instruction:
Generate an overlapping word between the given two sentences. When you find the overlapping words, they don't have to match exactly, e.g., "survival" and "survive" are valid overlapping words. Little words like "the" or "of" don't count! You must generate significant words which are not the stop words.
question:
Sentence1: a mutation in the sex cells of a parent can cause a new trait to appear in the parent 's offspring. 
Sentence2: Traits are initiated by mutation and recombination.
answer:
mutation


question:
Sentence1: harming an animal species has a negative impact on the population size of that species. 
Sentence2: the rarity of a species increases harm to population exponentially.
answer:
harming


question:
Sentence1: Endocrine glands include the pituitary, thyroid, parathyroid, adrenal, pineal and thymus glands. 
Sentence2: Some pituitary hormones can control the thyroid gland.
answer:

thyroid