In 1958, the Cessna 150 was introduced as a 1959 model. It had a Continental O-200 engine rated at 100hp. It had a 12-volt electrical system and sold for $6,995 brand new.
In April 1977, Cessna introduced the 152. The plane is pretty much the same thing except for some new added features. They added a 28-volt electrical system to handle the load of additional avionics, added a new cowling with quick-release fasteners for easier access to the engine, redesigned fuel tanks to reduce unusable fuel to 1.5 gallons, and an oil cooler as standard equipment. The new Lycoming O-235-L2C engine offered 110hp that put out more power at lower RPMs (noise reduction).
Those are the basics... and somewhere along the road Cessna added electronic flaps. Cessna stopped production of the 152 in 1985 (I think it was because of all the lawsuits from stupid people suing frivilously...but then Clinton signed some law that protected small GA manufacturers from getting sued).