Question

do gymnosperms also have endosperms and cotyledons?

Answer 1

Endosperm/nutritive tissue is where at least part of the food is stored in the seeds of either phylum. Cotyledons can photosynthesize and absorb stored food from the endosperm, and the sole function of the endosperm is to store food for the juvenile plant's first growth. Within the larger cotyledons of dicots is a larger nutrient store paired with less in the endosprerm but species with a single cotyledon store their nutrients primarily in the endosperm.
Gymnosperm tend to have smaller cotyledons than angiosperm and store the nutrients in a nutrient rich endosperm that surrounds the embryo.

In gymnosperm the nutritive tissue develops from the haploid, female gametophyte rather than a double fertilization, as in the angiosperms, so it is not exactly the same. Angiosperm endosperm is triploid, but the term endosperm is used for both nutritive tissues usually.