with that idea is that conifers are
land plants, and can't really grow in the water.
So the seed might drown in the water, and the
conifer couldn't grow unless the pine cone were to
somehow get pushed or pulled out of the water and
onto the land. I've seen lots of pine trees
growing far away from water, so this doesn't seem
like a very likely mechanism. I've also never
seen pine cones shooting seeds out, so this
doesn't seem like a likely dispersal mechanism
either. I have, however, seen birds pecking at
pine cones, and people kicking them. It makes a
lot of sense, then, that birds or people or maybe
even other animals could be moving the pine cones,
or the seeds that are in them.
Going through a similar thought process with
acorns and holly, it seems evident that they
wouldn't be transported by wind, water, or
launching. However, holly produce nice red
berries (which we've all seen in Christmas
decorations) that look like they might be awfully
tempting to animals, especially birds.
Why would a plant produce something tasty
for animals to eat? It doesn't
seem like it would benefit a plant to get eaten,
unless it produces the fruit to attract an animal
so that the animal will transmit its seeds. This
certainly makes sense, since even we humans throw
the seed (or pit) away after we eat a piece of
fruit-- effectively dispersing the seed (have
you ever bitten into a grape with seeds in it?
The first thing you do is spit the seeds back out
on the ground!). Acorns also don't look
well-suited to any of the forms of transport
except for by animals. Chipmunks (like the Disney
characters
Chip and Dale) and squirrels like to hide acorns
in order to store them for later, and sometimes
they might forget where they hid them, allowing
them to grow into new plants. Birds and other
animals might also try to eat acorns, carrying
them away from the tree in the process. Birds,
such as the blue jay, can carry acorns especially
long distances since they can fly.
So it seems likely that the most important
mechanism of seed dispersal for all three of these
plants is transport by animals. (This also
includes the deliberate planting of seeds by
people!
If you plant a tree in your yard or
vegetables in your garden, you have transported
some seeds!) This doesn't mean that other
mechanisms aren't also at work. Sometimes a
strong wind might blow a seed, or a seed might
fall into the water and later get washed up on
land. But the most common method of
dispersal is through animals. |
Answer 2:
Seeds of conifers, holly and oaks (acorns) may
be dispersed directly from the plants by
dropping when fruits mature. Some of these
seeds and fruits may roll, or be blown along the
ground. Some conifer seeds have seed wings, which
increase the chances that they will be moved by
wind.
Fruits and/or seeds of these
plants may also be dispersed by animals. Fruits
and berries may be eaten by a variety of animals.
Many fruits have indigestible seeds, which pass
through the animals digestive tracts.
Squirrels, Pigeons, Jays and
Woodpeckers may even plant the seeds
inadvertently. These animals store some of their
fall harvests for food in the winter. The seeds
may germinate from buried caches
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