BACKGROUND:
There are over 300,000 types of plants in
several large groups. There are slightly different classification systems for
plants, but most recognize two basic groups, the nonvascular plants, and the
vascular plants. The vascular plants are distinguished by conducting tissues
called xylem and phloem tissues. Xylem tissue transports water and phloem
tissue transports food products. These tissues are absent in nonvascular
plants. Nonvascular plants in the classification used in this curriculum
include brown-green algae (including diatoms), brown-red algae, mosses, and
liverworts. Vascular plants include ferns (filicopsids), sphenopsids (horse
tails), gymnosperms (pine trees), and angiosperms (flowering plants).
Nonvascular plants are sometimes referred to as thallus.
Brown-green algae refers to mainly one
celled plants called diatoms. Diatoms are a major component of the oceans.
Diatoms are important because they are at the bottom on the food chain.
Brown-red algae refers to large plants of the sea, including kelp and seaweed.
Plants in the marine environment do not need the elaborate system of getting
nutrients to all parts of their bodies, because the marine environment has all
these nutrients available. However, marine plants must develop a way to rid
themselves of salt. Bryophyta which includes mosses and liverworts are mainly
inconspicuous plants growing in moist habitats. They are not fully adapted to
life on land because they need water to reproduce. Bryophytes do not get very
large.
Sphenophyta or horsetails are easily
recognized by their jointed stems and rough, ribbed texture. Early settlers
used horsetails to help clean pots and pans because of their rough texture.
These plants are vascular and may be found in wet environments.
Ferns (filicopsids) are familiar vascular
land plants that reproduce by using spores rather than seeds. Ferns prefer
wet, moist climates.
Gymnosperms (which include Ginkgoes) or
conifers (just the pine-like trees) are mainly cone-bearing plants. There are
only about 550 species of living conifers. They dominate the forests of the
Northern Hemisphere, but are known in the tropics and Southern Hemisphere. The
leaves of most conifers are needle-shaped and are all simple. Angiosperms
(flowering plants) produce a seed cover for reproduction and are the most
common small plants and trees. They are divided into groups monocots (grasses)
and dicots (larger flowering plants).
PROCEDURE:
- Give students worksheet and go over
the different groups using the information provided above.
- You may want to go outside and see what
major groups you can find. Most of them will be angiosperms or gymnosperms.
Some ferns may be around, and if you live in a rural, wet area you may
have sphenospsids or horsetails. Emphasis with students that plants have a
more complicated division, but this is to get them to think about how we
should classify plants.
