Chapter 2Living things

Section 1: What is life (Part 1, pages 34-37)

• Organism = LIVING THING• Examples: yourself, a pet, insects, plants

• ALL LIVING THINGS SHARE THESE CHARACTERISTICS:

1. Cellular organizations2. Contain similar chemicals3. Use energy4. Respond to their surroundings5. Grow and develop6. Reproduce

Cellular Organization• All organisms are made of small building blocks called cells

• A cell is the basic unit of structure and function

• Cells are so small you need a microscope to see them

• Unicellular: single-celled organisms (Bacteria)• Multicellular: composed of many cells that are specialized

to do certain tasks• Example: in our body, muscle and nerve cells (work

together to keep us alive!)

The Chemicals of life• Cells are composed of chemicals

• SUCH AS…• Water (most abundant)• Carbohydrates (energy)• Proteins and lipids/fats (building materials)

• Nucleic acid : genetic materials, chemical instructions that direct the cell’s activities

Energy Use

• Cells of organisms use energy to do what living things must do• Example: Repairing injured parts

• An organisms cells are ALWAYS hard at work

Response to surroundings• Plants and all other organisms react to changes in

their environment

• STIMULUS: a change in an organism’s surroundings that causes an organism to react• Example: temperature, light, sound….

• RESPONSE: an action or change in behavior

• Example: A plant stem growing toward the sun. Stimulus?? Response??

Growth and development

• Living things GROW (getting larger) and DEVELOP

• Development: the process of change that occurs during an organisms life to produce more complex organisms

Reproduction

• Organisms have the ability to reproduce, or produce offspring that are similar to the parents

• Example: Robins lay eggs… that develop into young robins… that closely resemble their parents!

Life Comes from life• Living things arise from living things through

reproduction

• ….But, four hundred years ago people believed that life could appear from nonliving things… CRAZY!?!?!

• They called this… SPONTANEOUS GENERATION***the mistake idea that living things can arise from nonliving sources

http://www.youtube.com/watch?v=WNByRghR6sw

Redi’s Experiment

• Francesco Redi – Italian doctor (1600’s)

• He designed a CONTROLLED EXPERIMENT to show flies do not arise from decaying meat

• Who remembers what a controlled experiment is???• A scientist carries out 2 tests that are identical in

every respect except for one factor

Redi’s Experiment

• Left jar = UNCOVERED• Right jar = COVERED

• Manipulated Variable?• Whether or not the jar Was covered

Pasteur’s experiment• Louis Pasteur--- French chemist (mid-1800s)

• Some people still did not believe Redi… so Pasteur came up with a new experiment

• His experiment… demonstrated that new bacteria appeared in broth only when they were produced by existing bacteria

• Both experiments convinced people that LIVING THINGS DO NOT ARISE FROM NONLIVING MATERIAL

Pasteur’s experiment