Although the gametes have only one set of chromosomes, that set is a shuffled mixture of genetic material from both parents. Every single egg or sperm may have a different selection of alleles from the parental chromosomes.
As with shuffling a deck of cards, many different combinations of genes can be produced without a change (mutation) in any individual gene. However, mutations do occur, and they may add alleles which were not in the population before. At any rate, the shuffling increases the variety of the offspring, and the variety gives at least some of the offspring a better chance of surviving in difficult times. The shuffling of alleles which takes place in meiosis may be the reason why sexual reproduction exists at all.
Several quite large taxa (groups of organisms) use cyclical parthenogenesis. This is when several generations are born by virgin birth, and then a generation occurs with normal sexual reproduction. Examples include aphids, and cladocerans (small crustacea called "water fleas"). Aphids usually operate as follows: when the weather is good, and their plant hosts are at their best, they use parthenogenesis. At the end of the season, when the weather gets worse, they use sexual reproduction. This system of reproduction is called "apogamy".
In parthenogenesis, the eggs contain only the mother's genetic material, and they are not fertilized. The egg cells may be produced either by meiosis or mitosis. When meiosis occurs, crossing-over produces a genetic fingerprint which differs somewhat from the mother's. So, the parthenogenetic greenfly offspring are not identical, and do show some genetic variation: some chromosome segments differ because of meiosis. Mitosis would produce identical offspring.
Amongst these parthenogenetic taxa are a number of species which have entirely abandoned sex.
A few eukaryote organisms have completely lost the ability for sexual reproduction, and so do not have meiosis. These include the Bdelloid rotifers, which only reproduce by parthenogenesis.
Meiosis can be divided into meiosis I and meiosis II.
The function of the first division is to permit crossing over. Just like mitosis, meiosis includes prophase, metaphase, anaphase and telophase.
The two cells prepare to divide again in a stage known as interkinesis or interphase II. Both of these cells will go through meiosis II.
In males, all four cells become sperm. In females, only one becomes a mature egg, while the remaining three become re-absorbed into the body.
In humans, there are certain conditions that are caused by meiosis gone wrong. Examples are:
Porsche
Dr.-Ing. h.c. F. Porsche AG, usually shortened to Porsche AG (), is a German sports car manufacturer based in Zuffenhausen. Porsche was created in 1931 as a design engineering department by Ferdinand Porsche.
Gainsharing
Gainsharing is a system of management used by a business to increase profitability by motivating employees to improve their performance through involvement and participation. As their performance improves, employees share financially in the gain (improvement). Gainsharing’s goal is to improve performance and eliminate waste (time, energy, and materials) by motivating employees to work smarter as a team rather than just working harder.
Gainsharing should not be confused with profit sharing. There are many differences between Gainsharing and profit sharing. Gainsharing is also called Gain sharing, Gainshare, and Gain share. It could also be called "savings sharing." In other words, a company shares with employees the savings from improved performance.
There are two important parts of a Gainsharing system. One is a bonus calculation. The second is a structured system for employee involvement. Because of these two parts, Gainsharing is best seen as an "organizational development" tool. It is not just a bonus or "incentive plan." In order to get a better understanding of this concept one needs to look back at Gainsharing's history.
One of the first Gainsharing plans dates back to the 1930s. In the 1930s a labor leader and MIT Lecturer Joe Scanlon, preached that “the worker” had much more to offer than just a "pair of hands" (manual labor). Scanlon believed that the person closest to the problem often has the best and simplest solution. Also, if the worker is involved in the solution he will make the solution work.
In an effort to help a troubled company, Scanlon and the company owner asked employees for their ideas and suggestions to help reduce waste and lower cost. Many improvements were made. The company became more successful. Joe was asked to save other companies who had barely survived the depression. He eventually became the Acting Director of the Steelworkers Research Department and used his skills in creating joint labor/management improvement committees to help the war effort for WWII.
After the war Joe became a lecturer at MIT and went on to develop a system for organizational development and gainsharing that became known as the Scanlon Plan.
As the Scanlon Plan developed a method to measure (calculate) gains (improvements) was created. The monetary gains were then shared with all employees. This calculation represents the bonus (monetary incentive) element of Gainsharing. This concept addresses the principle of equity. "It is fair to share." Everyone in a company makes a contribution to the organization's success. Why limit bonuses to the select few? People typically take pride in their work and have a strong desire to be respected for what they do. By sharing the company is communicating an important message to the work force: "We all contribute. That contribution is respected. Let's share in the financial benefits."
Today, companies use Gainsharing to both measure performance and reward employees when it improves. Companies use a pre-determined calculation (formula) to share the savings with all employees. The goals of a company’s Gainsharing plan depend on its cost structure and long-term competitive strategy and are tailored to fit the industry (manufacturing, service, or corporate). Information regarding the measures, formula, and gains (savings) is regularly and openly shared with all employees. Since the monetary gains are shared with employees, people develop more of a sense of ownership for their work and the company. People have a better understanding of how they influence the company's success.
It should be noted that in a Gainsharing plan, the company's current performance is compared to its historic performance (baseline period). The savings above the baseline period determine the gain or loss. This is a very important point. Since gains are measured in relationship to a historical period, employees and the company must improve in order to make a gain. Performance thresholds must be corrected periodically for the effects of capital investment in new equipment as well as for the continuous improvement needed to meet ever higher customer demands.
When people do their work differently they must change. However, as everyone one knows, it is difficult for people to change. On the other hand, do people like money? Most people would say, "Yes." Therefore, Gainsharing can be a very powerful tool. Gainsharing promotes the need for continuous improvement and eliminates employees' sense of entitlement.
A very important part of a successful Gainsharing plan is the employee involvement element of Gainsharing. In order to foster a culture of positive change, a successful Gainsharing plan needs to incorporate a structure system of employee involvement. It is common for Gainsharing plans to have a "team-based" suggestion system in place.