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

Cells• A cell is a basic unit of structure and function in

an organism

How many cells are in this picture?

Unicellular Multicellular

• Single celled organism.• Bacteria • Amoeba

• Organisms composed of many cells.

• These cells are specific and programmed for

specific jobs.

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.

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?

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

Water

Living Space

Autotroph – make their own foodHeterotrph – must consume others

All organisms need water to

survive.

All organisms need a place to live – there is limited space on Earth.

Homeostasis

Homeostasis = Balance

The maintaining of a stable internal

condition.

How does this frog maintain homeostasis?