Natural Selection and the Evidence for Evolution

Evolution is… the changing of species over generations. * Once an organism’s DNA is set after fertilization it will not change. Individual cells may experience mutations, but they will likely die off (unless the mutation is a cancer). However, mutations to an organism’s sperm or egg could create a change in the offspring.

Fossil evidence formed the basis of early evolutionary concepts

Charles Darwin 1809-1882

The voyage of the HMS Beagle

Thomas Malthus All populations will grow faster than the food supply. What does that mean for those organisms that are part of that population?

How did Darwin apply these ideas to Evolution? Many species produce large amounts of offspring (more than the habitat can support). This leads to competition for food, living space, mates and shelter.

What is artificial selection? Breeding organisms with specific and desired traits to produce offspring with those same traits.

Dogs are a great example

As different as they look, they still belong to the same species.

What is natural selection? A mechanism for change in populations. This occurs when an organism with favorable traits survives, reproduces and thus passes on those favorable traits. We say that they were “selected” by nature for survival. Those without favorable traits were selected for extinction.

To this very day, this book generates strong feelings on both sides of the issue of evolution. This book was banned by many religious organizations.

One of the problems with acceptance of Darwin’s theory is that evolutionary processes are difficult to observe directly. Change only happens from one generation to the next and those changes are likely not even observable. With that in mind, what would evolve faster? An elephant or a bacterium?

Our understanding of genetics means that the definition of evolution should also include that it is a change in the gene pool of a population over time Traits that hindered an organism’s survivability die with them. Traits that helped an organism to survive and reproduce will be passed on and therefore become more common. This is called allelic frequency.

View Peppered Moth Video http://www.youtube.com/watch?v=LyRA807djLc

As the trees darkened due to the Industrial Revolution, nature “selected” the black moth for survival (in this case it was man that changed the conditions, but the idea is the same). At this point we would say that the “allelic frequency” of the color of the moths has changed.

An adaptation is… A trait that helps an organism to either survive or get mates. The goal of all organisms is to get their genes into the next generation and to block their competitors from doing so. Think of two examples of traits that an animal or plant has that helps it to either feed itself or spread their genes by getting mates. Write those in.

According to Darwin’s theory, adaptations in species develop over many generations.

What is mimicry? An adaptation that makes a species look like a more formidable or dangerous one

Examples of mimicry in nature

Monarch butterflies taste horrible to birds, but the Viceroy butterfly does not. Birds cannot tell the difference so they don’t eat either.

Plants will mimic, too. Not poisonous

What is camouflage? An adaptation that enables an organism to blend in with their surroundings (it can be used for hunting or hiding).

Physiological Adaptations Changes that help an organism to survive, such as disease resistance. Different from structural adaptations because they are invisible (chemical traits, such as blood type).

Fossils allow us to relatively date Fossils allow us to relatively date. They also provide a record of past life and show changes over time.

How sedimentary rock layers are formed; https://www.youtube.com/results?search_query=how%20sedimentary%20rock%20layers%20are%20formed&sm=3

How are fossils formed: https://www.youtube.com/watch?v=SEDfRy6DQns

Evolutionary biologists believe that structural similarities are evidence that… Some organisms share a common ancestor. What is that? What common ancestor do you and your cousins have in common?

Homologous Structures – Use the pictures below to help formulate an answer.

Analogous structures – Use the pictures below to help you formulate an answer.

Are the wings of a butterfly and the wings of a bird homologous or analogous? Explain your answer.

Vestigial Structures Go to the following website to help you explain vestigial structures and give an example of a vestigial structure in humans. http://3.bp.blogspot.com/-ChvT-1VSn0k/UsFesKo2-_I/AAAAAAAAAxA/FqFhVQP5HZw/s1600/Vitruvian+Man+-+Human+Vestigial+Structures.jpg

For #25 you have enough info to figure it out on your own.

4 sources to determine evolutionary relationships 4 sources to determine evolutionary relationships. The following slides give you hints.