When the f1 plants are allowed to self fertilize, they produced both yellow and green peas in the next generation. how is this explained?

In F2 generation homozygous dominant, heterozygous dominant and homozygous recessive offspring are obtained so they produced both yellow and green peas in the next generation

Explanation:

After the cross between two pure breeds having yellow and green pea all the offsprings in the F1 generation were heterozygous dominant for yellow peas.

                              Y    Y

                        y    Yy   Yy

                        y    Yy   Yy

So when these F1 plants are crossed than three types of genotype will be produced that is homozygous dominant(YY), heterozygous dominant(Yy), and homozygous recessive.

                                  Y    y

                            Y   YY  Yy

                            y    Yy   yy

So homozygous dominant and heterozygous dominant offspring will produce yellow peas because yellow is the dominant trait and homozygous recessive offspring will produce green peas.

in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".