Click here to view a 6 minute video on natural selection. 

Click here for a copy of flashcards with evolution-related vocabulary.

Think about your friends and family.  Do they all look the same?  We call skin color, eye color, the shape of our ears and noses traits.  Differences in these traits are called variations.  Where do these variations come from?  Variations in hair color, for example, can come from our parents or from hair dye.  When we inherit variations in traits from our parents, these qualities came from our parents genes.  Humans have about 24,000 genes located on our 23 pairs of chromosomes (our DNA).  Each gene carries the directions to put together amino acids to make proteins.   

These proteins are the workers in our bodies.  Some act as enzymes to help chemical reactions take place.  Many other proteins are structural and make up our bone, cartilage and muscle and form our anatomical features. Other proteins make up the pigments that give our skin and eyes their color. The original proteins made by genes are put together and modified (changed) in different ways in our cells until we end up with over 100,000 proteins is our bodies.  

What does this have to do with evolution?  Evolution can be defined as the slow change in a species over many generations. New variations arise when heritable mutations occur.  A mutation is any change in the sequence of DNA. Often these changes are local so our children cannot inherit them; some even cause cancers like skin cancer. Sometimes the changes can be inherited, like the gene that causes sickle cell anemia. Some new variations are called adaptations when the new gene sequence helps the organism survive to be old enough to have offspring. Again, sickle cell is a good example in humans of an adaptation.  If someone lives in a part of the world where the disease malaria is prevalent, having one copy of the sickle cell trait helps them resist the disease instead of dying from it.  Unfortunately, inheriting 2 copies of the sickle cell gene (one from each parent) causes sickle cell disease which is very painful and difficult and time-consuming to treat.   

PPT 8-2 is on the evidence for evolution. The environment around us changes significantly over many generations. New adaptations that help offspring survive can eventually cause enough changes that new species can develop.  Current examples are the ring species gulls, the Herring Gull and the Lesser Black-backed Gull. You and your 1st cousins have a common ancestor in your grandparents and probably share many similar genes and traits.  If you compare your genes to someone whose nearest common ancestor to you was 14 generations ago, you will likely find many more differences. There is sufficient evidence now to say the humans & chimps have an unknown common ancestor that lived over 5 million years ago, with many intermediate species which no longer survive either.