User:CDoris-Bio341/sandbox Choice

Article:Fruit anatomy

Choice Project Final Draft: Categories of fruits
Fruits are found in three main anatomical categories: simple fruits, aggregate fruits, and multiple fruits. Aggregate fruits are formed from a single compound flower and contain many ovaries or fruitlets. Examples include raspberries and blackberries. Multiple fruits are formed from the fused ovaries of multiple flowers or inflorescence. An example of multiple fruits are the fig, mulberry, and the pineapple. Simple fruit are formed from a single ovary and may contain one or many seeds. They can be either fleshy or dry. In fleshy fruit, during development, the pericarp and other accessory structures become the fleshy portion of the fruit. The types of fleshy fruits are berries, pomes, and drupes. In berries, the entire pericarp is fleshy but this exculdes the exocarp which acts as more as a skin. There are berries that are known as pepo, a type of berry with an inseparable rind, or hesperidium, which has a separable rind. An example of a pepo is the cucumber and a lemon would be an example of a hesperidium. The fleshy portion of the pomes is developed from the floral tube and like the berry most of the pericarp is fleshy but the endocarp is cartilaginous, an apple is an example of a pome. Lastly, drupes are known for being one seeded with a fleshy mesocarp, an example of this would be the peach. However, there are fruits were the fleshy portion is developed from tissues that are not the ovary, such as in the strawberry. The edible part of the strawberry is formed from the receptacle of the flower. Due, to this difference the strawberry is know as a false fruit or an accessory fruit. There is a shared method of seed dispersal within fleshy fruits. These fruits depend on animals to eat the fruits and disperse the seeds in order for their populations to survive. Dry fruits also develop from the ovary but unlike the fleshy fruits they do not depend on the mesocarp but the endocarp for seed dispersal. Dry fruits depend more on physical forces, like wind and water. Dry fruits' seeds can also perform pod shattering, which involve the seed being ejected from the seed coat by shattering it. Some dry fruits are able to perform wisteria, which is an extreme case where there is an explosion of the pod, resulting the seed to be dispersed over long distances. Like fleshy fruits, dry fruits can also depend on animals to spread their seeds by adhering to animal's fur and skin, this is known as epizoochory. Types of dry fruits include achenes, capsules, follicles or nuts. Dry fruits can also be separated into dehiscent and indehiscent fruits. Dry dehiscent fruits are described as a fruit where the pod has an increase in internal tension to allow seeds to be released. These include the sweet pea, soybean, alfalfa, milkweed, mustard, cabbage and poppy. Dry indehiscent fruit differ in that they do not have this mechanism and simply depend on physical forces. Examples of species indehiscent fruit are sunflower seeds, nuts, and dandelions.

Evolutionary History
There is a wide variety in the structures of fruit across the different species of plants. Evolution has selected for certain traits in plants that would increase their fitness. This diversity arose through the selection of advantageous methods for seed protection and dispersal in different environments. It is know that dry fruits were present before fleshy fruits and fleshy fruits diverged from them. A study looking at the Rubiaceae family found that within the family, fleshy fruits had evolved independently at least 12 times. This means that fleshy fruits were not passed on to following generations but that this form of fruit was selected for in different species. This may imply that fleshy fruit is a favorable and beneficial trait because not only does it disperse the seeds, but it also protects them. There is also a variety of dispersal methods that are used by different plants. The origins of these modes of dispersal have been found to be a more recent evolutionary change. Of the methods of dispersal, the plants that use animals have not changed in many ways from the original trait. Due to this, it may be assumed that animal dispersal is a efficient form of dispersal, however there has be no evidence that it increases dispersal distances. Therefore, the question remains of what evolutionary mechanism causes such dramatic diversity. It has been found, however, that simple changes within developmental regulatory genes can cause large alterations within the anatomical structure of the fruit. Even without knowing the mechanism involved in the biodiversity of fruit, it is clear that this diversity is important to the continuation of plant populations.