AP BIOLOGY

Detailed explanation-1: -All living organisms are made up of one or more cells, which are considered the fundamental units of life. Even unicellular organisms are complex! Inside each cell, atoms make up molecules, which make up cell organelles and structures. In multicellular organisms, similar cells form tissues.

Detailed explanation-2: -All living organisms are composed of cells, from just one (unicellular) to many trillions (multicellular). Cell biology is the study of cells, their physiology, structure, and life cycle.

Detailed explanation-3: -There are some organisms with single cell, which are called unicellular organisms, in which various life activities are carried out by the single cell.

Detailed explanation-4: -All living cells sense and respond to changes in external or internal conditions. Without that cognitive capacity, they could not obtain nutrition essential for growth, survive inevitable ecological changes, or correct accidents in the complex processes of reproduction.