1. Living Things are Composed of Cells: Single-cell organisms have everything they need to be "self-sufficient". In multicellular organisms, specialization increases until some cells do only certain things. 2. Different Levels of Organization: Living things must be able to organize simple substances into complex ones. Living things organize cells at several levels: Tissue - a group of cells that perform a common function. Organ - a group of tissues that perform a common function. Organ system - a group of organs that perform a common function. Organism - any complete living thing 3. Living Things Use Energy: Living things take in energy and use it, for maintenance and growth. 4. Living Things Respond To Their Environment: Living things will make changes in response to a stimulus in their environment. A behavior is a complex set of responses. 5. Living Things Grow: Cell division - the orderly formation of new cells. Cell enlargement - the increase in size of a cell. Cells grow to a certain size and then divide. An organism gets larger as the number of its cells increases. 6. Living Things Reproduce: Reproduction is not essential for the survival of individual organisms, but must occur for a species to survive. All living things reproduce in one of the following ways: Asexual reproduction - Producing offspring without the use of gametes. Sexual reproduction - Producing offspring by the joining of sex cells. 7. Living Things Adapt To Their Environment: Adaptations are traits giving an organism an advantage in a certain environment. Variation of individuals is important for a healthy species.
