仿佛要表示整个类属习惯上是用定冠词加单数名词的吧，应该是不可以用复数名词或用单数名词连用不定冠词的。譬如：
老虎有灭绝的危险。
正：The tiger is in danger of becoming extinct.
误：Tigers is in danger of becoming extinct.
误：A tiger is in danger of becoming extinct.
但下面这句如何讲解呢？
Internation measures have been taken to prevent the extermination of whales. 国际上已经采取手段预防鲸鱼灭绝。
▲你的句子完全正确：
Internation measures have been taken to prevent the extermination of whales. 国际上已经采取手段预防鲸鱼灭绝。
▲表示整个类属不仅能够用定冠词加单数名词，也可以用复数名词，但不可以用单数名词连用不定冠词。即：
老虎有灭绝的危险。
正：The tiger is in danger of becoming extinct.
正：Tigers is in danger of becoming extinct.
误：A tiger is in danger of becoming extinct.
请参见“英语语法网”下面这篇文章：
《定冠词的类别使用方法》
http://www.yygrammar.com/Article/200802/133.html
