Fine points about the nature of bias current in oamps and experiments
The LM358 inputs are the bases of PNP transistors, so they source current related to the bias current of the front end. This will be a more-or-less constant current within the common mode range of the amplifier. If you go outside the CM range, the transistor may be biased off and won't source as much base current. This is generally true of bipolar-input op-amps, though some may sink current rather than source it (eg. everyone's favorite, the LM741). Here is the expected behavior of the input: 



as you can see it's close to -10nA (sourcing) near 0V common-mode voltage, with only a +/-25% variation for voltages between -14V and +12V (with +/-18V supplies). 

MOSFET-input amplifiers leak very little current across the insulator- what leakage there is will mostly be related to the protection network on the chip (usually not well documented). The TLC2272 schematic shows a differential pair of MOSFETs but there is a protection network on each input pin, and the single MOSFETs are probably each an array of individual transistors.  

JFETs have an isolation junction so that will leak, but often the current is rather small.