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Unit A: Continuity of Life
Chapter 1:
Classification of Living Things
Lesson 2 – Part 1:
How are Plants Classified?
II. Classifying Plants
A. Main Idea: All plants are multicellular. Almost all make their own food using the
Sun’s energy.
Plants are classified according to the ways they transport water
and reproduce.
B.
The Plant Kingdom
1. Plants are in the domain Eukaryota.
a. They are eukaryotic life forms.
b. This means that they have nuclei in their cells.
2. Plants are multicellular.
a. Plants have differentiated tissues and organs.
b. This means they have specialized parts for certain life functions (like you
do—but plant tissues and organs are very different from yours!).
3. The cells of plants have walls.
a. Plant cells are different from animal cells in that they have these walls.
b. The cell walls are made of cellulose; it makes the walls stiff (and hard to
digest when eaten).
4. The cells of plants have chloroplasts, which are the specific structures in a plant
cell that allows them to use the Sun’s energy to make their own food in the
process known as photosynthesis.
Name: ___________________________________________________________________________________________
a. Recall that several other life forms that are not plants—or even in the same
domain as plants—also can perform photosynthesis.
b. Some examples of life forms that are not plants that can also perform
photosynthesis include (certain bacteria or archaea, for example).
5. Many plants live on dry land and do not need to be submerged in water like
certain other photosynthesizing life (such as algae).
6. The Plant kingdom can be divided into two main categories:
a. Bryophytes / Nonvascular Plants
1) These plants must soak up water without the use of roots.
a) Instead of roots, bryophytes have rhizoids.
b) Unlike the roots in plants, rhizoids do not absorb water or nutrients.
c) Their main function is to attach the plant to its substrate.
2) They need to be in a damp environment or close to a body of water.
3) Bryophytes reproduce by producing special structures call sporophytes; the
spores are usually eventually dispersed by water.
4) Examples of bryophytes include:
a) Mosses
1) Mosses have an erect shoot bearing tiny leaflike structures arranged
in spirals.
2) These are small, fairly simple, plants usually found in moist locations.
moss will cover moist, shady ground other substrates
moss usually is comprised of tiny, spiraled leaves
Name: ___________________________________________________________________________________________
b) Liverworts
1) Liverworts have a thin, leathery body that grows flat on moist soil.
2) In some cases, liverworts will grow on the surface of still water.
3) In appearance they can look leaf-like (leafy liverworts) or form large
flat sheets (thallose liverworts).
a) Thallose liverworts are quite distinctive and are easily recognized.
b) The leafy ones are easily mistaken for mosses; it can take careful
examination to tell the difference.
The photo (courtesy of William C. Steere and AIBS Bulletin) is of a
common liverwort, Ricciocarpus natans.
A liverwort thallus.
c) Hornworts
1) Hornworts have a roseate or ribbon-like body, or thallus.
2) They differ from liverworts in that they produce stem-like, hornshaped structures that grow upwards from the thallus which will
eventually split at the ends to release spores.
Hornworts grow flat across a substrate but eventually produce stalk-like extensions for the purpose of producing
and spreading spores into the environment.
Name: ___________________________________________________________________________________________
b. Tracheophytes / Vascular Plants
1) These plants have a specialized system of tube-like tissues that can
transport water, and often other (food) substances, around the tree as
needed.
2) Roots are a feature of these kinds of plants.
3) A vascular system provides support and allows some of these types of
plants to grow very tall.
4) Most plants are vascular.
5) Tracheophytes can further be divided into two subcategories:
a) Seedless plants (spore-bearing)
b) Seed plants
C. Ferns
1. Ferns are vascular plants.
a. Ferns have the following physical features:
1) Fronds (like leaves)
2) Rhizomes (like stems)
3) Roots
4) Sporangia (reproductive structure, usually found under the fronds)
2. Ferns do not make seeds, unlike most vascular plants.
3. Instead, similar to fungi, they use spores to reproduce.
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D. Gymnosperms
1. Gymnosperms are vascular plants.
2. They generate seeds.
a. Seeds contain plant embryos (the beginning of a new plant), and provide
protection and a source of food for that embryonic plant.
b. The seeds of gymnosperms are often described as “naked seeds” because
they lack the protective ovary, or fruit, generated by angiosperms.
c. The seeds are usually found in structures called cones, but sometimes they
end up within hard “berries.”
3. These plants do not create flowers or fruit.
4. Gymnosperms all produce strobili (“stro-bye-lie” – singular is strobilus
“stro-bye-luss”) for reproduction.
a. Strobili are what most people call “cones”—think pine cones here.
b. Some strobili are very different from others, though; some are not as woody
as pine cones and can be smaller, much more soft and flexible structures.
5. Gymnosperms are divided into 4 main groups:
Conifers, Cycads, Ginkgos, & Gnetophytes
a. Conifers
1) Conifers are called this because they very obviously generate cones.
2) A great example of a conifer is a pine tree, known for generating
pine cones (“male” and “female” cones are produced
by the same plant).
a) A mature female pine cone is woody; early on, they are scaly, green
and far less brittle.
b) Eventually, the scales turn woody, separate, and the seeds drop off
the scales.
c) It takes two years for a cone to develop to maturity; you often can find
pine cones of different stages of development on the same tree.
Name: ___________________________________________________________________________________________
Male strobili (cones) just before pollen release.
Female strobili (cones) of pine: The one on the left
(which would be green) is a young cone a year
after pollination, the right a mature cone that has
opened and released the seeds.
d) Pine trees and similar plants are evergreen, meaning their leaves stay
on and green all year round.
e) Trees like this have needle-like leaves.
f) They are an important resource; paper and related products are often
made from this type of tree.
g) Conifers cover a huge portion of the northern hemisphere across
several continents.
3) Some of the oldest and largest living things on Earth are conifers.
a) A single Norway spruce found in Sweden is the oldest known living thing.
1) The visible portion of this 13-foot-tall "Christmas tree" isn’t actually that
ancient (maybe 600 years)—the above ground trunks get old and die,
but then a clone grows in its place from the same root.
2) This tree’s root system has been radiocarbon dated as having been
growing for the last 9,550 years!
b) Bristlecone pines in the western United States are generally recognized as
the world's oldest continuously standing trees, though, living for about
5,000 years.
c) The largest trees are the giant sequoias (Sequoiadendron giganteum) of the
Sierra Nevada Mountains of California, reaching heights of more than 312
feet and weights of at least 4.4 million pounds (compared with 418,878
pounds for the largest recorded blue whale—but recall that the largest living
thing is actually a fungus in Oregon that is over 3 miles across).
Name: ___________________________________________________________________________________________
b. Cycads
1) Cycads are an ancient group of seed plants with a crown of large,
compound leaves and a thick trunk.
2) Cycads look a lot like palm trees.
3) Unlike palm trees, cycad also produce cones like all gymnosperms.
4) Today, only a handful of cycads still exist.
a) Many are facing possible extinction in the wild.
b) However, because of their large attractive leaves, many cycads have
found homes in public and private gardens around the world.
Typical cycad.
Cycad cones.
Material in this outline modified from material found at: http://www.ucmp.berkeley.edu/plants/anthocerotophyta.html,
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/M/Mosses.html, http://hiddenforest.co.nz/bryophytes/liverworts/intro.htm,
http://www.bio.miami.edu/dana/dox/altgen_homology.html, http://www.ohio.edu/people/braselto/readings/gymnosperms.html,
http://news.nationalgeographic.com/news/2008/04/080414-oldest-tree.html, http://www.kew.org/science-conservation/plants-fungi/ginkgo-biloba,
http://www.lithops.net/welwitschia_mirabilis_detail.htm, http://www.lithops.net/welwitschia_mirabilis_detail.htm
Name: ___________________________________________________________________________________________
c. The Ginkgo biloba tree (“gin-ko bye-loba”)
1) There is only one species of Ginkgo tree still living today, the
Ginkgo biloba, or maidenhair tree.
2) Ginkgo trees are large trees, normally reaching a height of 66–115 ft.; some
specimens in China are over 160 ft.
3) The deeply fissured, brown bark may appear cork-like in older trees.
4) Its greenish-yellow leaves are fan-shaped and composed of two or more
distinct lobes; the Latin species name biloba refers to this fact.
5) The common name of maidenhair tree pertains to the similarity of the
leaves to those of maidenhair ferns (Adiantum species).
6) This plant is deciduous; in autumn, the leaves of Ginkgo biloba turn a
golden color many find to be rather pretty before falling to the ground.
7) It takes 20-35 years for Ginkgo trees to reach maturity and start bearing seeds!
a) Male and female trees are separate plants.
1) Male trees have pollen-producing strobili.
2) Female trees, once fertilized, bear rounded, yellowish seeds with a
fleshy outer coat resembling a plum.
b) These seeds fall to the ground in the autumn.
c) As the seed coat decays it exudes a rancid smell.
8) The Ginkgo is a very hardy species, often planted in inner city areas
because it has no problem with smog or other types of pollution.
A large Ginkgo tree.
The distinctive bi-lobed leaves of the Ginkgo.
Name: ___________________________________________________________________________________________
d. Gnetophytes
1) There are three living kinds of gnetophytes:
Ephedra, Gnetum, and Welwitschia
a) Most species of Ephedra are branched shrubs (or rarely small trees)
while others are vine-like.
b) Most of the Gnetum are woody vines that climb high into trees of
tropical rain forests in central Africa, Asia, northern South America,
and islands between Australia and Asia, though some species are trees
that can grow to be about 25 ft. tall.
2) The most unusual and geographically restricted gnetophyte is
Welwitschia mirabilis, which is unlike any other plant in the world.
a) This plant was named after Friedrich Welwitsch, an Austrian naturalist
who explored Africa in the 1800's.
b) It is native to a strip of land only 50 miles wide and over 500 miles in
length along the coast of the Namib Desert, which gets less than one
inch of rainfall per year but also gets a regular fog, adding maybe
another two inches of precipitation.
c) These plants are slow growing and can live from 1500 to 2000 years.
d) They form male and female cones on separate plants.
e) They produce only two true leaves in their lifetime, and those leaves
continually grow from the base—all the while, weathering, drying out
and dying off at the tips.
f) There is a taproot that may extend downward deeply before it divides
into numerous thin roots, which must tap a supply of water not
available to other plants of the desert.
Far left: Welwitschia
next to a man for
size comparison.
Top right: Male
Welsitschia cones.
Bottom right:
Female Welwitschia
cones.