CHAPTER 1

The Science of Life

What is Biology??

• The study of life

• Biologists study questions about how living things work, how they interact with the environment , and how they change over time.

• http://www.youtube.com/watch?v=juxLuo-sH6M

Characteristics of Life

• How do we distinguish between the living and non living?

• Biologists have established that living things share 7 characteristics of life.

1. Organization & cells- All living organisms have some degree of organization. A cell is the smallest unit that can perform life’s processes. Some organisms are made up of one cell (bacteria) and some are made up of multiple cells (humans)

2. Response to stimuli- A stimulus is a physical or chemical change in the internal or external environment. Organisms must be able to respond and react to changes in their environment to stay alive.

3. Homeostasis- the maintenance of a stable level of internal conditions even though environmental conditions are constantly changing.

4. Metabolism- sum of all the chemical reactions that take in and transform energy and materials from the environment.

5. Growth & development- Growth of living things results from the division and enlargement of cells. Development is the process by which an organism becomes a mature adult.

6. Reproduction- Reproduction is essential for the continuation of species.

7. Change through time- The ability of populations of organisms to change over time is important for survival in a changing world.

• 6 kingdoms

Light Microscopes• Compound light microscope: microscope that shines

light through a specimen and has two lenses to magnify an image.

• Parts of a light microscope:- Eyes piece (ocular lens) : Magnifies the image

- Objective lens: enlarges the image of the specimen

- Stage: platform that supports a slide holding the specimen.

- Light source: light bulb that provides light for viewing the image.

• Compound light microscope:

http://www.youtube.com/watch?v=RKA8_mif6-E

Electron Microscopes

• Scanning electron microscope: passes a beam of electrons over the specimen’s surface. SEM provide three dimensional images of the specimens surface.

• Transmission electron microscope- transmits a beam of electrons through very tiny sliced specimen.