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Classifying Living Things: The Plant Kingdom
What features distinguish plants from other life
forms?
Plants are eukaryotic organisms, meaning their
cells contain nuclei as well as organelles. They are multicellular
and have
the ability to make their own food. Plant cells are different
from animal cells
because they have a cell wall.
The cell wall, made of a compound called cellulose, gives structural
support to plants, allowing
them to stand
tall. Plant cells are also unique from animal cells in that they
contain an organelle called chloroplast, where they use the energy
from sunlight
to convert carbon dioxide and water into food during the process
of photosynthesis. A chemical in chloroplasts that is involved
in photosynthesis — chlorophyll — is
what gives plants their green color.
Leaf (inset) and leaf cells.
Roll your mouse over the word "cell
wall" to highlight this structure.
How are plants important
to people?
As well as being important food sources, plants
are well known as a source of many important chemicals that are used
in
medicine,
cosmetics, and agriculture. Because land plants are unable to
move, they have evolved multiple adaptations to facilitate their
success and ability to thrive in a range of ecosystems. For instance,
many
plants produce pesticides to protect themselves from insects.
These pesticides have practical uses for humans. In fact, caffeine
is technically
a pesticide! Other chemicals may be toxins to dissuade larger
animals from eating the plant leaves or fruits. Conversely, some
chemicals
are actually produced to attract animals — the scents of flowers
are good examples. Other ways of attracting animals include special
colors and shapes of flower and leaf parts as well as nectar
production. The purpose of these enticements is to encourage animals
to stop by
and eat, ultimately leading to pollination of the flowers and
increasing reproductive output.
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