1. Characteristics of Living things (8) Biology: the study of life Organism: any living thing 1) DNA: all living things have DNA (Deoxyribonucleic acid) in their cells. DNA is the chemical genes are made of 2) Grow: all living things grow and develop 3) Respond: all organisms respond to stimuli Stimulus: a signal to which an organism responds 4) Cells: the smallest units considered fully alive, all organisms are made of cells Double helix

2. Example = Bacterial cell, unicellular, prokaryotic Example = corn cell, multi- cellular, eukaryotic

3. 5) Reproduce: all organisms reproduce Sexual reproduction: 2 parents Asexual reproduction: 1 parent 6) Maintain a stable Internal enviornment: most organisms need to keep conditions inside their bodies as constant as possible, even when outside conditions change Homeostasis: constant internal conditions that organisms maintain 7) Obtain and use Material and energy: all organisms must take in materials and energy to grow, develop, and reproduce Metabolism: the combination of chemical reactions through which an organism builds up or breaks down materials 8) Evolve: over generations, living things evolve, or change over time

4. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 22.7 Example: This evolutionary tree of the elephant family is based on evidence from fossils.