Here's why:

* Cell line: A population of cells that are derived from a single cell and can be grown and maintained in a laboratory setting.

* Animal cell: A cell that comes from an animal organism.

So, a cell line derived from an animal is an animal cell line.

Some examples of well-known animal cell lines include:

* HEK293: Human embryonic kidney cells

* CHO-K1: Chinese hamster ovary cells

* NIH3T3: Mouse embryonic fibroblast cells

These cell lines are widely used in research for various purposes, including:

* Drug discovery: Testing the efficacy and toxicity of new drugs.

* Gene expression studies: Understanding how genes are regulated and how they affect cell function.

* Biotechnology: Producing proteins and other biological products.

* Basic research: Studying cell biology and disease mechanisms.