Chapter 2-Sec. 1: (What is Life?)

  • Learning Goal:
    The student will be able to…
    1. …define the six characteristics of all living things.
    2. …describe where living things come from.
    3  ...describe how living things survive.

    First, write down the vocab words. Then, click below to watch a video about what living things have in common.

    Living Things Video


    the basic unit of structure and function in an organism

    an organism that has only one cell

    an organism with more thna one cell

    stimulus a change in environment that causes an organism to have a response

    an action or change in behavior

    the process of change that occurs during an organism's life

    The Characteristics of Living Things

    Living things share important characteristics. All living things have a cellular organization, contain similar chemicals, use energy, respond to their surroundings, grow and develop, and reproduce.

    1. Cellular Organization

    All organisms are made of small building blocks called cells. A cell is the basic unit of structure and function in an organism. Cells are so small that you need a microscope to see them.

    Organisms may be composed of only one cell or of many cells. Unicellular, or single-celled organisms, include bacteria (bak tihr ee uh), the most numerous organisms on Earth. Multicellular organisms are composed of many cells that are specialized to do certain tasks. For example, you are made of trillions of cells. Specialized cells in your body, such as muscle and nerve cells, work together to keep you alive.

    2. The Chemicals of Life

    The cells of all living things are composed of chemicals. The most abundant chemical in cells is water. Other chemicals, called carbohydrates (kahr boh hy drayts), are a cell’s main energy source. Two other chemicals, proteins (proh teenz) and lipids, are the building materials of cells. Nucleic (noo klee ik) acids are the genetic material—the chemical instructions that direct the cell’s activities.

    Figure 1: Cellular Organization Like all living things, the frog is made of cells. Most cells are so small that you need a microscope to see them.

    3. Energy Use

    The cells of organisms use energy to do what living things must do, such as repairing injured parts. An organism’s cells are always hard at work. For example, as you read this paragraph, your eye and brain cells are at work. Your blood cells are busy moving chemicals around your body.

    4. Response to Surroundings

    Have you noticed that plant stems bend toward the light? Plants and all other organisms react to changes in their environment. A change in an organism’s surroundings that causes the organism to react is called a stimulus (plural stimuli). Stimuli include changes in temperature, light, sound, and other factors. An organism reacts to a stimulus with a response—an action or change in behavior. For example, has the sound of a car horn ever startled you? The sound was a stimulus that caused your response.

    5. Growth and Development

    Living things also 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.

    6. Reproduction

    Another characteristic of organisms is the ability to reproduce, or produce offspring that are similar to the parents. For example, robins lay eggs that develop into young robins that closely resemble their parents.

    Click below to figure out: Is it Alive?

    Is it Alive?