5 things that changed the world in 2015

More than 135 million people have been born since the clock struck midnight on January 1, 2015. Another 50 million have died. Paris was shaken by a horrifying terror attack and the 2016 race for the White House was shaken up by a candidate most experts scoffed at on the day he announced. Cuba and the United States began restoring relations for the first time in decades, Greece became embroiled in an epic financial debt crisis and a massive 7.8 magnitude earthquake took nearly 9,000 lives in Nepal, China, India and Bangladesh.

Here's a look at the people, actions, and moments that changed the world this year.

ISIS/Daesh:

The terror group that calls itself the Islamic State first rose to infamy in 2014 after releasing a series of increasingly disturbing and gruesome videos of members violently murdering captives. Now known interchangeably as ISIS (the Islamic State of Iraq and Syria), ISIL (the Islamic State of Iraq and Levant) and most recently Daesh (an acronym for the Arabic name al-Dawla al-Islamiya al-Iraq al-Sham) -- it has become the new face of terror with its violent and extreme attempts to establish a caliphate.

Inside what life is like under ISIS rule:



While the group has lost many members and territory gains this year thanks in part to nearly 10,000 U.S.-led airstrikes in Syria and Iraq, ISIS has continued to alarm citizens and politicians far beyond its borders with a series of attacks. The group claimed responsibility for organizing and planning the Paris attacks of Nov. 13 that took more than 100 lives. While it does not claim to have masterminded the December shooting in San Bernardino, Calif., leaders say the killers were supporters, and officials believe they were radicalized jihadists.

With its powerful use of social media and aggressive recruitment techniques, fighting and shutting down the terror organization will pose a continuing challenge to the U.S. in 2016 and possibly beyond.

Donald Trump:

Trump has been a household name for years, for his wealth, his buildings and his reality show -- but the real estate mogul became a powerful force in the Republican party in 2015 and now has a significant chance of becoming the next president of the United States. Having flirted with a run for president in the past, the majority of political pundits scoffed when Trump hinted he might run. His bombastic and brash announcement on June 16 drew similar initial reactions from election experts, who claimed his rambling style and politically incorrect comments about immigrants would sink his campaign before it even began.

Donald Trump and some of his biggest supporters on his campaign trail:



That mantra has been repeated ad nauseam in the ensuing months, as increasingly divisive comments began emerging from his mouth -- but despite what the so-called experts expected, Trump has managed to hold a solid lead over many rivals. Cruz has become the latest candidate to rival his numbers in some polling -- especially in Iowa where he's taken a lead -- but Trump continues to resonate with a significant number of both likely Republican voters and independent voters.

While it remains to be seen if he will become president, or even win his party's nomination. His successful six-month run as the top polling candidate has allowed Trump to successfully change the conversation around the race for the White House in the Republican Party.

Caitlyn Jenner:

It is rare, if not unheard of, that two reality TV stars could truly change the world, but for reasons far different than Donald Trump, Caitlyn Jenner managed to do that this year.

Jenner became an American athletic icon in 1976 by winning a gold medal in the decathlon at the Olympics in Montreal, appearing on Wheaties boxes as Bruce. Thirty years later, Jenner became a reality TV fixture as a member of the Kardashian clan, but it was her decision to publicly announce that she was a trans woman that turned her into an activist. Google searches for the term "transgender" skyrocketed after Jenner's closely-watched TV special with Diane Sawyer.

See Jenner's transformation since the 1976 Olympics:



She may still be cashing in on reality TV fame, but Jenner has also turned that fame and power into an opportunity to advocate for other trans people searching for acceptance.

%shareLinks-quote="Trans people deserve something vital: They deserve your respect. And from that respect, comes a more compassionate community, a more empathic society, and a better world for all of us." type="quote" author="Caitlyn Jenner" authordesc="at the ESPY's" isquoteoftheday="false"%

Charleston church shooting:

When 21-year-old Dylann Roof opened fired in a church in Charleston, S.C., he killed nine people in a violent outburst that his own writings would later reveal was an attempt to start a race war.

What he instead did was inspire a moment of unity across South Carolina and many other places in the South, eventually setting off a chain of events that led to the removal of the Confederate Flag from state property, a feat others had attempted in vain for years.

Look back at how Charleston reacted and came together in the aftermath of the shooting:



The debate over that flag has spread throughout the South since, with many other states and localities weighing in on the matter both positively and negatively. The flag's supporters have insisted it is a sign of heritage, and not hate, while opponents claim it is intrinsically linked to the racially-charged systems of slavery and segregation -- but the debate probably wouldn't have been happening in 2015 if not for the shooting.

Supreme Court's same-sex marriage decision:

The highest court in the land often issues rulings that have small and tiny impacts on a handful of American citizens, but this year's landmark ruling in the Obergefell v. Hodges case impacted millions of lives in a single instance. The Court's 5-4 decision legalized same-sex marriage nationwide.

Supporters celebrated that "love has won," while opponents worked on plans to reverse the decision and protect religious freedom for those who reject the legitimacy of same-sex marriages on religious grounds. Few figures in that battle were as divisive as Kim Davis, an elected clerk from Kentucky who refused to issue marriage licenses to same sex couples in her jurisdiction despite state order, and eventually went to jail for her convictions.

Relive the celebration after the Supreme Court's decision was handed down:



Marriage equality activists say their next battle lies in protecting adoption rights for couples, including those who aren't always married. Opponents, including some presidential candidates, are continuing to work on legal plans to reverse the ruling, with many arguing that the decision should belong to the states, which have held the power to regulate marriage in the past.