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9.2: Importance of Plants

Difficulty Level: At Grade Created by: CK-12
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What is so special about this particular plant?

Look at this plant. You could say it has some interesting fruit. Some might say the fruit does not even look that tasty. However, this is a cacoa tree, and its seeds are the source of chocolate. So, there are some people who would argue that this is one of the most important plants in the whole plant kingdom.

The Importance of Plants

The importance of plants to humans and just about all other life on Earth is staggering. Life as we know it would not be possible without plants. Why are plants so important?

  • Plants supply food to nearly all terrestrial organisms, including humans. We eat either plants or other organisms that eat plants.
  • Plants maintain the atmosphere. They produce oxygen and absorb carbon dioxide during photosynthesis. Oxygen is essential for cellular respiration for all aerobic organisms. It also maintains the ozone layer that helps protect Earth’s life from damaging UV radiation. Removal of carbon dioxide from the atmosphere reduces the greenhouse effect and global warming.
  • Plants recycle matter in biogeochemical cycles. For example, through transpiration, plants move enormous amounts of water from the soil to the atmosphere. Plants such as peas host bacteria that fix nitrogen. This makes nitrogen available to all plants, which pass it on to consumers.
  • Plants provide many products for human use, such as firewood, timber, fibers, medicines, dyes, pesticides, oils, and rubber.
  • Plants create habitats for many organisms. A single tree may provide food and shelter to many species of insects, worms, small mammals, birds, and reptiles (see Figure below).

Red-eyed tree frogs like this one live in banana trees.

We obviously can’t live without plants, but sometimes they cause us problems. Many plants are weeds. Weeds are plants that grow where people don’t want them, such as gardens and lawns. They take up space and use resources, hindering the growth of more desirable plants. People often introduce plants to new habitats where they lack natural predators and parasites. The introduced plants may spread rapidly and drive out native plants. Many plants produce pollen, which can cause allergies. Plants may also produce toxins that harm human health (see Figure below).

Poison ivy causes allergic skin rashes. It’s easy to recognize the plant by its arrangement of leaves in groups of three. That’s the origin of the old saying, “leaves of three, leave it be.”

Why Study Plants?

Members of the plant kingdom play many crucial and sometimes surprising roles in the drama of life on Earth. You are probably familiar with some reasons plants are important. Why should you understand how plants live? Because plants play many roles, including but certainly not limited to:

  1. Supplying Food and Energy
  2. Maintaining Earth’s Atmosphere
  3. Cycling Water and Nurturing Soils
  4. Contributing to Nitrogen and Other Biogeochemical Cycles
  5. Interdependence with Animals
  6. Interdependence with Fungi
  7. Interdependence Among Plants
  8. Resources for Humans
  9. Aesthetics for Humans
  10. Scientific Use by Humans
  11. Causing Problems


  • Life as we know it would not be possible without plants.


Use this resource to answer the questions that follow.

  • http://www.hippocampus.org/Biology\begin{align*}\rightarrow\end{align*} Biology for AP* \begin{align*}\rightarrow\end{align*} Search: Plants and Their Relatives: Overview
  1. Why are plants important?
  2. Discuss the importance of agriculture.
  3. What were probably the first plants on land?
  4. What are photoautotrophs?


1. List reasons that plants are important to life on Earth.

2. When is a plant considered a weed?

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weed Plant that grows in unwanted places.
pollen Tiny grains that bear the male gametes of seed plants and transfer sperm to female reproductive structures.
photosynthesis Process of using the energy in sunlight to make food (glucose).

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Difficulty Level:
At Grade
Date Created:
Feb 24, 2012
Last Modified:
Sep 04, 2016
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