Explain how the atmosphere in the Cretaceous may have influenced the evolution of the Pinaceae (pines, firs, spruce) and that of the early angiosperm. Solution Cretaceous period caused a major diversification of plants. Previously gymnosperms and pteridophytes dominated the earth ecosystem .the angiosperms existed as small and herbaceous weedy. But by the middle cretaceous period they evolved into shrubs and small tress dominating over gymnosperms. This period saw the change in environmental conditions at the time of early angiosperms, the oxygen amount had risen and became approx 1.55 times which might have been helpful for angiosperms. By the end of cretaceous period angiosperms dominated over the ecosystem. The oxygen level caused huge fires in that period.and this period saw the origin of a fire resistant plant species, that is pine. The early pine trees evolved under the constant pressure of fire.this caused them to evolve and form cones that opened only during the time of fire, and get burnt and produce sprouts quickly after fire..

1. Explain how the atmosphere in the Cretaceous may have influenced the evolution of the
Pinaceae (pines, firs, spruce) and that of the early angiosperm.
Solution
Cretaceous period caused a major diversification of plants. Previously gymnosperms and
pteridophytes dominated the earth ecosystem .the angiosperms existed as small and herbaceous
weedy. But by the middle cretaceous period they evolved into shrubs and small tress dominating
over gymnosperms. This period saw the change in environmental conditions at the time of early
angiosperms, the oxygen amount had risen and became approx 1.55 times which might have
been helpful for angiosperms. By the end of cretaceous period angiosperms dominated over the
ecosystem.
The oxygen level caused huge fires in that period.and this period saw the origin of a fire resistant
plant species, that is pine. The early pine trees evolved under the constant pressure of fire.this
caused them to evolve and form cones that opened only during the time of fire, and get burnt and
produce sprouts quickly after fire.