Life Science: Session 2
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.
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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