Organisms belonging to the kingdom
Plantae are autotrophic. Which of the following best
explains what this means? (A) Autotrophic organisms obtain
their food through consuming other organisms. (B) Autotrophic organisms can
produce their own food using inorganic materials. Or (C) autotrophic organisms are
able to grow in nutrient-free environments.
Our question deals with organisms
within the kingdom Plantae, the plants. This kingdom includes not only
familiar types of plants, such as pine trees, tulips, and cacti, but also lesser
known groups, such as the liverworts and whisk ferns. It is worth noting that based on
molecular data, many scientists have adopted an expanded version of kingdom Plantae
that includes red and green algae, although this continues to be debated.
If you have ever taken care of a
plant, you already know that they don’t need to be fed the same way that humans do
or that a pet might. They do require some basic
nutrients, which they get from soil, as well as water, air, and sunlight. But how do plants use these
materials to make the energy they need to grow and reproduce? Plants are able to produce their
own food through photosynthesis, a process that uses the energy from sunlight to
produce glucose and oxygen from water and carbon dioxide. The reactants of the photosynthesis
equation are carbon dioxide and water. Neither of these molecules contain
carbon–hydrogen bonds, so they are inorganic substances.
During photosynthesis, structures
inside of plant cells called chloroplasts will use energy from photons of light to
initiate the conversion of inorganic carbon dioxide and water into the organic
compound glucose, releasing oxygen in the process. Glucose is then used to make more
organic molecules, including starch, cellulose, amino acids, and lipids. It also powers cellular respiration
to create energy in the form of ATP.
Looking at the term autotroph, you
may recognize the prefix auto-, which means self, and the root word -troph, which
means nourishment or food. Because plants are able to produce
their own food source through photosynthesis, they are classified as autotrophs. Organisms that produce their own
food through chemosynthesis, which relies on energy from the oxidation of inorganic
molecules rather than light energy, are also categorized as autotrophs.
In contrast, organisms that cannot
produce their own organic compounds are known as heterotrophs. The prefix hetero- means other, and
we already know that -troph means food. So, heterotrophs get their
nourishment from consuming other organisms instead of making it themselves like
Now that we have covered the
difference between autotrophs and heterotrophs, let’s take a look back at our
question. It asks us for the best explanation
of autotrophs. And we’ve just learned that
autotrophs are organisms, like plants, that are able to produce their own food from
inorganic substances. So, the correct answer to our
question is (B). Autotrophic organisms can produce
their own food using inorganic materials.