Write a fact related to the given fact, based on the given topic word. Note that, your fact should have at least one word in common with the given fact. All facts in this task refer to scientific facts. Your related fact must form a chain with the given fact. Chains form when two facts connect together to produce the third fact. An example of a chain is: "pesticides cause pollution" (given fact) + "pollution can harm animals" (related fact) → "pesticides can harm animals" (connected chain). Avoid creating simple paraphrases of the given fact. While your generated fact should be related to the input fact, they must describe slightly different scientific phenomena. It's okay if your related fact includes some irrelevant information, provided that it has some overlap with the given fact and it contains some words corresponding to the provided topic.

Fact: Birds move their wings using muscles in the chest. 
Topic: bird type eagle.
Eagles are large birds.

Fact: fat is used to keep animals warm. 
Topic: warmth animal healthy.
Vegetation is required by many animals for warmth and security.

Fact: a mutation in the sex cells of a parent can cause a new trait to appear in the parent 's offspring. 
Topic: gamete sex cell.

Sex cells, also called gametes, are the sperm in males and the ova in females.