User talk:Manisha764

An ecosystem is a community of living organisms in conjunction with the nonliving components of their environment, interacting as a system.[2] These biotic and abiotic components are linked together through nutrient cycles and energy flows.[3] Energy enters the system through photosynthesis and 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 also 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 readily used by plants and other microbes.[4]

Ecosystems are controlled by external and 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.[5] Unlike external factors, internal factors are controlled, for example, decomposition, root competition, shading, disturbance, succession, 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.[6] Ecosystems in similar environments that are located in different parts of the world can end up doing things very differently simply because they have different pools of species present.[5] Internal factors not only control ecosystem processes but are also controlled by them and are often subject to feedback loops.[5]

Resource inputs are generally 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.[5] Although humans operate within ecosystems, their cumulative effects are large enough to influence external factors like climate.[5]

Biodiversity affects ecosystem functioning, as do the processes of disturbance and succession. Ecosystems provide a variety of goods and services upon which people depend.

Contents [hide] 1 History 2 Processes 2.1 Primary production 2.2 Energy flow 2.3 Decomposition 2.4 Nutrient cycling 2.5 Function and biodiversity 2.6 Dynamics

3 Ecosystem ecology 4 Human activities 4.1 Ecosystem goods and services 4.2 Ecosystem management 4.3 Threats caused by humans

5 See also 6 Notes 7 References 8 Literature cited 9 External links

History[edit source]

The term ecosystem was first used in 1935 in a publication by British ecologist Arthur Tansley.[fn 1][7] Tansley devised the concept to draw attention to the importance of transfers of materials between organisms and their environment.[8] He later refined the term, describing it as "The whole system, ... including not only the organism-complex, but also the whole complex of physical factors forming what we call the environment".[9] Tansley regarded ecosystems not simply as natural units, but as "mental isolates".[9] Tansley later defined the spatial extent of ecosystems using the term ecotope.[10]

G. Evelyn Hutchinson, a limnologist who was 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 that mineral nutrient availability in a lake limited algal production. This would, in turn, limit the abundance of animals that feed on algae. 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 energy and material through ecological systems.[8]

Processes[edit source]

Rainforest ecosystems are rich in biodiversity. This is the Gambia River in Senegal's Niokolo-Koba National Park.

Flora of Baja California Desert, Cataviña region, Mexico

Biomes of the world Ecosystems are controlled both by external and internal factors. External factors, also 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.[5] Climate determines the biome in which the ecosystem is embedded. Rainfall patterns and seasonal temperatures influence photosynthesis and thereby determine the amount of water and energy available to the ecosystem.[5]

Parent material determines the nature of the soil in an ecosystem, and influences the supply of mineral nutrients. Topography also 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.[5]

Other external factors that play an important role in ecosystem functioning include time and potential biota. Similarly, the set of organisms that can potentially be present in an area can also significantly

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GitHub, Inc.

Font Awesome 5 brands github.svg GitHub logo 2013 padded.svg

Type of business Subsidiary

Type of site Collaborative version control

Available in English

Founded February 8, 2008; 11 years ago (as Logical Awesome LLC)

Headquarters San Francisco, California, U.S.

Area served Worldwide

Founder(s)

Tom Preston-Werner Chris Wanstrath P. J. Hyett Scott Chacon

CEO Nat Friedman

Key people Erica Brescia (COO)[1]

Industry Software

Employees 888[2]

Parent Microsoft (2018–present)

Website github.com Edit this at Wikidata

Alexa rank Increase 49 (12 July 2019)[3]

Registration Optional (required for creating and joining projects)

Users 40 million (Aug 2019)

Launched April 10, 2008; 11 years ago

Current status Active

Written in Ruby

GitHub is an American company that provides hosting for software development version control using Git. It is a subsidiary of Microsoft, which acquired the company in 2018 for $7.5 billion.[4] It offers all of the distributed version control and source code management (SCM) functionality of Git as well as adding its own features. It provides access control and several collaboration features such as bug tracking, feature requests, task management, and wikis for every project.[5]

GitHub offers plans for free, professional, and enterprise accounts.[6] Free GitHub accounts are commonly used to host open source projects.[7] As of January 2019, GitHub offers unlimited private repositories to all plans, including free accounts.[8] As of May 2019, GitHub reports having over 37 million users[9] and more than 100 million repositories[10] (including at least 28 million public repositories),[11] making it the largest host of source code in the world.[12]

Contents [hide] 1 History 1.1 Acquisition by Microsoft

2 Company affairs 2.1 Organizational structure 2.2 Finance 2.3 Mascot 2.4 Harassment allegations

3 Services 3.1 GitHub 3.1.1 Scope 3.1.2 Licensing of repositories

3.2 GitHub Enterprise 3.3 GitHub Pages 3.4 Gist 3.5 Education program 3.6 GitHub Marketplace service 3.7 GitHub Community Forum 3.8 GitHub Sponsors

4 Sanctions 5 Developed projects 6 Censorship 7 Prominent users 8 See also 9 References 10 External links

History[edit source]

This section is in list format, but may read better as prose. You can help by converting this section, if appropriate. Editing help is available. (August 2019)

GitHub at AWS Summit GitHub was developed by Chris Wanstrath, P. J. Hyett, Tom Preston-Werner and Scott Chacon using Ruby on Rails, and started in February 2008. The company, GitHub, Inc., has existed since 2007 and is located in San Francisco.[13]

The shading of the map illustrates the number of users as a proportion of each country's Internet population. The circular charts surrounding the two hemispheres depict the total number of GitHub users (left) and commits (right) per country. On February 24, 2009, GitHub team members announced, in a talk at Yahoo! headquarters, that within the first year of being online, GitHub had accumulated over 46,000 public repositories, 17,000 of which were formed in the previous month alone. At that time, about 6,200 repositories had been forked at least once and 4,600 had been merged.

On July 5, 2009, GitHub announced that the site was being harnessed by over 100,000 users. On July 27, 2009, in another talk delivered at Yahoo!, Preston-Werner announced that GitHub had grown to host 90,000 unique public repositories, 12,000 having been forked at least once, for a total of 135,000 repositories.[14]

On July 25, 2010, GitHub announced that it was hosting 1 million repositories.[15] On April 20, 2011, GitHub announced that it was hosting 2 million repositories.[16]

On June 2, 2011, ReadWriteWeb reported that GitHub had surpassed SourceForge and Google Code in total number of commits for the period of January to May 2011.[17]

On July 9, 2012, Peter Levine, general partner at GitHub investor Andreessen Horowitz, stated that GitHub had been growing revenue at 300% annually since 2008 "profitably nearly the entire way".[18]

On January 16, 2013, GitHub announced it had passed the 3 million users mark and was then hosting more than 5 million repositories.[19] On December 23, 2013, GitHub announced it had reached 10 million repositories.[20]

In June 2015, GitHub opened an office in Japan that is its first office outside of the U.S.[21]

On July 29, 2015, GitHub announced it had raised $250 million in funding in a round led by Sequoia Capital. The round valued the company at approximately $2 billion.[22]

In 2016, GitHub was ranked No. 14 on the Forbes Cloud 100 list.[23]

On February 28, 2018, GitHub fell victim to the second largest distributed denial-of-service (DDoS) attack in history, with incoming traffic reaching a peak of about 1.35 terabits per second.[24]

On June 4, 2018, Microsoft announced it had reached an agreement to acquire GitHub for $7.5 billion.[25] The purchase closed on October 26, 2018.[26]

On June 19, 2018, GitHub expanded its GitHub Education by offering free education bundles to all schools.[27][28]

Acquisition by Microsoft[edit source]

On June 4, 2018, Microsoft announced its intent to acquire GitHub for US$7.5 billion, and the deal closed on October 26, 2018.[29] GitHub will continue to operate independently as a community, platform and business. Under Microsoft, the service will be led by Xamarin's Nat Friedman, reporting to Scott Guthrie, executive vice president of Microsoft Cloud and AI. Current CEO Chris Wanstrath will be retained as a "technical fellow", also reporting to Guthrie. Microsoft had become a significant user of GitHub, using it to host open source projects and development tools such as Chakra Core, PowerShell, Visual Studio Code, and Windows Terminal and has backed other open source projects such as Linux, and developed Virtual File System for Git (VFS for Git; formerly Git Virtual File System or GVFS)—a Git extension for managing large-scale repositories (and itself has been adopted by GitHub).[25][30]

There have been concerns from developers Kyle Simpson, JavaScript trainer and author, and Rafael Laguna, CEO at Open-Xchange over Microsoft's purchase, citing uneasiness over Microsoft's handling of previous acquisitions, such as Nokia's mobile business or Skype.[31][32]

Some[who?] saw this as a culmination of Microsoft's recent changes in business strategy under CEO Satya Nadella, which has seen a larger focus on the sale of cloud computing services as its main line of business, alongside development of and contributions to open source software (such as Linux), as opposed to the Microsoft Windows operating system.[33][4][30] Harvard Business Review argued that Microsoft was intending to acquire GitHub to get access to its userbase, so it can be used as a loss leader to encourage use of its other development products and services.[34]

Concerns over the sale bolstered interest in competitors: Bitbucket (owned by Atlassian), GitLab (a commercial open source product that also runs a hosted service version) and SourceForge (owned by BIZX, LLC) reported that they had seen spikes in new users intending to migrate projects from GitHub to their respective services.[35][36][37][38]

Company affairs[edit source]

Organizational structure[edit source]

GitHub, Inc. was originally a flat organization with no middle managers; in other words, "everyone is a manager" (self-management).[39] Employees could choose to work on projects that interested them (open allocation), but salaries were set by the chief executive.[40][needs update]

In 2014, GitHub, Inc. introduced a layer of middle management.[41]

Finance[edit source]

GitHub.com was a start-up business, which in its first years provided enough revenue to be funded solely by its three founders and start taking on employees.[42] In July 2012, four years after the company was founded, Andreessen Horowitz invested $100 million in venture capital.[5] In July 2015 GitHub raised another $250 million of venture capital in a series B round. Investors were Sequoia Capital, Andreessen Horowitz, Thrive Capital and other venture capital funds.[43] As of August 2016, GitHub was making $140 million in Annual Recurring Revenue.[44]

Mascot[edit source]

GitHub's mascot is an anthropomorphized "octocat" with five octopus-like arms.[45][46]

Octocat, the mascot of GitHub The character was created by graphic designer Simon Oxley as clip art to sell on iStock,[47] a website that enables designers to market royalty-free digital images.

GitHub became interested in Oxley's work after Twitter selected a bird that he designed for their own logo.[48] The illustration GitHub chose was a character that Oxley had named Octopuss.[47] Since GitHub wanted Octopuss for their logo (a use that the iStock license disallows), they negotiated with Oxley to buy exclusive rights to the image.[47]

GitHub renamed Octopuss to Octocat,[47] and trademarked the character along with the new name.[45] Later, GitHub hired illustrator Cameron McEfee to adapt Octocat for different purposes on the website and promotional materials; McEfee and various GitHub users have since created hundreds of variations of the character, which are available on The Octodex.[49][50]

Harassment allegations[edit source]

In March 2014, GitHub programmer Julie Ann Horvath alleged that founder and CEO Tom Preston-Werner and his wife Theresa engaged in a pattern of harassment against her that led to her leaving the company.[51] In April 2014, GitHub released a statement denying Horvath's allegations.[52][53] However, following an internal investigation, GitHub confirmed the claims. GitHub's CEO Chris Wanstrath wrote on the company blog, "The investigation found Tom Preston-Werner in his capacity as GitHub's CEO acted inappropriately, including confrontational conduct, disregard of workplace complaints, insensitivity to the impact of his spouse's presence in the workplace, and failure to enforce an agreement that his spouse should not work in the office."[54] Preston-Werner then resigned from the company. In 2017 more allegations were made of discriminatory and unsupportive behavior at GitHub by a developer who had been recruited following a commitment by GitHub to improve its diversity and inclusivity.[55]

Services[edit source]

GitHub[edit source]

Development of the GitHub platform began on October 19, 2007