Animal Organism: Animal Cells and Tissues
Grade 7 Biology — Understanding the building blocks of animal life
Big Idea
Every animal — from a tiny ant to a blue whale — is built from cells. Cells are the smallest units of life. Groups of similar cells working together form tissues, and tissues combine to build organs. Understanding cell structure and tissue types is the foundation of all biology and medicine.
1. What Is an Animal Cell?
An animal cell is a eukaryotic cell — meaning it has a true nucleus enclosed by a membrane. Unlike plant cells, animal cells lack a cell wall; they are enclosed only by a thin, flexible plasma membrane. This makes animal cells more flexible and able to take on many different shapes.
Key Definition
Eukaryotic cell: A cell that contains membrane-bound organelles, including a nucleus that houses DNA. All animal and plant cells are eukaryotic.