13.2: The Classification of Plants
- Page ID
- 133700
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Plants are a large, versatile, and varied group of organisms with over 300,000 known species on Earth. With so many different types of plants, we must organize them into groups that make sense. Plants can be classified based on their tissues, reproductive methods, and more. Let’s take a look at some of the larger categories of plants and the characteristics that make each group unique.
The Bryophytes -- Nonvascular Plants
Mahieddine Boumendjel, CC BY-SA 3.0, via Wikimedia Commons
The bryophytes are nonvascular plants and the simplest of land plants.There are three groups within the bryophytes: the hornworts, the liverworts, and the mosses. Nonvascular plants do not have any specialized vascular tissue to conduct water through the plant, nor do they produce seeds. Instead, bryophytes absorb water via osmosis and produce water-dependent gametes. This means that most bryophytes must remain close to moisture otherwise they may quickly dry out.
Bryophytes also do not have true leaves, stems, or roots. Without these structures, the bryophytes are also stuck to being very small. Because of their simplicity, the bryophytes come across as the most “ancient” of the plants.
The Ferns -- Seedless Vascular Plants
In this group of plants, we now see vascular tissue -- xylem and phloem -- that help transport fluids around the plant. We also see true leaves, stems, and roots as well, meaning that these plants are no longer limited in size like their bryophyte cousins. These are the ferns -- a group of plants that includes true ferns, club mosses, and horsetails. Additionally, ferns reproduce using spores instead of swimming gametes, although these spores do still need a moist environment to function. These spores are formed in the sori, which are found on the underside of the fern’s fronds.
The Gymnosperms -- Seeded Plants
"Hikers Under a Giant Sequoia Tree" by Karen Marks, Reedley College is licensed under CC BY 4.0
One of the greatest evolutionary leaps made by plants was the development of the seed. Compared to their seedless cousins, seed-bearing plants were able to conquer areas that were much warmer and drier. Seeds provide a protective and nourishing coating around the embryonic stage of the plant, meaning that the developing plantling is not limited to moist, shady environments. The first plants to develop seeds were the gymnosperms. The gymnosperms are a very diverse group consisting of the conifers, gnetophytes, cycads, and ginkgophytes. These plants vary greatly in their physical appearance as well as where they grow, ranging from the warm tropics to the cold, high altitude mountains. Some of the largest organisms found on the planet belong to the gymnosperms. If you look closely at the image on the right, you’ll see just how big they can be!
The Angiosperms -- Flowering Plants
Calimo, CC BY-SA 3.0, via Wikimedia Commons
The newest and most successful group of plants in modern day are the angiosperms. The angiosperms are the flower-producing plants and with over 260,000 different species, they now dominate the plant world.
Flowers are specialized structures originally modified from leaves. Their primary use is for reproduction, with the male and female reproductive organs found within. Many angiosperms rely on pollinators to help distribute the male gametes. Once the female gamete has been fertilized, a fruit begins to form around the developing seed. This fruit is used to reward animals who eat it and then (unknowingly) distribute the seeds through their feces.