Yet the fact is we know very little about gorillas. No really satisfactory photograph has ever been taken of one in a wild state.

定语of one in a wild state与中心词photograph被谓语分割。

即...photograph of one in a wild state

1）表达一张照片为什么会有photograph of one这种奇怪的表达？ 以前没看到。

【答】这里，one 是代词，指代a gorilla，不是数词。

a photograph of one = a photograph of a gorilla

2）那么2张照片是否也可以说photographs of two呢？

【答】不可以，原因上面已解答。“2张某人的照片” 是two photographs of sb.

3）为什么不说 No really a/one satisfactory photograph ? 可以这么说吗？

【答】No 是否定photograph 的。由于no = not a/not any，所以修饰可数名词单数时，不能再加冠词或one。例如：

I have not a book. I have not any book. I have no book.