There are many similarities and differences between species within our diverse ecosystem. There are many different types of plants and animals, some more similar than others. Not surprisingly, these similarities also highlight a great deal of differences between kingdoms and even species. Analyzing these species and their differences and similarities helps us understand our incredibly diverse ecosystem. Plants make up much of life on Earth. There are four main groups of plants; bryophytes, ferns, gymnosperms and angiosperms. The most notable differences between these plants are their appearance. Bryophytes include mosses, liverworts, and hornworts. All bryophytes are small, without vascular tissue, true leaves and roots. Ferns include true ferns, club mosses, whip ferns, and horsetails. Ferns have vascular tissue, but are seedless. They are significantly larger than bryophytes, but are smaller than gymnosperms and angiosperms. Ferns, unlike bryophytes, have leaves, like angiosperms and gymnosperms. Another feature that ferns share with gymnosperms and angiosperms is vascular tissues. Gymnosperms have four main groups; conifers, ginkgo, gnetophytes and cycads. These plants get quite large. Gymnosperms have cones as one of their unique identifying factors. Gymnosperms are also unique in their leaf type, which can vary greatly from species to species. Angiosperms, being the most common plant, have a distinct appearance. Where bryophytes and ferns are short and generally small, gymnosperms and angiosperms are both large in comparison. The biggest difference between gymnosperms and angiosperms is that angiosperms produce fruits and flowers, gymnosperms...... middle of paper... other factors. For example, if bilaterally symmetrical animals have a body cavity that has formed completely within the mesoderm, also known as a coelom, it may be filed in a separate category than an individual who does not have a coelom. A digestive tract can also cause 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 paths. Direct development has no larval stage. Indirect development has a larval stage and usually undergoes metamorphosis to become mature adults.