Causes. Sunburn results when the amount of exposure to the sun or other ultraviolet light source exceeds the ability of the melanin to protect the skin. Melanin is the skin's protective coloring (pigment).kin cancer usually appears in adulthood. But it is caused by sun exposure and sunburns that began as early as childhood. You can help prevent skin cancer by protecting your skin and your children's skin from the harmful rays of the sun.
The angiosperms, or flowering plants, are one of the major groups of extant seed plants and arguably the most diverse major extant plant group on the planet, with at least 260,000 living species classified in 453 families (Judd et al., 2002; APG II, 2003; Soltis et al., 2005).
Etymologically, angiosperm means a plant that produces seeds within an enclosure, in other words, a fruiting plant. The ancestors of flowering plants diverged from gymnosperms around 245â202 million years ago, and the first flowering plants known to exist are from 160 million years ago.raditionally, the flowering plants are divided into two groups, which in the Cronquist system are called Magnoliopsida (at the rank of class, formed from the family name Magnoliaceae) and Liliopsida (at the rank of class, formed from the family name Liliaceae).