Lesson L1 ~ Characteristics of Living Things & Cell Theory Science 8 Life Science Lesson L1 ~ Characteristics of Living Things & Cell Theory

Living Things Are Made Of Cells one cell (AKA single-celled or unicellular organisms) or more than one cell (AKA multicellular organisms) A cell is the basic unit of life. Cells can be seen using a compound light microscope (as we will in class) or a scanning electron microscope (more powerful and used by scientists).

Living Things Respond To Their Environment A stimulus is anything that causes a living thing to respond. External stimuli A hot pan is the stimulus for you to pull your hand away (response). Sunlight is the stimulus for a plant to turn towards it (response). Internal stimuli feeling of hunger/thirst are stimuli for animals to eat/drink (response).

Living Things Need Energy Living things require energy to carry out activities needed for survival (like responding to stimuli, growing, reproducing, moving, and sleeping). plants are producers (make their own energy using sunlight, water, and carbon dioxide) animals are consumers (must eat plants or other animals to obtain their energy)

Living Things Grow Unicellular organisms grow by increasing in cell size (to a point). Multicellular organisms grow by increasing in number for: growth and to replace cells that wear out and die.

Living Things Reproduce Living things produce more of their own species to replace older individuals that die. Unicellular organisms reproduce by dividing into two identical cells. Multicellular organisms reproduce by mating.

Living Things Must Get Rid Of Wastes Waste products from eating (feces), drinking (urine), breathing (CO2), etc. are dangerous if they build up in our bodies, so must have a way of getting rid of them!

Cell Theory The cell is the basic unit of life. All living things are made of one or more cells. All cells come from other living cells.