Timothy F. Coleman
Plants are currently classified as multicellular organisms composed of eukaryotic cell that are enclosed in walls of cellulose and contain chloroplasts. Plants capture energy from sunlight and convert it to nutrients that will be used by the plant and other the organisms that feed off them. Plants are the foundation of most food webs where they were they are labeled
producers
. Plants are important in our ecosystems since they absorb great quantities of carbon dioxide and release the oxygen we breathe. Plants also take up water from the soil and give up large amounts of water vapor. They provide shelter, building material, a place to lay eggs, and to bear young. They also provide humans with fuel, fertilizer, drugs, pesticides, ornamentation and research material. Plants lay the foundation of most ecosystems where they are the base layer of the biomass pyramid. The biomass pyramid is a measure of all the mass in an ecosystem sorted and accumulated by its role. Roles are defined as producers (the organisms that produce their own food energy). Primary consumers, those organisms that eat the producers also called herbivores. Secondary consumers are those organisms which eat the primary consumers. Secondary consumers are also called carnivores. The tertiary consumers are at the high point of the food chain and will consume the secondary consumer. Plants will make close to 90% of the biomass of most ecosystems.
In biology, the equivalent of a phylum in the plant or fungi kingdom is called a division.The main plant divisions, in the order in which they probably evolved, are the mosses (Division Bryophyta), the ferns (Division Filicophyta), the horsetails (Division Sphenophyta), the Cycads (Division Cycadophyta), the Ginkgo (Division Ginkgophyta), the conifers (Division Pinophyta), the gnetophytes (Division Gnetophyta), and the angiosperms (Division Anthophyta).
Since the purpose of this exercise is to give a high level overview of the identification of the organisms in the neighborhood, the student be able to identify the more common species in our local area with field guides.. Once a plant is identified they can see where a plant falls in the general scheme of classification. They should begin to see the taxonomic trends that exist between the species. AP students need to pay particular attention to the life cycles of each of the major phyla and evolutionary trends.
The mosses are nonvasculated plants that can live in either shady or sunny spots. Often they are found in swamps or bogs. Mosses lack true roots and without a vascular system they are limited in size. They can also be found on bare ground or rocky crevices as pioneer plants where they break down the rock into soil providing a jump point for other plants to begin their colonization in a location that was once barren to them.
Horsetails have only a few dozen species of which 8 grow in Connecticut. These plants are the earliest type of plant with a defined vascular system. Earlier they flourished in swamps of the Carboniferous Period with some species growing the size of a full tree. In Connecticut the few examples of the horsetails are club mosses and spike mosses. They tend to grow in the matted forest floors.
Ferns are another example of an early vascular plant. Vascular tissues allow the movement of water and nutrients far greater distances than by osmotic differences alone. This allows a plant to grow to greater heights than their nonvasculated competitors. They are easily recognized because of the Christmas tree pattern of their fronds. Like the horsetails they were dominant in the Carboniferous Period when fern trees grew to heights exceeding 40 feet.
Conifers are our "evergreens". They are recognized by their needle like leaves that are not shed during the winter. They get their name from the woody cones in which the seeds are borne. Common examples in Connecticut are the white pine, spruce ,hemlock and many ornamental shrubs
Angiosperms are flowering plants that dominate the plant world (80% of all vascular plants are angiosperms). They are indeed the most successful division in terms of sheer number of species. There are a number of reasons for their success most notably the proactive nature of seed production, which allows seeds to be carried to geographic locations beyond the base of the plant. Angiosperms can further be divided into a long list of classes depending upon the number of cotyledons or seed leaves that are found in the embryo. Monocots have one while dicots have two.
Some common families of the monocots include
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- Typhascae: the cattails
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- Gramineae: the grasses bamboo, and cereal grains
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- Liliacaeae; the lilies, onion and tulips
Some of the more common dicot families include
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- Salincaceae: willows, populars, and cottonwoods
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- Juglandaceae: walnuts and hickory
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- Aceraceae: maples
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- Ericaaceae: laurels rhododendrons, azalea, and heather
