There are many similarities and differences between species within our diverse ecosystem. There are many types of plants and animals, some more similar than others. Not surprisingly, these similarities also highlight many differences between kingdoms and even between species. Analyzing these species and their differences and similarities helps to better understand our incredibly diverse ecosystem. Plants make up a large part of life on Earth. There are four major groups of plants; bryophytes, ferns, gymnosperms and angiosperms. The most notable differences between these plants are in their appearance. Bryophytes include mosses, liverworts and hornworts. All bryophytes are small, without vascular tissue, true leaves or roots. Ferns include true ferns, club moss, whip fern, and horsetail. Ferns have vascular tissue, but are seedless. They are significantly larger than bryophytes, but smaller than gymnosperms and angiosperms. Ferns, unlike bryophytes, have leaves, just like angiosperms and gymnosperms. Vascular tissues are another trait that ferns share with gymnosperms and angiosperms. Gymnosperms include four main groups: conifers, ginkgos, gnetophytes and cycads. These plants grow quite large. Gymnosperms have cones as one of their unique identifying factors. Gymnosperms are also unique in their leaf types, which can vary greatly between species. Angiosperms, being the most common plant, have a distinct appearance. Where bryophytes and ferns are low and generally small, gymnosperms and angiosperms are both large in comparison. The biggest difference between gymnosperms and angiosperms is that while angiosperms produce fruits and flowers, gymnos... middle of paper ... other factors. For example, if bilaterally symmetric animals have a fully formed body cavity in the mesoderm, also called a coelom, it may be placed in a separate category than an individual that does not have a coelom. A digestive tract may also give rise to a different classification. For example, sponges do not have a digestive tract, other animals have an incomplete digestive tract, and still others have a complete digestive tract. If an animal has a segmented body, it may also be considered for a different classification. The last special classification factor is reproduction and development. Most animals participate in sexual reproduction. Animals can then take one of two developmental pathways. Direct development does not include a larval stage. Indirect development has a larval stage and usually undergoes metamorphosis to become mature adults..