The study of plants is called botany or plant biology. Biologists believe that the plants that live on the land today are descendants of tiny green plants that lived about 350 million years ago in the ancient seas.

Plants are divided into two major groups: the nonvascular (Bryophytes and Thallophytes) and the vascular plants (Tracheophytes). They are divided by their characteristics which are listed below.

THALLOPHYTES (algae, diatoms, kelp, seaweed)

1. small to medium (one cell--microns to meters in length)
2. aquatic (marine or fresh water)
3. found in cold to warm water, upper 200 meters of water
   

BRYOPHYTES (liverworts, hornworts, mosses, and "whiskferns")

1. small in size
2. live in the arctic and antarctic, mainly found living in the tropical and temperate areas of the world
3. need shade and moisture to survive
4. not well adapted to land conditions, have such small anchoring structures that their plant body size must remain small in order to stay clinging to surfaces

TRACHEOPHYTES (horsetails, ferns, conifers, and flowering plants)

1. large in size compared to Bryophytes
2. live where extreme cold and heat does not exist
3. need direct sunlight to survive
4. all have a long root system
5. all produce seeds

Plants which produce seeds are the plants which dominate the land today. Aquatic plants do not produce seeds. The first seed plants appeared during the Devonian period (approximately 350 million years ago) and were known as the seed ferns. Biologists believe that the seed ferns are the ancestors of the seed plants living today. The two most abundant plant groups of the Tracheophytes are the gymnosperms and angiosperms. Gymnosperms produce naked seeds and angiosperms produce seeds within flowers, fruits, or vegetables. Students should look at the worksheet and try to determine whether the plants are thallophytes, bryophytes or tracheophytes.

 PROCEDURE:

1. Students need to examine the different types of plants and then classify them into Tracheophytes, Thallophytes, or Bryophytes The answers to the worksheet are the following: - Tracheophytes (1,3,4,6,9,10); Thallophytes (2,8) ; Bryophytes (5,7)
     
2. If you have internet access have the students look up different plants and have them group them into the 3 groups.

 http://plants.usda.gov/
The PLANTS Database provides standardized information about plants, and it focuses primarily on plants of the USA and its territories, including checklists, distributional data, references and other plant information.