The part of a book that gives the author's purpose in writing the book and acknowledges assistance from others is:

The part of a book that gives the author’s purpose in writing the book and acknowledges assistance from others is called the preface.

Explanation:

answer; cattle ranching on the savanna,and forestry in the amazon;

answer; the smaller of the two reciprocal products of translocated chromosomes is lost; after several cell divisions, only the larger of the two translocated chromosomes remains,its reciprocal is lost;