GLE 23 – Classify organisms based on structural characteristics, using a dichotomous key.

 All organisms are made up of cells. A cell is the basic unit of structure and function in an organism. Single-celled organisms, like bacteria, are unicellular organisms. Organisms composed of many cells are multicellular.

 The cells of living things are made of chemicals. The chemicals in cells include water (most abundant), carbohydrates (cell’s main energy source), proteins (building material), lipids (building material), and nucleic acids (genetic material).

 Organisms get energy from taking in and breaking down materials. The combination of reactions that break down and build up materials to provide a cell with energy is metabolism.

 All living things react to changes in their environment. A change in an organism’s surroundings that causes the organism to react is called a stimulus. An organism reacts to a stimulus with an action or change in behavior called a response.

 All organisms grow and develop. Growth is the process of becoming larger. Development is the process of change that occurs during an organism’s life to produce a more complex organism.

 Organisms reproduce in different ways. Asexual reproduction involves only one parent and produces offspring that are identical to the parent. Sexual reproduction involves two parents and combines their genetic material to produce a new organism that differs from both parents.