Tuesday: February 21st Agenda1.) Brief Review from Friday:What do we know about evolution? What is

evolution?Evolution the process by which species gradually change over

many generations through natural selection. Natural Selection the driving mechanism behind evolution as

explained by Darwin. “Survival of the fittest.”2.) Continue where we left off on Friday with our PowerPoint and evolution

packets!3.) Show a short clip on Alfred Wallace.4.) End with brief recap/ assessment. Do you understand the objective today?

Objective for today:Through open discussion and utilization of my

PowerPoint, students will begin to understand the process of natural selection

and be able to provide evidence for evolution.

Ms. Fisher 2/21/12

The Process of Natural Selection

1) Overproduction2) Inherited variation3) Competition4) Reproduction

Natural selection occurs through the following steps:

1) Overproduction

The Process of Natural Selection2) Inherited Variation

3) Competition 4) Reproduction

Parents produce more offspring than will survive. Similarly, plants produce thousands of seeds even though only a few may germinate.

There are genetic differences in any population which result in many combinations of different traits among offspring. These traits are passed genetically from parents to offspring.

In any population, organisms must compete for resources to survive. Some individuals have traits which allow them to survive better than others; often referred to as “survival of the fittest”.

Those who have a survival advantage are more likely to reproduce and pass on their favorable genes and traits to successive generations, resulting in new adaptations and eventually new species.

The Peppered Moth StudyThe peppered moth study is a

perfect case study of natural selection in action.• In the early 1800s, a common moth

species in England had light-colored peppered wings, which helped it blend in with the light bark on the trees in the area.

• This camouflage trait helped the moth avoid being eaten by birds.

• In 1848, a new dark form of the moth began appearing, and by the turn of the century, the dark variety made up the vast majority of the moth population.

So what happened?Why did the light moths die off, while the dark ones flourished?

• Something must have changed that gave the dark moths a survival advantage.

• Scientists recognized that moths were changing in response to a change in their environment.

• Extensive air pollution from industrialization was causing the tree bark to darken with coal soot.

1) OverproductionThe Peppered Moth

Study2) Inherited Variation

3) Competition 4) Reproduction

Peppered moths lay many eggs, and out of those that hatch, the vast majority of them will be eaten and will not survive to lay eggs of their own.

Traits for light or dark color are passed on genetically, and moth offspring tend to have traits similar to their parents. However, within a population, some are lighter and some are darker.

Since there are so many moths, some will survive, but most will die. The ones that survive tend to be the ones that have traits favorable for survival, in this case, camouflage.

The moths that best blend in with their surroundings will be more likely to survive to adulthood and lay eggs, which will yield offspring with those same favorable camouflage traits.

Peppered Moth

Keep in mind:• No individual moth ever changed its color. Some moths simply survived

better than others, changing the allele frequency, therefore changing the appearance of the color traits among the entire population.

• In other words, the light moths didn’t become darker. They just tended to die out, allowing the dark moths to take over!

Can you spot the moth?

Can you spot the moth?

Peppered Moth

Keep in mind:• No individual moth ever changed its color. Some moths simply survived

better than others, changing the allele frequency, therefore changing the appearance of the color traits among the entire population.

• In other words, the light moths didn’t become darker. They just tended to die out, allowing the dark moths to take over!

CarrierDominant

or Recessive

… And then back againLong after the Industrial

Revolution, pollution regulations have helped to clean the soot

from England’s trees.

And guess what happened to the

dark moths…

Dark-colored moths started to be eaten more and more as the tree bark

lightened, eventually allowing the light moths to repopulate once again.

Section 3 of 4:

Evidence for Evolution

1) What is Evolution?

2) Natural Selection

3) Evidence for Evolution

4) Evolution in Action

3) Evidence for Evolution

I. Geographic Distribution

II. Homologous Anatomy

III. Vestigial Structures

IV. The Fossil Record

V. Embryology

VI. DNA and Genetics

Evidence For Evolution:I. Geographic Distribution

Geographic Distribution Related native species are found only where they could have migrated on their own.

The distribution of ancient fossils, such as Mesosaurus, across the continents is a perfect example of this, although Darwin had no way of explaining how they got there, since plate tectonics had not yet been discovered!

Evidence For Evolution:

I. Geographic Distribution

The island of Madagascar is another great example of a set of species that naturally occur nowhere else in the world, for example, about 100 different species of lemur, a group of primates that branched off from earlier monkey-like primates when Madagascar split off from the African mainland about 160 million years ago.

Madagascar • There are thousands of other species

completely unique to this island.• They are all most closely related to the

species found along the east coast of Africa, because they share common ancestors.

MadagascarAFRICA

Borneo

Java

New Guinea

Australia

Pacific Ocean

Alfred Russel Wallace

While Darwin was putting together his theory of evolution by natural selection, another British naturalist named Alfred Wallace was doing his own work in the East Indies, where he made some new discoveries about the species there.

Evidence For Evolution:

I. Geographic Distribution Wallace’s

Contributions

The Wallace Line

Borneo

Java

New Guinea

Australia

Pacific Ocean

• Wallace saw that the islands of the East Indies were home to two completely different sets of mammals: monkeys and other placental mammals on the islands to the northwest, and marsupials to the southeast.

• It was as if these two groups were divided by some invisible barrier that they could not cross even though the distance was less than 40 km across.

• Other species including many birds were clearly cut off by the line as well.

Evidence For Evolution:

I. Geographic Distribution

MarsupialsPlacental mammals

The Wallace Line

Borneo

Java

New Guinea

Australia

Pacific Ocean

The islands on either side of the line made up different geologic formations divided by a deep channel. The two groups, therefore, had never been connected.

Evidence For Evolution:

I. Geographic Distribution

Even though the climates were almost identical, the flora and fauna were drastically different on either side of the line because the species had evolved in isolation from each other, just as the species on Madagascar had been isolated from the mainland of Africa.

Alfred Wallacehttp://www.youtube.com/watch?v=9xiGfpokTvI

2nd known man who agrees with the theory of

evolution!

Flightless Island Birds

Evidence For Evolution:

I. Geographic Distribution

Flightless birds are another great example of evidence based on geographic distribution, because in most cases, their ancestry can be traced back to ancient birds who flew to the island from the mainland.

• When birds colonize an island with no predators, they often lose the ability to fly over time because they don’t need to fly to survive.

• Examples: kiwi, penguin, & the dodo bird.

Assessment: Objective for today:Through open discussion and utilization of my

PowerPoint, students will begin to understand the process of natural selection

and be able to provide evidence for evolution.

What are the four steps of natural selection?OverproductionInherited VariationCompetitionReproduction

What type of evidence do we have that supports the theory of evolution?

Fossils

Ms. Fisher 02/21/12