Taxonomy is the science involved in classifying living organisms and it is an important part of both animal and plant biology. The current process of classifying organisms is based upon a hierarchical system that starts with very broad categories that have very general descriptions covering a wide variety of organisms. Each level below this broad category get more and more narrow and covers fewer and fewer organisms. The categories that are generally used are:
Phylum or Division
Therefore, by the time you get down to the species level there is only one organism in the entire world that will fit that exact description.
It is the last categories that an organism fits into that we use to name it scientifically. Thus, all organisms are given scientific names composed of a genus and a species such as:
Homo sapiens humans
Canis familiaris dogs
Zea mays corn
It is important to remember that, as you write these names you must always capitalize the genus but never the species. You should also either underline or italicize the words.
In looking at the taxonomy of the plant kingdom, we are going to examine only a few representative taxonomic groups. We will concentrate on the most common and, to us, most important group in more detail.
KINGDOM: A simple characterization of the plant kingdom would mention that all its members are multicellular with well developed tissues, are capable of undergoing photosynthesis and are primarily found on land. They also have chlorophyll a and b and contain cellulose in their cell walls.
DIVISIONS: In the plant and fungi kingdoms, "divisions" are use rather than "phyla". In this abbreviated study of plant taxonomy we will be looking only at only 6 divisions in this field study although others may be covered in the lab.
Division Hepatophyta: Liverworts
Division Bryophyta: Mosses
Division Pterophyta: Ferns
Division Coniferophyta: Conifers
Division Ginkophyta: Ginkos
Division Anthophyta: Flowering plants
CLASSES: While many of the divisions we will study have classes we will only study the two classes in the Division Anthophyta. The first of these classes is commonly known as the Monocots which is short for Monocotyledonae. A cotyledon is the seed leave that first supplies the growing plant with its nutrients. Since "mono" refers to "one", this group of plants has only one of these seed leaves. Examples include corn, lilies, bamboo and palm trees. If a seed has two cotyledons it is known as a Dicot and is in the class Dicotyledonae. The majority of plants we encounter everyday fall into this class. Table 1 summarizes the easily identifiable differences that exist between these two classes of plants.
TABLE 1: CHARACTERISTICS OF MONOCOTS AND DICOTS
CHARACTERISTIC MONOCOTS DICOTS
Number of cotyledons One Two
Vascular arrangement in stem Scattered Ring shaped
Root phloem arrangement Ring shaped Between xylem arms
Leaf venation Parallel pattern Net pattern
Flower structure Flower parts in 3's and multiples of 3's Flower parts in 4's or 5's and multiples of 4's and 5's
ORDERS: We will not discuss any orders involved in the plant groups we examine
FAMILIES: This level is particularly helpful in understanding relations, similarities and differences that exist between plant groups. Since families are the unit directly above the genus/species name, knowing the families allows one to easily group similar plants. This is particularly true if one is familiar with both the scientific and common family names as listed in Table 2. Again, we will concentrate only on those within the Division Anthophyta.
TABLE 2: COMMON NAMES OF RELEVANT PLANT FAMILIES
SCIENTIFIC NAME COMMON NAME SCIENTIFIC NAME COMMON NAME
Asteraceae Sunflower Myrtaceae Myrtle
Cactaceae Cactus Papaveraceae Poppy
Cupressaceae Cypress Pinaceae Pine
Ericaceae Heath Platanaceae Sycamore
Fagaceae Beech Ranunculacea Crowfoot
Hamamelidaceae Witch Hazel Rhamnaceae Buckthorn
Iridaceae Iris Rosaceae Rose
Lamiaceae Mint Saxifragaceae Saxifrage
Leguminosae Pea Scrophulariaceae Figwort
Liliaceae Lily Taxodiaceae Bald Cypress
GENUS and SPECIES: Since these are the groups used to scientifically name the organisms, it is important to be familiar with them. Again, we will examine relatively few plants at this detail and they will be selected on the basis of providing representatives from as many families and classes as possible.
MATERIALS & METHODS:
1. LOWER PLANTS: Use the campus map to locate the following plants that are not on the "Interpretive Garden Plant Lists". Find each of these and make note of the distinguishing features for the following plant parts: roots, stems, leaves, reproductive units (flowers, cones, etc.) in the tables provided in the "Results" section. If they do not appear to posses these items, note what seems to be taking their place or why they do not need them.
Non-vascular plants: These plants do not have vascular system (phloem and xylem) to conduct material long distances. They also do not produce "seeds" or "spores" which can protect the sperm and eggs from drying out. These two factors keep them very small and close to the ground. They will usually be found in very moist areas.
Division Hepatophyta: Liverworts Located in garden south of Science
Division Bryophyta: Mosses Located between Mall and east side of
Vascular, Seedless Plants: These plants have a true vascular system containing xylem and phloem but they do not have true roots. Instead they have rhizoids which function in a similar but less effective way. This allows them to grow substantially larger as long as they are still in areas where there is abundant moisture. Thus, in tropical rain forests, some ferns can be up to fifty feet tall. Since they do not produce seeds, however, they still require moisture to keep their spores from drying out when they reproduce.
Division Pterophyta: Ferns Located in garden south of Science
Vascular, Seed-producing Plants: These plants are the most "advanced" in terms of their anatomy and physiology. They have true roots, stems, and leaves. Their vascular system is complex and wide spread. Besides allowing them to conduct water and nutrients long distances they provide support that allows the plants to grow up to 400 feet tall. However, another adaptation to life on land that is unique to this group is the ability to produce seeds. These structures are multicellular organs with specialized structures to insure survival of the seed. Seed coats prevent drying out and the cotyledons provide nutrients for the growing embryo.
The seeds will be found either in cones or flowers. Cones are typically found in a group called the Gymnosperms which, while not a legitimate taxonomic category, is a term used for all plants bearing seeds in cones. Those plants in which the seeds are carried in flowers are called the Angiosperms.
For this portion of the exercise you will be using the Interpretive Garden Location Maps and the Interpretive Garden Plant Lists. Using the Plant List, locate a plant fitting the category requested and record the number alongside it. Using the maps, find that number on a plant icon and then locate the plant in the garden. Once the plant has been located, examine it and complete the chart.
Division Hepatophyta: Liverworts Plant used:
Division Bryophyta: Mosses Plant used:
Division Pterophyta: Ferns Plant used:
Pinus family Cupressaceae family Taxodiaceae family
Agavaceae family Liliaceae family Iridaceae family
family family family
Using at least one example from each of the above tables write a paragraph explaining how the taxonomic groups of plants progress in their ability to handle life on dry land.