This document discusses the different levels of organization in living systems, from smallest to largest: organelles perform specific functions within cells; cells are the basic unit of structure and function; tissues are groups of the same cell type; organs are tissues working together; organ systems are groups of organs; organisms are entire living things made up of organ systems; populations are groups of the same organism type; communities are multiple interacting populations; and ecosystems include all communities and abiotic factors in an area.

1. Levels of Organization