英语翻译Weknowthateachplantandanimal,bynaturaltendency,producesfarmoreseedsandeggs,andseedlingsandyoung,thanisnecessarytomaintainitspopulation.翻译系为什么moreseedsandeggs,andseedlingsandyoung这两句间要加

　　英语翻译

　　Weknowthateachplantandanimal,bynaturaltendency,producesfarmoreseedsandeggs,andseedlingsandyoung,thanisnecessarytomaintainitspopulation.翻译系为什么moreseedsandeggs,andseedlingsandyoung这两句间要加逗号划分下句子成分

　　ApairofAmericanrobinsnestinonebackyardraisingtwobroodsoffoureach.Tenrobinswherethereweretwo.这句也给翻一下前面一句能看懂后面的看不懂where怎么翻译

　　翻译Evenman'scarefullyburiedpastgenerationseventuallyarereachedbythepowersofdecay-oflife.带s。用than是不是有比较的意思？