An ecosystem is a community of living organisms in conjunction with the nonliving components of their environment, interacting as a system. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy is incorporated into plant tissue. By feeding on plants and on one-another, animals play an important role in the movement of matter and energy through the system, they influence the quantity of plant and microbial biomass present. By breaking down dead organic matter, decomposers release carbon back to the atmosphere and facilitate nutrient cycling by converting nutrients stored in dead biomass back to a form that can be used by plants and other microbes. Ecosystems are controlled by internal factors. External factors such as climate, parent material which forms the soil and topography, control the overall structure of an ecosystem but are not themselves influenced by the ecosystem. Unlike external factors, internal factors are controlled, for example, root competition, disturbance and the types of species present.

Ecosystems are dynamic entities—they are subject to periodic disturbances and are in the process of recovering from some past disturbance. Ecosystems in similar environments that are located in different parts of the world can end up doing things differently because they have different pools of species present. Internal factors not only control ecosystem processes but are controlled by them and are subject to feedback loops. Resource inputs are controlled by external processes like climate and parent material. Resource availability within the ecosystem is controlled by internal factors like decomposition, root competition or shading. Although humans operate within ecosystems, their cumulative effects are large enough to influence external factors like climate. Biodiversity affects ecosystem functioning, as do the processes of disturbance and succession. Ecosystems provide a variety of services upon which people depend; the term ecosystem was first used in 1935 in a publication by British ecologist Arthur Tansley.

Tansley devised the concept to draw attention to the importance of transfers of materials between organisms and their environment. He refined the term, describing it as "The whole system... including not only the organism-complex, but the whole complex of physical factors forming what we call the environment". Tansley regarded ecosystems not as natural units, but as "mental isolates". Tansley defined the spatial extent of ecosystems using the term ecotope. G. Evelyn Hutchinson, a limnologist, a contemporary of Tansley's, combined Charles Elton's ideas about trophic ecology with those of Russian geochemist Vladimir Vernadsky; as a result, he suggested. This would, in turn, limit the abundance of animals. Raymond Lindeman took these ideas further to suggest that the flow of energy through a lake was the primary driver of the ecosystem. Hutchinson's students, brothers Howard T. Odum and Eugene P. Odum, further developed a "systems approach" to the study of ecosystems; this allowed them to study the flow of material through ecological systems.

Ecosystems are controlled both by internal factors. External factors called state factors, control the overall structure of an ecosystem and the way things work within it, but are not themselves influenced by the ecosystem; the most important of these is climate. Climate determines the biome. Rainfall patterns and seasonal temperatures influence photosynthesis and thereby determine the amount of water and energy available to the ecosystem. Parent material determines the nature of the soil in an ecosystem, influences the supply of mineral nutrients. Topography controls ecosystem processes by affecting things like microclimate, soil development and the movement of water through a system. For example, ecosystems can be quite different if situated in a small depression on the landscape, versus one present on an adjacent steep hillside. Other external factors that play an important role in ecosystem functioning include time and potential biota; the set of organisms that can be present in an area can significantly affect ecosystems.

Ecosystems in similar environments that are located in different parts of the world can end up doing things differently because they have different pools of species present. The introduction of non-native species can cause substantial shifts in ecosystem function. Unlike external factors, internal factors in ecosystems not only control ecosystem processes but are controlled by them, they are subject to feedback loops. While the resource inputs are controlled by external processes like climate and parent material, the availability of these resources within the ecosystem is controlled by internal factors like decomposition, root competition or shading. Other factors like disturbance, succession or the types of species present are internal factors. Primary production is the production of organic matter from inorganic carbon sources; this occurs through photosynthesis. The energy incorporated through this process supports life on earth, while the carbon makes up much of the organic matter in living and dead biomass, soil carbon and fossil fuels.

It drives the carbon cycle, which influences global climate via the greenhouse effect. Through the process of photosynthesis, plants capture energy from light and use it to combine carbon dioxide and water to produce carbohydrates and oxygen; the photosynthesis carried out by all the plants in an ecosystem i

1978 Tour de France, Stage 12a to Stage 22

The 1978 Tour de France was the 65th edition of the Tour de France, one of cycling's Grand Tours. The Tour began in Leiden, the Netherlands, with a prologue individual time trial on 29 June, Stage 12a occurred on 12 July with a flat stage from Tarbes; the race finished in Paris on 23 July. 12 July 1978 - Tarbes to Valence d'Agen, 158 km The stage was neutralised after a protest, by the peloton, about split stages. The peloton rode throughout the stage, came to a stop 100 m before the finish line; the riders dismounted their bikes, crossing the finish line on foot, the stage was cancelled by the race commissaires. 12 July 1978 - Valence d'Agen to Toulouse, 96 km 13 July 1978 - Figeac to Super Besse, 221 km 14 July 1978 - Besse-en-Chandesse to Puy de Dôme, 52 km 15 July 1978 - Saint-Dier-d'Auvergne to Saint-Étienne, 196 km 16 July 1978 - Saint-Étienne to Alpe d'Huez, 241 km 17 July 1978 - Alpe d'Huez 18 July 1978 - Grenoble to Morzine, 225 km 19 July 1978 - Morzine to Lausanne, 137 km 20 July 1978 - Lausanne to Belfort, 182 km 21 July 1978 - Metz to Nancy, 72 km 22 July 1978 - Epernay to Senlis, 207 km 23 July 1978 - Saint Germain en Laye to Paris Champs-Élysées, 162 km

Leg cutter

A leg cutter is a type of delivery in the sport of cricket. It is bowled by fast bowlers. A bowler releases a normal spin delivery with the wrist locked in position and the first two fingers positioned on top of the cricket ball, giving it spin about a horizontal axis perpendicular to the length of the pitch. For a leg cutter, a right-handed bowler pulls his fingers down the left side of the ball, rolling the ball out of his hand over the little finger, in an action similar to bowling a leg break, only at higher speed; this changes the axis of spin to make it more like a leg break, which makes the ball deviate to the left when it bounces on the pitch. From a right-handed batsman's point of view, this deviation is to the right, or from the leg side towards the off side; this deviation is known as cut, the delivery is called a leg cutter because it moves away from the leg side. What differentiates a genuine leg cutter from a seam-up delivery that moves away off the seam is that it is deliberately bowled.

Leg cutters do not turn as as leg breaks bowled by a leg spin bowler, but at the speed of a fast bowler a tiny deviation can cause difficulties for the batsman. If he is not quick enough to react to the movement, the batsman can edge the ball off the outside edge of his bat, offering a catch to the wicket-keeper or slips fielders. A fast bowler will use the leg cutter as a variation ball as it is most effective when it surprises the batsman; the leg cutter action can produce a slower ball with little obvious change in the bowler's arm speed, making the delivery doubly deceptive. On the other hand, the lack of pace of the delivery may be disadvantageous. Former Australian captain Ian Chappell described Jeff Thomson's leg cutter thus: "He had this leg cutter, you were pretty happy to see it, because it meant that the ball wasn't coming at your head at 95 miles an hour." The most prominent users of leg cutter include Alec Bedser, Fazal Mahmood and of late Terry Alderman, Carl Rackemann and Venkatesh Prasad.

Leg cutters are much more seen in indoor cricket as the physical arena in which the game is played limits the pace at which bowlers can bowl, hence they must use other techniques to prevent the batsmen from scoring. Off cutter