兩個(gè)that引導(dǎo)的是定語(yǔ)從句,引導(dǎo)詞分別是animals和those,兩個(gè)引導(dǎo)詞在從句中都是主語(yǔ),句子構(gòu)成是這樣的：
Animals (that could not adapt themselves to the environment) perished and those (that could)survived.
第一個(gè)括號(hào)里是animals的定語(yǔ),意思是：（那些不能適應(yīng)環(huán)境的）動(dòng)物；
第二個(gè)括號(hào)完整的應(yīng)該是that could adapt themselves to the environment,是those（代指animals）的定語(yǔ),意思是：（那些能適應(yīng)環(huán)境的）動(dòng)物；
整句話直譯的話是“不能適應(yīng)環(huán)境的物種遭到滅絕,能適應(yīng)環(huán)境的得以存活.”
其實(shí)就是“物競(jìng)天擇,適者生存”的意思.