Essay about Biology

Negative and positive feedback processes both occurs in the enzyme pathways. The difference between positive and negative feedback is that in negative feedback, the protein being produced by the enzyme or the protein produced as a result of a chain of proteins becomes very much concentrated. Consequently, the protein then inhibits the enzyme through placing themselves at the start of the chain. The protein attachment places itself in an allotter site thereby changing the shape of the enzyme instead of changing the functional site where the protein would prevent the enzyme from including some other proteins (Werner, 1999).
In the positive feedback, instead of inhibiting the reactions, it accelerates them. Positive feedback occurs when a certain enzyme is created and this particular enzyme signals the body to continue producing lots of that enzyme. Through this signals, the enzyme becomes its own catalyst in the process. When the loop begins, it moves with an accelerating speed until a larger feedback stops it. The greatest difference between the two is that, negative feedback manages to inhibit a reaction after the creation of a lot of products while positive feedback accelerates the process which produces the product (Werner, 1999).
(b) Biological definition of a flower A flower is also referred to as bloom (blossom). This is the reproductive part located in the flowering plants. It can also be defined as a modified stem with reduced internodes and bearings. At the nodes, it has parts which may be highly modified leaves. Actually, the flower forms at the axis with an apical meristem that has its growth determinate. There are some biological means by which flowers attach themselves to the plants. The sessile flower is a term referred to those types of flowers that form at the axil of the leaf, but they do not have stems.

The penduncle is the stem that holds one flower when it is produced. Incase of groups of flowers held by the penduncle, each stem holding the different flowers is referred to as the pedicel. The flowering stem forms the receptacle (torus). This is the terminal end of the stem (Stewart, 2004). The flower parts are arranged in four main parts or whorls. These parts are arranged in whorls on the torus. Flowering plants are classified under the division Magnoliophyta also referred as Angiosperms.
Flowering plants are heterosporangiate meaning that they can produce both the female and the male reproductive spores. The male reproductive spores are referred as pollen and the female reproductive spores are called ovules. Both of these spores are produced by different organs although a typical flower (bisporangiate strobilus) contains both the organs. The flower performs the function of mediation between the male and female ovum. It allows the union of both ovums which leads to the production of seeds. The process commences with pollination and then fertilization.
This processes lead to the formation and dispersal of seeds. Each flower is specifically designed to provide for effective transfer of pollen. For the higher plants, the dispersed seeds are the next generation. They are the primary source by which species of other generation could be dispersed to many different landscapes. Inflorescence refers to the process of grouping flowers. The Crateva religiosa is a very good example of a perfect flower. It has both the outer ring referred to as the stamen and the center referred to as the pistil (Stewart, 2004).

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