My fourth grade teacher (in about 1971) read to our class a book about a zoologist couple and their two children (a boy and a girl) who went on an expedition together as a family to the Amazon jungle to discover animals. I think for a zoo, but maybe not. Each chapter was about a search for a different kind of animal (like an armadillo) describing its nature and its habits. The children had some thrilling adventures – for example, with a jaguar – from which they were rescued by their parents. It was a series because I remember that there was another book where they went to Africa.