What advantages do flowers give angiosperms over gymnosperms?

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In general, it makes the angiosperms more efficient in pollination and, therefore, in producing seeds. Most angiosperms have perfect or bisexual flowers, that is, both the male and female reproductive organs are borne on the same flower while these are separated in the gymnosperms. In the conifers which are gymnosperms, thousands of pollen grains will be needed to pollinate one female. The pollens are carried by the wind and having one pollen land exactly on the stamen is quite an impossibility. 

Many angiosperms have colorful petals. This attracts the insects and birds. As they move from one flower to another, they deposit the pollens on the stigma of another flower. The nectar that angiospermous flowers produce and the aroma emitted play the same role.

Ten percent of energy is transferred from sun to the level indicated.

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