1.1a Living things are composed of cells. Cells provide structure and carry on major
functions to sustain life. Cells are usually microscopic in size.
1.1b The way in which cells function is similar in all living things. Cells grow and
divide, producing more cells. Cells take in nutrients, which they use to provide energy
for the work that cells do and to make the materials that a cell or an organism needs.
1.1c Most cells have cell membranes, genetic material, and cytoplasm. Some cells have
a cell wall and/or chloroplasts. Many cells have a nucleus.
1.1d Some organisms are single cells; others, including humans, are multicellular.
1.1e Cells are organized for more effective functioning in multicellular organisms.
Levels of organization for structure and function of a multicellular organism include
cells, tissues, organs, and organ systems.
1.1f Many plants have roots, stems, leaves, and reproductive structures. These organized groups of tissues are responsible for a plants life activities.
1.1g Multicellular animals often have similar organs and specialized systems for carrying out major life activities.
1.1h Living things are classified by shared characteristics on the cellular and organism
level. In classifying organisms, biologists consider details of internal and external structures. Biological classification systems are arranged from general (kingdom) to specific