What is Life?

Organisms = Living things

How do we know that something is a living thing?

Characteristics of Living Things Have a cellular organization Contain similar chemicals Use energy Respond to their surroundings Grow and develop Reproduce

Have a cellular organization

How many cells are in this picture? A cell is a basic unit of structure and function in an organism How many cells are in this picture?

Multicellular Unicellular Organisms composed of many cells. These cells are specific and programmed for specific jobs. Single celled organism. Bacteria Amoeba

Contain similar chemicals

The Chemicals of Life Carbohydrates Proteins Lipids Nucleic Acids

Water is necessary for life. If there is no water…there is NO life.

Get broken down into sugar (glucose). Carbohydrates Main source of energy. “Starches” Get broken down into sugar (glucose).

Proteins Help cells to build things. Muscle is made of protein. Protein is found in eggs and meat.

Lipids Help cells to build things. Fats and oils are lipids…sounds gross but you really need it!

Nucleic Acids Create genetic material DNA (deoxyribonucleic acid). The blueprint instructions for cells to direct all activity.

Use energy

Cells in organisms use energy to function. The students in this photo are using energy to learn. Even on the cellular level that we can’t see!

Respond to their surroundings

Clearly, this cat is responding to something that has scared it. All living things can respond to their environment A stimulus is what causes the organism to react. A response is what action happens as a result of a stimulus.

Grow and Develop

Living things can grow an develop. Development is the process of change that occurs during and organism life to produce a more complex organism.

Reproduce

All living things can produce offspring similar to themselves.

Spontaneous generation The idea that life can come from a non-living source. This was a very popular idea during the time of Francesco Redi. He created a controlled experiment to test if spontaneous generation was real.

Redi’s Experiment This is a controlled experiment. What is the control group? What is the variable group?

Life does not occur spontaneously. What is the conclusion? Life does not occur spontaneously. LIFE COMES FROM LIFE.

Louis Pasteur Wanted to re-test to see if spontaneous generation was true. (Most people still believed in it)

Pasteur’s Experiment This is also a controlled experiment. What is the control group? What is the variable group?

The Needs of Living Things Food Autotroph – make their own food Heterotrph – must consume others Water All organisms need water to survive. Living Space All organisms need a place to live – there is limited space on Earth.

The maintaining of a stable internal condition. Homeostasis Homeostasis = Balance The maintaining of a stable internal condition.

How does this frog maintain homeostasis?