For example, in the RS232 here:
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No. Different people draw schematics differently. Sometimes it is obvious, but usually not. In the examples you gave, it is not obvious.
When it is marked, it is usually a text note next to the connector. Or sometimes it is in the part number, like "DB-9F" for a female connector.
Here's one general guideline. It applies to connectors on the outside of the instruments. If the connector supplies power or signal, it's usually a female (F). This is done prevent shorting the signal (to something in the outside environment). A female pin is harder to accidentally short than a male pin. One can figure out from the schematic what's input and what's output.
A mnemonic for this rule is Source Side Socket (SSS).
I would deduce that DB-9 connectors on your schematic are F. The common use of RS232 is for talking to PCs (directly or through USB-to-RS232 adapter). Connector on the PC side is M. Typically, the cable is F-to-M. So, the connector on the other side is F.
The definition of jack and plug is a common source of problems.
Basically, the jack is the female part and the plug is the male part. Officially, the reference designator for jack is "J" and and the designator for plug is "P". "CONNx" could be either I think, but I'm guessing it's the male connector looking at the schematic, as the female symbols tend to have filled circles. It's a bit of a minefield ;-)
There are many ways to indicate the polarity when drawing a schematic. Unfortunately the guy who drew yours doesn't seem to have used any of them:
That said, for some connectors there isn't even a perfect way to describe the part: the outer shell might be an "outie" while the inner pins are "innies" so that the male/female, jack/plug designations are somewhat ambiguous (you may know there's a standard for whether to desgnate by the shell or the pin, but does everyone who has to read your schematic know the standard?). Then only the part number gives a totally clear spec.