Seed dispersal lesson nature of seed table
Answers
Most of the plants we’re familiar with start out as seeds. Seeds are alive, but are in a dormant
state in which they do not grow or develop until certain environmental conditions are met. At
that point the seeds germinate, or sprout. A typical seed is made up of three parts: a protective
outer shell called the seed coat, a small embryonic plant called the embryo, and a food packet
that will sustain the growing sprout until it reaches sunlight and is able to begin photosynthesis.
This food packet is called the endosperm. Seeds typically remain dormant through the winter
and germinate in the spring, when the two main conditions for germination, namely warmth and
moisture, are met. However, if a seed is stored in cool, dry conditions, it can remain viable for
decades or even centuries. Some seeds have additional criteria before germination can occur,
such as heat treatment or scorching, or scratching the outer seed coat, but for the seeds of most
familiar plants, warmth and moisture are all that is required.
Plants are immobile, but it is to the plant specie’s advantage to spread its seeds widely. A plant
population that exists solely within a limited geographic area can be wiped out by things like
drought, disease or a harsh winter. In addition, tall plants such as trees require that their seeds
be moved away from the parent plant in order to have enough room and sunlight to grow to
maturity. But since the plants themselves are unable to move, they are forced to rely on some
mechanism for moving the seeds away from themselves. We call this movement of seeds away
from the parent seed dispersal.
There are three main types of seed dispersal: animal, wind, and water.
Seeds can be dispersed by animals in a variety of ways. Many plants develop their seeds inside a
fruit of some kind. When the animal eats the fruit, it also eats the seeds. The seed coat protects
the seed from being digested. The seed passes through the animal’s digestive system unharmed,
and ends up being deposited with the animal’s feces. Since animal feces makes good fertilizer for
plants, the seed has been moved to another place and then deposited with fertilizer to help it
grow. Other seeds, like the sticker burrs common in Texas, have tiny spikes or hooks on them.
These catch on the feathers and fur of animals and are carried away from the parent plant before
falling off. Seeds can also be dispersed by animals such as squirrels, who bury so many acorns
that they never find them all.