Plant Types

"A critical step in the evolution of current plant species was the evolution of vascular tissue. Like humans have vascular tissue that transports blood through our bodies, the majority of species of plants have vascular tissue that transports water and nutrients around their bodies. Before plants evolved vascular tissue, water was only able to enter into a plant by diffusing through the plant’s cells. This meant plants were unable to grow very large because diffusion is not efficient enough to support large plants. Once plants evolved vascular tissue, they were able to grow much larger and which allowed the evolution of the giant trees that now grace the Earth’s lands. There are still many species on non-vascular plants but the vast majority of plant species contain vascular tissue. Non-vascular plants include organisms such as mosses and liverworts. Some biologists also consider the green algae to be non-vascular plants. Because non-vascular plants rely on diffusion to absorb water they are typically found in moist environments. Bark - Introduction to plantsVascular plants make up over 90% of all plant species that are currently found on Earth. More primitive vascular plants include lycophytes and ferns. These two groups reproduce with spores rather than seeds and are unable to produce wood. Gymnosperms and angiosperms are the two most recently evolved groups of vascular plants. They can both produce wood and reproduce with seeds rather than spores. Plant body plan Plants have a relatively simple body plan. A plant can be split into two sections: the underground system known as roots and the above ground system referred to as shoots. The shoots typically include stems, branches and leaves. The evolution of roots was key to the success of plants on land. Roots grow underground in search for water and nutrients in the soil. Often almost half of a plant’s mass is hidden underground in the root system. Roots also help to anchor a plant to the ground so it doesn’t get blown away in the wind or in a flood. They can also be used to store excess food to be used at a later date."