Lesson Plan

Lesson Preview | Objectives

Lesson Preview

There are two very special qualities of living beings.

  1. The element carbon plays a vital role. Carbon is the only element that can combine with nitrogen and hydrogen to from stable and very large molecules such as DNA and proteins. Carbon can also that combine with oxygen to form a gas. This is important because carbon dioxide is one of the waste products of living beings and because it is a gas, it is easy to expel from the body. As far as we know, carbon is the only element capable of forming the “backbone of life”. Other than the elements named above, life also depends on sulfur, potassium, sodium, iron, calcium and magnesium, chlorine and trace amounts of copper and selenium and other elements.
     
  2. Living beings are composed of cells. Some beings have just one cell; some beings have many millions or billions of cells. Cells are highly complex with thousands of chemical reactions occurring at any one time. How did living cells arise from chemical elements in the air, sea and land? Since we cannot go back in time to find out, scientists have simulated what they believe to be the initial weather, atmospheric and geological conditions of earth soon after it formed and believe that very slowly complex molecules were formed which over thousands of years began to self-replicate and later form cells. The oldest fossils of cells are 3.5 millions years old.
     

To learn more about the origins of life, go to http://www.pbs.org/wgbh/nova/origins /. Of special interest is the interview with astrophysicist Neil deGrasse Tyson. 

This lesson is an introduction to biological cells.

 

Objectives

This lesson will explain:

 

Next Page: Instruction

B. J. Subbiondo © 2004