“I feel a keen sense not to become the next roadkill,” Dr. Raghavan said. “If we become second class, we become irrelevant over time.”

Dr. Raghavan said focusing on search missed the internet’s competitive landscape. He said numerous companies without search engines compete with Google, including TikTok, Expedia and Booking. “A bunch” of companies are cause for concern, he said, but “Amazon is one of the two most keep-awake companies.” The solution to staying ahead, he added, was relentless increases in research and development spending.

The depiction of Google as a company just trying to stay ahead of the pack from Dr. Raghavan and Michael S. Sommer, a lawyer representing Google who questioned him, sharply contrasted with the argument made by the Justice Department and 38 states and territories. For the last seven weeks, they have maintained that Google crushed competition by paying Apple, Samsung and other partners billions of dollars annually to keep its search engine the default on their web browsers.

The government has said that Google’s massive scale makes it impossible for other search engines to compete for contracts and users, and gives the company commanding power over online ads, allowing it to raise ad prices at will.

Google has said that its search engine is popular because of its quality and that users can easily change their default to another service such as Microsoft Bing or DuckDuckGo.