(CNN) Carolina Panthers quarterback Cam Newton raised his fist in a black-power salute after scoring a touchdown. Pittsburgh Steeler Alejandro Villanueva was joined on the field by his teammates this time.

And many San Francisco 49ers knelt during the National Anthem, although some put their hands over their hearts.

For the second consecutive Sunday, NFL players around the country and in London demonstrated in a variety of ways in response to President Trump's call for NFL owners to fire any "son of a bitch" who "disrespects our flag."

Former NFL quarterback Colin Kaepernick pioneered the protests last year when he took a knee during the anthem over what he said was social and racial injustice.

As they were last week, some players' protests were met with boos from fans.

Here's a roundup of highlights from stadiums around the league.

Boos in Baltimore

Before the Baltimore Ravens took the field against Pittsburgh Steelers, the public-address announcer asked the crowd to join the Ravens organization "to pray that we as a nation embrace kindness, unity, equality, and justice for all Americans," CNN affiliate WJZ reported

The Ravens took a knee, then stood for the playing of the National Anthem, the station reported. The crowd appeared to boo as players knelt.

If you didn't go to the game, this is what we did pre-game. I was proud to read this. pic.twitter.com/1C653C8hlP — Bruce Cunningham (@Bruce45Sports) October 1, 2017

Last week, fans also booed when the Dallas Cowboys, including owner Jerry Jones, took a knee before locking arms during the anthem.

The Steelers all took the field before the anthem and stood during the song. Many Steelers, including head coach Mike Tomlin and quarterback Ben Roethlisberger, were shown with their hand over their hearts.

So was Steeler tackle Alejandro Villanueva, a former captain in the Army and an ex-Ranger. Last week, while the rest of his teammates remained in the locker room during the anthem, Villanueva stood in the tunnel alone with his hand over his heart.

Fists raised in Cleveland

Some players took stronger stances.

Several Cleveland Browns players held their fists high during the anthem before their game against the Cincinnati Bengals. At least one Browns fan also raised his fist in the air while those next to him saluted or held their hands over their hearts.

Bengals players were shown standing. The broadcast didn't show any players from either team kneeling.

Lynch vs. Trump

Oakland Raiders running back Marshawn Lynch was spotted walking into Sports Authority Field in Denver Sunday wearing a T-shirt that read, "EVERYBODY VS. TRUMP," according to KGO, a CNN affiliate

Raiders RB Marshawn Lynch wearing an "Everybody vs Trump" T-shirt: pic.twitter.com/7aiCUbjLUD — Adam Schefter (@AdamSchefter) October 1, 2017

Lynch later sat on the bench, as he usually does, during the playing of the National Anthem before the game with the Denver Broncos -- the only Raider to do so, according to multiple reports.

JUST WATCHED Baker on NFL players' protest: It's outrageous Replay More Videos ... MUST WATCH Baker on NFL players' protest: It's outrageous 00:56

Taking a knee in London

A trio of Miami Dolphins players -- Kenny Stills, Michael Thomas and Julius Thomas -- also took a knee as the anthem played before their game against the New Orleans Saints at Wembley Stadium in London, England, according to CNN affiliate WFOR . The three players stood for the British national anthem, the station reported.

The Saints, including quarterback Drew Brees, were seen kneeling as a team before the anthem. Most Saints players stood while the anthem played, and some locked arms.

The New Orleans Saints team kneels before standing for the National Anthem in a game against the Miami Dolphins in London's Wembley Stadium.

Other players kneel, sit, wear T-shirts

Several Buffalo Bills players took a knee during the anthem before the game against the Atlanta Falcons; most Bills players stood with their arms linked. The Falcons, including head coach Dan Quinn, stood with their arms linked, too.

Detroit Loins players Jalen Reeves-Maybin and Steve Longa took a knee during the anthem before playing the Minnesota Vikings. Some Lions players locked arms, as well as the entire Vikings team, according to announcer.

Steve Longa, a linebacker with the Detroit Lions, takes a knee with teammate Jalen Reeves-Maybin during the National Anthem before playing the Minnesota Vikings in Minneapolis, Minnesota.

Before the game between the Indianapolis Colts and Seattle Seahawks, the Colts players released a statement saying the players who had previously knelt during the anthem "did not intend to disrespect our flag, our National Anthem or those who serve our country."

Rather, the players wanted to use their platform to raise awareness and talk about "about real equality, the injustices against black and brown people, police brutality, respect, unity and equal opportunity," the statement said.

"Our players are hurting, our people are hurting, our neighborhoods are hurting, and kneeling was a direct response to that hurt," the statement said.

A statement from our players: pic.twitter.com/B844SSbW73 — Indianapolis Colts (@Colts) October 1, 2017

During warmups, some Colts players, including quarterback Andrew Luck, wore black T-shirts with "WE WILL" on the front and "STAND FOR...EQUALITY, JUSTICE, UNITY, RESPECT, DIALOGUE, OPPORTUNITY" on the back.

The Colts were shown standing during the anthem with their arms linked on the TV broadcast. The broadcast showed Seattle Seahawks defensive linemen Michael Bennett, Cliff Avril, and Frank Clark seated during anthem; other Seahawks were standing. Other Seahawks also sat during the anthem, a photo from CNN affiliate KIRO-TV showed.

'Stay united, not divided'

Carolina Panthers teammates Thomas Davis and Jonathan Stewart joined in prayer on the sidelines before the team's game against the New England Patriots in Foxborough, Massachusetts, CNN affiliate WBTV reported.

Panthers linebacker Shaq Thompson sported blue shoes with the words, "Stay United, Not Divided." The shoes also featured black and white hands shaking hands, WBTV reported.

Carolina Panther Julius Peppers, who remained in the locker room during the anthem before the team's game last week, was on the field for the song Sunday.

Patriots players, including quarterback Tom Brady, stood during the anthem and rested their hands on the player next to them.

Newton stood for the anthem. He later raised his fist after scoring a rushing touchdown in the fourth quarter in the 33-30 win.

"It was to signify Black Power, but more importantly, I pray every night for God to give me a pinnacle to give people hope," Newton said after the game, according to a video of his post-game press conference posted on the official Panthers site.

"I did it to ... show black pride because I am an African-American," Newton said.

Newton said he also wanted people to see "the joy... that I go out there and play with."

'Embrace your differences'

About half the members of the San Francisco 49ers knelt during the National Anthem before their game against the Arizona Cardinals in Glendale, Arizona, while some of those kneeling also placed their hands over their hearts. Their teammates stood behind them, with one hand over their hearts and the other on the shoulders of the kneeling players.

The 49ers issued a statement saying the demonstration was meant to show unity, love and brotherhood.

"For more than a year, members of our team have protested the oppression and social injustices still present in our society. While some may not have taken a knee or raised a fist, we have all shared the desire to influence positive change," the team said.

A statement from the players, coaches, ownership and staff of the San Francisco #49ers pic.twitter.com/Rs2XCOiUeO — San Francisco 49ers (@49ers) October 1, 2017

"Our demonstration is simply a representation of how we hope our country can also come together by putting differences aside and solving its problems," said the team, which encouraged fans to "embrace your differences, find strength in them, and come together for the good of all."