Which type of cause for the release of greenhouse gases, has the biggest impact on living organisms in the 20th century? Is it natural or man-made?

If dd means heterozygous for dimpled chin, then that is the genotype; but the dominant shows through with only one capital, meaning they have a dimpled chin as the phenotype.if ff is recessive for free earlobes, then that genotype is homozygous recessive; they won't be free, they'll be attached as the phenotype because of the double dose of lower-case f.