Whether by chance or calculation, television series often provide remarkable reflections of the real world. Program forms, from situation comedies to action adventures, may remain the same, but content is always being adjusted to fit the changing times. As Nancy Reagan's glittering gowns gave way to Barbara Bush's sensible shoes, so ''Dynasty'' is about to be replaced by less upscale, possibly even gentler diversions. The shift in tone can surely be detected this fall in ABC's willingness to back a new series, ''Life Goes On,'' that has a retarded teen-ager role filled by a young man who was born with Down's syndrome. Why now? ABC insists it is only because this is a good family drama. Then, CBS has ''Peaceable Kingdom,'' starring Lindsay Wagner and set in a Los Angeles zoo. Environmental concerns and threats of species extinctions move to center stage on prime time. And at least one hourlong drama series, ''Wolf,'' also on CBS, will be offering the new kind of sensitive tough-guy hero who is evidently a role model of the 1990's. The message is clear: Rambo, get lost.

Oddly enough, these television excursions in more reality-oriented directions come at a time when major movies are preoccupied with fantasy. At the box office, this has been the summer of ''Batman,'' ''Ghostbusters II,'' ''Indiana Jones and the Last Crusade'' and a revival of Walt Disney's ''Peter Pan.'' ''Batman,'' as a camp comedy, was strictly a television commodity not too long ago. Now, it is television that seems capable of connecting more and more frequently with the everyday life of its audiences. This is no doubt connected to the medium's increasing prominence as a conveyor of news, even if primarily in the form of daily headlines and so-called reality fare.

Beneath simple, and often simple-minded, surfaces, television can be unexpectedly revealing. ABC's ''Roseanne,'' for instance, with its working-class characters, might be dismissed as just another sitcom variation of ''The Honeymooners'' or ''The Life of Riley.'' But Roseanne herself is decidedly different. She makes withering wisecracks about education in today's schools. She leads a labor walkout at the factory where she works. She is, in short, the kind of assertive, liberated woman who would have been unthinkable in sitcoms past. And the show's rise to the top of the ratings poll says something about the world around us.

A sea-change in prime-time entertainment has perhaps already been indicated in the emergence of ABC's introspective, angst-suffused series ''Thirtysomething.'' It may not be a ratings blockbuster, but it is the program people are talking about. The prime-time schedule for this fall takes a few significant steps in other new directions. As it happens, there is even a convenient clue as to overall substance. For the first time in some 25 years, no weekly series will be listed as an Aaron Spelling production. Gone, at least for the time being, is the Spelling label that has become synonymous with escapist entertainment, ranging from ''The Mod Squad'' in the 1960's to ''Charlie's Angels'' and ''The Love Boat'' in the 70's to ''Fantasy Island'' and ''Dynasty'' in the 80's. Anticipating what his audience wants, Mr. Spelling is partial to garment-industry comparisons. ''If they're wearing miniskirts,'' he once observed, ''would you sell them something below the knee?''

The networks, of course, are not about to dump escapism in favor of social realism. Plenty of bare and well-toned Malibu-beach muscles will be on display in NBC's ''Baywatch.'' And the time-tested young-cop/old-cop formula is about to be trotted out once again in ''Hardball,'' also coming on NBC. The few new ''reality'' formats on tap, those such as CBS's ''Rescue 911'' or ABC's Diane Sawyer-Sam Donaldson newsmagazine show ''Prime Time Live,'' which begins Thursday, have less to do with programming philosophy than broadcasting economics. Put bluntly, they are cheaper to make. And that's no small consideration as the three major networks try to halt steadily declining audience shares. Competition from cable, independent stations and video rentals is bad enough. Now more and more pressure groups are complaining about program content. What's a poor network executive to do?

Some industry observers are already concluding that the general outlook is for cautious, conservative programming, the kind that is comfortingly familiar. This seems to assume that television has steadily been able to come up with an ''All in the Family'' or a ''Hill Street Blues'' to launch every new season. But as it happens, the fall schedule, while using standard formulas, is moving in some decidedly unusual directions. Last fall, viewers were given, and then rejected, the return of familiar faces (Mary Tyler Moore and Dick Van Dyke) and hit-movie ripoffs (''Baby Boom'' and ''Dirty Dancing''). Coming up this autumn are not only ABC's family drama featuring a Down's syndrome teen-ager but a sitcom about a group of orphans (NBC's ''Sister Kate'') and two other sitcoms concerned with inner-city - read that black and Hispanic - youngsters (ABC's ''Chicken Soup'' and ''Homeroom'').

Of course, conservative and comforting programs are the mainstay of commercial television. Maybe one year westerns, the next year cop shows, but the basic melody seldom changes. No one knows that better than Mr. Spelling, whose exclusive contract with ABC once gave him control of fully a third of that network's regular prime-time schedule, as well as a third of its made-for-TV movies. While admitting that many of his shows added up to little more than ''cotton candy for the eyes,'' the producer, who grew up in Texas as the son of an immigrant, was always enthusiastically endorsing the American dream. Whether in ''The Rookies'' or ''Hotel,'' whites and blacks, rich and poor, humble and powerful came together and worked to make all our lives safer and more rewarding.

For Mr. Spelling, opulence was the ultimate escapism vehicle. The conspicuous wealth of ''Dynasty'' became television's perfect paradigm for the Reagan era. If the rich were getting richer and the poor poorer, Mr. Spelling's solution was to take everybody on a tour of Rodeo Drive in Beverly Hills. Anxiety and doubt are selfish indulgences, not to be encouraged in Spelling Land.

Today, however, the code word among many social commentators is ambiguity. Opulence has given way to concerns about drugs, AIDS, homelessness, the environment, continuing scandals in Washington and on Wall Street, just to mention the more prominent of current issues. Can it be purely coincidence that as Mr. Spelling's elegant, soothing ''Hotel'' gets closed down, NBC is opening up Mel Brooks's ''Nutt House,'' an establishment in which nothing works and the staff seems ready for carting to a mental institution? At a time when AIDS is killing more and more parents, it may not be entirely surprising that television would turn its attention to orphans, even if only in a sitcom. It's a start.

Clearly attempting to go in new directions, Mr. Spelling had focused his most recent efforts on ''Nightingales,'' in which nurses spent most of their time tending to sexual antics, and ''Heartbeat,'' about a group of women doctors, one of them a lesbian. Neither series was renewed for next season.

Not too long ago, a special report on one network's evening newscast focused on a small group of suburban men who met regularly to discuss their inability to express emotions freely. Embracing each other at the end of the session, something that once would have been unthinkable, they stressed how their behavior had been conditioned by media images. Men were supposed to be self-sufficient and tough, something like the rich entrepreneurs in Mr. Spelling's ''Hart to Hart'' and ''Matt Houston.'' An appeal was made to tone down the distorting heroics on prime time.

Television does seem to be paying attention. The hero of CBS's forthcoming ''Wolf,'' for instance, is a former narcotics detective who, after being set up to take the blame for a botched drug bust, disappears for two years. Returning to San Francisco, he has cut his hair, shaved his beard and sets about trying to salvage a relationship with his difficult father, an old-fashioned Italian immigrant. Played by Jack Scalia, Tony Wolf (born Lupo) is still tough but now more tolerant and thoughtful. He buys back his dad's fishing boat from the finance company. He acts as sympathetic referee between his old friend Connie, a protective mother, and her frisky teen-age daughter. In case anyone misses the point, Connie spells it out, telling Tony: ''You've changed. I didn't like it so much when you were a cop - all tough guy and no heart.''
Then there's ''Top of the Hill,'' also coming to CBS. This is from the Stephen J. Cannell production factory, which, unlike Mr. Spelling's, specializes in quirky, offbeat concepts, from ''The Rockford Files'' to ''Wiseguy,'' that stay curiously in tune with the changing times. The new series stars William Katt as a surfer-turned-Congressman who moves with his ideals to Washington only to find ''people with problems, people who don't get satisfaction from municipal, state or Federal authorities.'' Thrown into the winner-take-all arena of politics, he will realize that ''the world is full of compromises and contrasts - you just have to make the best deals you can.'' Here, then, is yet another, considerably less-comforting version of the American dream.

All of which is not to say that Mr. Spelling's absence from the scene is likely to be prolonged. In partnership with, among others, Danny Thomas, Leonard Goldberg and Douglas E. Cramer, he has evolved into a shrewd student of mass-public taste. He is already working on a reunion special for ''The Love Boat,'' which will be shown on CBS early next year, and a Rodney Dangerfield series that could get on NBC's schedule before the end of this year.

And the industry is painfully aware that television trends are written in sand. A few years ago, the sitcom was supposedly dead. Then along came Bill Cosby. This past season, comedies accounted for 11 of the top-rated 15 series. Mr. Spelling once put it this way: ''We are all Willy Lomans in this business. We make our trips to the networks and tell them an idea, and they either buy it or turn it down.''

Whatever happens, you can be sure Mr. Spelling will be making his trips to the networks. Jules Haimovitz, currently president of the Spelling organization, talks confidently about the company ''broadening out into different configurations.'' He mentions the prestige television movie ''Day One'' and a new syndication deal with the movie director David Lynch as representative examples.

Come this fall, the national audience could very well turn away from series about retarded or orphaned youngsters. But, obviously, pure escapism has been put on the back burner. Certainly, it is striking that reality and ambiguity are hot commodities - for the time being.