How Does Evolution Work?

1. How Does Evolution Work? Understanding Evolution through Natural Selection

2. Evolution Big idea Questions • Describe what is meant by evolution through natural selection. • Describe the development of the theory of evolution by natural selection. Include mention of Charles Darwin. • Identify the importance of variation within a population for the long-term survival of the species. • Explain what is meant by being “fit” from an evolutionary standpoint. • What support do scientists offer for the theory of evolution by natural selection? Include mention of fossils and genetics.

3. Charles Darwin • Known as the “father of evolution” because he proposed the idea of evolution through natural selection. • Most biologists today agree that Darwin’s theory was “the single best idea that anyone has ever had.” Think about why… • Here is a clip from the series “The 100 Greatest Discoveries in Science.” This theory was named THE #1 discovery of all time. If the link doesn’t work, please use the one on the wiki, Clip #1.

4. Evolution through Natural Selection • Let’s look at Darwin and his theory a bit closer… As you watch, please use the clip to answer some of the big idea questions. • Here is a bit of background on Darwin and his theory. If this link doesn’t work, please use Clip #2 from the wiki.

5. Evolution through Natural Selection • Definition of natural selection: • The process by which individuals that are better adapted to their environment are more likely to survive and reproduce than other members of the same species. • This is thought to be the reason for evolution, or changes toa species over time. • Also referred to as “survival of the fittest.”

6. Example of natural selection • This simulation illustrates how environmental change affects the process of natural selection. • In this game, you control the amount of pollution produced by a nearby factory. Notice how this environmental factor influences the bugs that live in the bushes nearby. • Click here for the interactive site. If this link doesn’t work, please go to the wiki and use that link. • Then, go to the video clip that explains this concept in a different organism, a mouse. Click here for the clip. If this link doesn’t work, go to the wiki and select the link called, Mouse Clip • Next, watch one of the most common examples of natural selection, the peppered moth – Click here to view. If it doesn’t work, go back to the wiki and select the Peppered Moth Clip.

7. Evolution through Natural Selection • Theodosius Dobzhansky wrote in the magazine American Biology Teacher (1973), “Nothing in biology makes sense except in the light of evolution.” • The theory of evolution by natural selection is significant because it pulled together observations from several different areas of science: - biology & genetics - geology (rocks) & paleontology (fossils) * We will discuss evidence later this week!

8. Evolution through Natural Selection • Darwin’s theory was also one of the first written under the modern, accepted mind-set of a theory: it was written to be provisional. • When Darwin authored On the Origin of Species, he assumed that his ideas would need to be altered to fit with other observations. • However, it hasn’t been altered. In fact, more and more evidence to support his ideas has accumulated.

9. Natural Selection • Evolution refers to the changes that occur over long periods of time in the characteristics and diversity of organisms. • Evolution is a process that happens over long periods of time. Darwin proposed that this is due to natural selection.

10. Natural Selection • The theory of evolution through natural selection is based on the fact that variation exists in a population. • Individuals that are better adapted to living in a particular environment will have an increased chance to survive and reproduce.

11. Reproduction & Natural Selection: Connecting Dots • Reproduction can come in two forms: asexual and sexual. • Mutations (along with the blending of genes through sexual reproduction) leads to variety among individuals in a population. • If an organism’s traits don’t match the environment, it could lead to extinction for the species. • If the adaptations are beneficial, the species will survive.

12. Clip, “How does evolution really Work?” • While watching this video clip, you will see how scientists have continued Darwin’s work to explore the idea of evolution through natural selection. • As you watch, please think about how you might answer the big idea questions posed to you. • How Does Evolution Really Work? This is clip #3 on the wiki if this link doesn’t work.

13. Natural Selection • Individual organisms can not change their characteristics in order to adapt, unless they learn new traits. • Evolution refers to the change that a species undergoes over time. • Fossils are the key to our understanding of these changes over the history of life on Earth. • We also have made advances in genetics that supports the theory.

14. Since Darwin • Evidence continues to accumulate to support Darwin’s theory of evolution through natural selection. • We will be examining two significant “chunks” of scientific discoveries that support the theory of evolution through natural selection. • This will be in the areas of genetics & fossils. • This will be specifically addressed in class later this week.

15. Clip, “Isn’t Evolution ‘Just a Theory?’” • While watching this video clip, please think about addressing the big idea questions posed to you. • Isn’t Evolution ‘Just a Theory?’” Use Clip #4 from the wiki if this link doesn’t play the video clip.

16. Pulling it all together • Hopefully you now see how reproduction (both sexual and asexual) is necessary for a species to survive. • In order to increase the species’ chance of survival, variety among individuals is beneficial. Variety can come from mutations in both sexual & asexual reproducers; sexual reproduction offers variety in the species in a different way from asexual reproduction. • When variety exists, natural selection can occur, which can change the adaptations within the species. • Based on the enviornment, these adaptations can lead to the evolution of the species.

17. Pulling it all together • Here’s another teacher’s explanation of all of these pieces put together…. Click here to have it explained. Or, if it deosn’t work, you can click on Clip #5 from the wiki, How Does Variety Give Rise to New Species. • You could also watch the Khan Academy explanation of this process if that would be helpful – click here for that clip. Or, go back to the wiki and find it above the list of clips we’ve been using for this lesson.

18. Next Steps • When you have reached this point, you should have information about many of the big idea questions on evolution. We will get the rest in the upcoming days. • In the meantime, you have two choices for the remainder of the period: (1) Start your frog comic – I will explain this to everyone if you don’t understand… yet  (2) Work on the Adaptations Chart we started last week.