Origins of the flower

he family Amborellaceae is regarded as being the sister clade to all other living flowering plants. The complete genome of Amborella trichopoda is still being sequenced as of March 2012. By comparing its genome with those of all other living flowering plants, it will be possible to work out the most likely characteristics of the ancestor of A. trichopoda and all other flowering plants, i.e. the ancestral flowering plant.[94] It seems that on the level of the organ, the leaf may be the ancestor of the flower, or at least some floral organs. When some crucial genes involved in flower development are mutated, clusters of leaf-like structures arise in place of flowers. Thus, sometime in history, the developmental program leading to formation of a leaf must have been altered to generate a flower. There probably also exists an overall robust framework within which the floral diversity has been generated. An example of that is a gene called LEAFY (LFY), which is involved in flower development in Arabidopsis thaliana. The homologs of this gene are found in angiosperms as diverse as tomato, snapdragon, pea, maize and even gymnosperms. Expression of Arabidopsis thaliana LFY in distant plants like poplar and citrus also results in flower-production in these plants. The LFY gene regulates the expression of some genes belonging to the MADS-box family. These genes, in turn, act as direct controllers of flower development. Cladistics (Ancient Greek: , klados, "branch") is an approach to classification in which items are grouped together based on whether or not they have one or more shared unique characteristics that come from the group's common ancestor and are not present in more distant ancestor

. Therefore, members of the same group are thought to share a common history and are considered to be more closely related.[1][2][3][4] The original method for cladistic analysis and the school of taxonomy derived from it originated in the work of the German entomologist Willi Hennig, who referred to it as "phylogenetic systematics" (also the title of his 1966 book); the use of the terms cladistics and clade was popularized by other researchers. The techniques and sometimes the names have been successfully applied in other disciplines: for example, to determine the relationships between the surviving manuscripts of the Canterbury Tales,[5] or also between 53 manuscripts of the Sanskrit Carakasa?hita Vimanasthana. The word "tomato" may refer to the plant (Solanum lycopersicum) or the edible, typically red, fruit that it bears. Having originated in America, the tomato was spread around the world following the Spanish colonization of the Americas, and its many varieties are now widely grown, often in greenhouses in cooler climates. The tomato is consumed in diverse ways, including raw, as an ingredient in many dishes and sauces, and in drinks. While it is botanically a fruit, it is considered a vegetable for culinary purposes (as well as by the United States Supreme Court, see Nix v. Hedden), which has caused some confusion. The fruit is rich in lycopene, which may have beneficial health effects. The tomato belongs to the nightshade family. The plants typically grow to 13 meters (310 ft) in height and have a weak stem that often sprawls over the ground and vines over other plants. It is a perennial in its native habitat, although often grown outdoors in temperate climates as an annual.