How Are The Gymnosperms One Of The Successful Groups Of Seed Plants Of Worldwide Distribution?

Gymnosperm seeds are not enclosed by a ripened ovary versus the angiosperms; whose seeds are inside an ovary wall.  The naked seeds of gymnosperms are borne in cones and are not visible.  The extensive division of gymnosperms can estimate by their 60-70 genera with a total of 700-800 species all over the world.  The wordily distribution is related to their primitive origin.  For example Cycads are distributed throughout the world.  Since Ginkgo originally appeared to be confined to mountains of south-eastern China but it also successfully showed extensive artificial propagations making to say that it also has natural distribution.  Distribution of gymnosperms in the past was even much more extensive.  They were dominant in the Mesozoic era that is 245 to 66.4 million years ago.  In the Cretaceous period; that is 144 to 66.4 million years ago, evolution gradually displaced them by angiosperms.  But they are still successful in the Earth's surface for their abundance for example Conifer forests.  Their extensive distribution also makes them to occupy areas of the Earth with severe climate.  They are adapted to save water and their leaves are covered with a heavy and waxy cuticle.  The stomata of the leaves are sunken below the leaf surface making less evaporation.  These factors lead their natural distribution even more extensive.