How Does Evolution Work?

Part 1: Defining Evolution through Natural Selection

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.

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.

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.

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 (changes in a species over time).

• Also referred to as “survival of the fittest.”

Example of natural selection This simulation illustrates how environmental change affects

the process of natural selection. A quickly changing environment can put an organism in a

vulnerable position and present an evolutionary disadvantage. In this game, you control the amount of pollution produced

by a nearby factory. Observe how the pollution affects the trees and the

populations of different colored bugs that live in the trees. Enjoy! Click here for the interactive site. If this link doesn’t work,

please go to the wiki and use that link.

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)

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.

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.

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.

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.

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.

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.

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.

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.

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) Work on finishing the “Adaptations Chart” that is due tomorrow in class (Tuesday, May 14).(2) See your teacher to get your frog comic assignment. Your frog comic will be due on Thursday, May 16 in class. We will work on it in class on Tuesday, May 14.