Biology - Plant Diversity Essay Example | Topics and Well Written Essays - 1000 words

Biology - Plant Diversity - Essay Example The most important of all radiations for land plants occurred in the early Devonian period. This was when the first rhyniophytes appeared in the fossil record and made this fossil discovery very important for paleobotany. They had some distinguishing features such as their reproductive structures which contributed to their success. Some important species that dominated their eco-system included anthropods and sporopytes and gametophytes. 2. Describe and discuss the third land flora (the â€Å"Gymnosperm Flora†) that evolved on Earth. Your answer should include the following: †¢ references to geologic time of origin and/or decline, †¢ factors that may have influenced its distribution, success and/or decline, †¢ names and brief descriptions of the most important plants that dominated this flora. Gymnosperm flora Gymnosperms are known as primitive seed plants. Their evolutionary history is long. Gymnosperms appeared in the Paleozoic and then soon became the most do minant plants world over in the Mesozoic and Caenozoic periods. They were also seen in the Tertiary Period, survived the Glacial period and have multiplied till date. While gymnosperms are only 0.36% of angiosperms, they are seen in vast areas in coniferous forests and are widely distributed world over. They are found in great abundance in China in particular. Their leaves are needlelike and evergreen. They can produce cones. A very important feature of gymnosperms is that their female sex germs reside in the ovules as in regular flowers. However the ovules are not enclosed inside the flower’s ovaries as is found in most flowering plants. It should be noted though that gymnosperms don’t produce fruits. In the biological terms, fruits are produced from maturing flower ovaries where the seeds develop in the ovules inside the ovaries. They are found in vast quantities in coniferous forests which have straight tree trunks and high timber yield of gymnosperm plants. Thuja s utchuenensis, an important specie of gymnosperm is extinct. Cycas revoluta, C. taiwaniana and C. szechuanensis, three other species of the plant are now the only cultivated plants. Some other species are as following: Cycas multipinnata, Keteleeria pubescens, K. oblonga, K. hainanensis, Abies beshanzuensis, A. yuanbaoshanensis, Picea likiangensis var. montigena, P. neoveitchii, Larix chinensis, Pseudotsuga brevifolia, Pinus squamata, Cephalotaxus lanceolata, Amentotaxus formosana and A. yunnanensis. (Cummings) Most of the aforementioned species are critically endangered and nowhere to be found today. 3. Describe and discuss the fourth land flora (the â€Å"Angiosperm Flora†) that evolved on Earth. Your answer should include the following: †¢ references to geologic time of origin, †¢ factors that may have influenced its distribution and success, (Hint: pollination and seed dispersal mechanisms, including convolution of the animal groups often involved in these mechan isms, should be a prominent feature of your answer.) †¢ Names and brief descriptions of some of the most important types of plants that dominate this flora. The evolution of angiosperms is a matter of great mystery to date. There are a lot of issues concerning their evolution today. There are speculations regarding their time of origin, the