What are the parts of kernel?

Yes, they are the interface to kernel functionality. To quote wikipedia: a system call is how a program requests a service from an operating system's kernel that it does not normally have permission...

No. It's a package. It certainly depends on parts of the kernel such as the network stack etc

endosperm germ or embryo pericarp

A grain is composed of three distinct parts. These are the bran, endosperm, and germ. The bran is the outer layer. It is composed of fiber and covers the endosperm. The endosperm is the largest part...

Wheat kernels are made up of three components: endosperm, bran, and germ.