1. Characteristics of Life

2. What do these pictures have in common?

3. 6 Characteristics to Define Life
Made of one or more cells
Respond to stimuli in their environment
Maintain a stable internal environment
Reproduce
Need energy to stay alive
Grow
The processes carried out by an organism that are necessary for life are called metabolic processes.

4. Made of one or more cells
Cells are the basic building blocks of life.
They are the smallest unit that can perform all of the metabolic processes necessary for life.
One cell = single-celled organism (unicellular)
Many cells = multicellular organism
All cells share certain basic structures
Cell membrane- separates cell from its environment and controls what enters or leaves the cell

5. Respond to stimuli in their environment
A stimulus is a change that affects how an organism acts.
Ex: chemicals, light, hunger
The reaction is called a response. Many responses help keep an organism safe.
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6. Maintain a stable internal environment
Homeostasis- the act of keeping a constant environment inside an organism
Living organisms need ways to maintain their internal temperature, water balance, and acidity.
If homeostasis is not maintained, disease or death may occur.

8. Reproduce Reproduction is the production of offspring.
Many organisms reproduce sexually.
Offspring get traits from both parents
Some organisms reproduce asexually.
Offspring are identical to the parent

9. Need energy to stay alive
Most organisms get energy from food!
Producers (plants) use sunlight to produce their food (sugar) through photosynthesis.
Consumers eat plants or other consumers.
Organisms use energy to carry out all the activities that happen inside their bodies.
Energy keeps up an organism's metabolism.
Metabolism- all the chemical reactions that take place in its body.

10. Grow
Multicellular organisms increase the size and number of their cells.
Single-celled organisms just grow in size and when they get too big, they just divide.

11. Necessities of Life
Water
Air
Place to live
Food

12. Necessities of Life Water Air Place to Live
Cells need water to keep their inside environments stable
Most chemical reactions that happen in cells need water.
Air
Most organisms use oxygen to help them break down food for energy.
Other organisms use carbon dioxide to make food- ex: plants
Place to Live
All living things need a place to live that has everything they need to survive.

13. Necessities of Life Food
All organisms need food to get energy and nutrients in order to live and grow.
From food, organisms get the following molecules needed to survive:
Proteins- used to build or fix parts of an organism’s body or to help reactions within a cell
Nucleic acids- ex: DNA- stores instructions for the organism
Lipids- a form of stored energy Ex: fats and oils
Carbohydrates- provide and store energy for cells Ex: sugars and starches
ATP- the molecule that carries energy and is used by cells