Angiosperms
Angiosperms, also called flowering plants, produce flowers and fruits. There are approximately 25,000 known existing species of angiosperms; they are also the most diverse and geographically widespread of all plants. These plants have cells specifically for transporting water called vessel elements. Angiosperms have a part of the plant called fiber, which supports the structure of the plant. Their seeds are contained inside of the plant. Angiosperms are heterosporous, meaning that they have two types of spores, male and female. These spores are of different sizes, the megaspore being the female spore and the microspore being the male spore. These spores develop to hold male and female gametes.
Angiosperms are found on almost every habitat on Earth, including aquatic habitats. They are even found in Antarctica. Marine angiosperms are usually found in tropical habitats, and are called "seagrasses."
The types of angiosperms are amborrel, water lilies, monocots and dicots. Amborrel are small shrubs with red fruit and little, greenish-yellow flowers, and are only located on an island in the South Pacific called New Caledonia. Amborrel are the first currently existing species that did not evolve from a known common ancestor. Water lilies live in freshwater in tropical and temperate climates; there are around 70 different species of water lilies. Monocots and dicots are named for the number of their cotyledons, or seed-bearing leaves. Some monoctos include grasses, palms, yuccas, and orchids. They contain one cotyledon, while dicots contain two. Monocots have an adventitious root system, as well as flower parts and vacular bundles in sets of three. Dicots have a netlike arrangement of veins on the leaves and a tap roots system that is made of a ring of vascular bundles and flower parts in groups of four or five. Eudicots are another kind of angiosperm, and include most dicots. These include roses, peas, sunflowers, buttercups, oaks, and maples.
Like gymnosperm, angiosperm have xylem cells known as tracheids, which distribute water and nutrients throughout the plant. They also have shoots with four circles of leaves, called sepals, petals, stamens, and carpels. Flowers specifically operate as reproductive organs. Sepals are leaves that are closed around the flower bud before it opens, and are typically green. Petals are usually of bright colors, and help the plant attract pollinators to the flower. Sporophylls produce spores, and are inside of the ring of petals. Though flowers are specialized in fertilization, the sepals and petals do not contribute to the process of fertilization. Stamens and carpels are the two rings of sporophylls, stamens being the male reproductive organs and carpels being the female reproductive organs. Stamens produce male gametes and carpels produce female gametes; the stamens produce pollen and the carpels recieve pollen. Eventually ovaries develop at the base of the carpels, with ovules held inside of the ovaries. Post fertilization, the ovules develop into seeds.
A mature ovary is known as a fruit, which help the plant disperse seeds. Depending on the plant, fruits have various anatomical structures that aid in distribution of seeds. Some, such as dandelions, have mechanisms that allow them to be carried in the wind, while others rely on animals by either attatching to the animal's fur or existing in the form of an edible fruit.
To adapt to their enironment and distance from water, angiosperms evolved to rely on insects to avert self-fertilization and allowing diverse fertilization of plants. Angiosperms have also use flowers and fruits to protect seeds and pollen, and bright colored petals to ward off predators.
Numerous different organisms rely on angiosperms as a source of food, including insects, herbivores, and omnivores. Even carnivores rely on angiosperms to provide food for their prey, so that the prey will be available for the predator to eat. This makes angiosperms imperitive to the food web and the survival of most other organisms.
