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 elcome
to Kingdom Plantae! The world of plants is exciting and definitely
ALIVE! But what is the origin of plants? Why are there so many varieties?
Although these questions are addressed in this web page, these are questions that you will eventually have to answer for yourself. As the majority of the material contained within this web page is presented from an evolutionist's point of view, the Web Mistresses of this page, would like to stress the point that evolution is only a THEORY (meaning that there is no concrete proof that it is actually true). Therefore, to get a more rounded view of this topic, we highly recommend that you study the creationist perspective as well, and then decide for yourself! In the meantime, for your learning pleasure, we present to you: Kingdom Plantae. |
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After completing this section, students should be able to:
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Plants are multi-cellular , photosynthetic organisms that became fully
adapted to land around 500 million years ago. The plants gained several
advantages from this transition: they were better able to obtain light
and carbon dioxide and there were no competing organisms on land.
However, the plants were at a disadvantage when it came to obtaining water.
To solve the problem, plants evolved by specializing some cells to perform
specific functions. The specialized cells allowed for
the potential of plants to evolve into larger organisms, but
with this new potential came new demands. The larger plants
needed more food, water, and materials to be moved into and out of
each individual cell. To accommodate the larger structure, the plants
needed more support. Woody plants then evolved from this need.
And so began the evolution of the plant . Plants have continued to adapt to their ever-changing environment over the last 300 million years and are even continuing to change today. These adaptations have helped the plants to both survive and thrive . |
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After completing this section, students should be able to:
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After completing this section, students should be able to:
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After completing this section, students should be able to name the divisions of plants. |
| Plants
are categorized into ten separate divisions (see chart).
Several methods were used to classify plants into divisions.
One of the more popular ways was for scientists to classify them according to their evolutionary history - if the plants evolved from a single common ancestor, they were often placed together on the classification chart. However, this method of classification was not the only one used. Vascular plants for instance, were often grouped according to whether they were gymnosperms or angiosperms - not by their evolutionary history. |
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Note how plants have "Divisions" instead of "phylums". |
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After completing this section, students should be able to:
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The
division bryophyta includes liverworts, hornworts, and mosses. These
plants are simple in structure, lack true roots and root systems, are held
securely to the underlying surface by rhizoids, and also lack any kind
of specialized tissues to transport water. Also, their structure is specifically
designed for food storage and support. As a result of their lack
of specialized tissue, theirmethod of collecting water differs from the
rest of the divisions'. Bryophytes must absorb water through
above ground structures; they can absorb moisture directly from the air
or by cell diffusion. Because of the difficulties that they have
in obtaining water, the majority of the bryophyte population lives in the
tropics, the bogs, and in the moist, shady places where they can easily
absorb moisture. However, some bryophytes are able to grow in temperate
regions and even in the Arctic. Like all plants, bryophytes go through
the alternation of generations life cycle.
(above) A photo of a bryophyte
The life cycle of moss begins where the parent life cycle ends, when the
mature sporophyte releases its spores from a capsule. The spore lands on
the ground, and if conditions are favorable, it germinates, forming a branched,
filamentous protonema; from this, a leafy gametophyte is formed along with
rhizoids which will secure the structure to the ground. The gametophyte
matures to produce the Antheridium, which contains the developing sperm
cells. Upon maturation, the sperm cells are released and are immediately
attracted to the archegonium. Once there, only one sperm cell will
fuse with the egg to form a zygote. Through mitosis, the zygote divides
and a sporophyte begins to develop within the archegonium.
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After completing this section, students should be able to:
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| One of the earliest known vascular plants was Rynia major. Although in appearance it was simplistic compared to the bryophytes, it did contain some very important evolutionary developments - its stem contained the first specialized tissues designed specifically to conduct water and nutrients. From the Rhynia major, it was then possible to track other important evolutionary developments. First, came the root, which not only allowed the plant to obtain water from the ground for the first time, but it also secured the plant to the ground better than rhizoids could. Next, plants developed actual leaves which were specially designed for photosynthesis to take place – plants no longer had to absorb nutrients through the rain water that fell on them. They could now officially live the life of an autotroph. The leaf itself diverged into the microphyll (this is a leaf which only has one strand of vascular tissue), and the megaphyll (this ia a leaf which contains a highly developed network of veins). However, perhaps the most important evolutionary development, is that of the xylem - a complex network of specialized vascular tissue designed to transport water throughout the plant, and phloem – a complex network of specialized vascular tissue designed to transport nutrients produced by the photosynthetic processes to the non- photosynthetic regions of the plant. Tracheids - elongated and thick walled cells, which help to support and conduct water- and vessel members - dead cells laid end to end that create a tube like conductor to help transport water and nutrients - are found inside the xylem of angiosperms. Sieve cells ( long, slender cells that carry the nutrients produced by photosynthesis), and sieve tubes ( a series of cells that transport sugar), are both found in the phloem of angiosperms. Another important development in the plant world, is that of gametophytes becoming smaller – in the case of vascular plants, the gametophyte is actually smaller than the sporophyte. Now in angiosperms and gymnosperms, the gametophyte is not only microscopic, but it is also no longer able to produce its own food. The final major evolution to take place was that of the plant's reproductive cycle becoming heterosporic, meaning that it was able to produce both male (properly called antheridia) and female (properly called archegonia) sporangium. |
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After completing this section, students should be able to:
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There are four divisions of seedless vascular plants. They are:
Psilophyta (whisk ferns), Lycophyta
(club mosses), Sphenophyta
(horsetails), and Pterophyta (ferns).
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Three images on this web page were taken from the book 5th Edition Biology by Helen Curtis & N. Sue Barnes Published by WORTH PUBLISHERS, INC. Copy Right 1968,1979,1983, and 1989 Image #1 is of the Lilly Pads, and appears under Section 4; The Diversity of Life, Chapter 24; The Plants, on page 493. (Image 24-1) It should be noted that this image does not appear exactly as it does in the book. The book credits the image to James L. Castner. On a Personal note, Mr. Castner, if there is a problem with us using your photo, please contact the Allegany County Board of Education, and they will notify us to remove it. Image #2 is of a chart on the Classification of Living plants, and appears under Section 4; The Diversity of Life, Chapter 24; The Plants, on page 498. (Table 24-2) The book credited the chart to L.E. Graham and K.J. Nicklas. Once again, if there is a problem with our using you image, Please contact the Allegany County Board of Education. Image #3 is of the Moss life Cycle, and appears under Section 4; The Diversity of Life, Chapter 24; The Plants, on page 500. (Image 24-8) Sorry, the book did not credit the person who created this image. - You know who you are, Thanks!!!!! Other
Credits
5th Edition Biology by Helen
Curtis & N. Sue Barnes
All other photos
on this site were taken from web sites which allow the use of their photos
for educational purposes. If by chance we have made a mistake, and used
any images with out permission, promptly contact the Allegany
County Board of Education. They will alert us to our error immediately.
Allegany County Board of
Education
Email: www.boe.allconet.org |
