Characteristics of Living Things

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. Living Things Have Different Levels of Organization:

  • Both molecular and cellular 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.