Evolution Presentation for Biology Keystone

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 or Darwin (havent decided.)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 2/21/12Slide 16The Process of Natural SelectionOverproductionInherited variationCompetitionReproductionNatural selection occurs through the following steps:1) OverproductionThe Process of Natural Selection2) Inherited Variation3) Competition4) ReproductionParents 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 Variation3) Competition4) ReproductionPeppered 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 didnt 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 MothKeep 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 didnt become darker. They just tended to die out, allowing the dark moths to take over!Carrier Cc Dominant CC Recessive cc

When two carriers mate:

Ratio of Offspring:

Dominant: 75%

Recessive: 25%Carrier Bb Dominant BB Recessive bb

When a recessive & carrier mates:

Ratio of Offspring:

Dominant: 50%

Recessive: 50% And then back again

Long after the Industrial Revolution, pollution regulations have helped to clean the soot from Englands trees.And guess what happened to the dark mothsDark-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 Evolution1) What is Evolution?2) Natural Selection 3) Evidence for Evolution4) Evolution in Action

BorneoJavaNew GuineaAustraliaPacific Ocean

Alfred Russel WallaceWhile 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 DistributionWallaces ContributionsThe Wallace Line

BorneoJavaNew GuineaAustraliaPacific 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 DistributionMarsupialsPlacental mammalsThe Wallace Line

BorneoJavaNew GuineaAustraliaPacific OceanThe 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 DistributionEven 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.

Flightless Island BirdsEvidence For Evolution:I. Geographic DistributionFlightless 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 dont need to fly to survive.Examples: kiwi, penguin, & the dodo bird.

Homologous ForelimbsEvidence For Evolution:II. Homologous AnatomyIn fact, every one of these animals has the same basic forelimb structure: a shoulder blade bone, a single humerus, two forearm bones, followed by many wrist bones and digits.They all trace back to a common ancestor, the earliest tetrapods, which had this basic layout, almost as a template.Its just been gradually modified for different uses over millions of years.

r Radius, u Ulna, a Scaphoid, b Lunare, c Triquetrum, d Trapezium, e Trapezoid, f Capitatum, g Hamatum, p PisiformeHomologous FeetHuman (hand)DogPigCowTapirHorseEvidence For Evolution:II. Homologous AnatomyLooking at these feet up close gives you an idea of how similar they really are, bone for bone.

Homologous FeetHorseEvidence For Evolution:II. Homologous AnatomyHumanTapirIn the case of the horse, the entire middle digit which has been modified into the lower part of the leg, while the other digits became smaller and smaller until they are completely gone.A horses hoof corresponds to our middle fingernail while the knee actually matches up to our wrist bones.Evidence For Evolution:II. Homologous AnatomyOther ExamplesRemember, homologous traits are adaptations that are similar between species because both species share an ancestor with the adaptation. For example, the following species all have wings, because they evolved from an earlier bird ancestor with wings.

In this case, the three species have diverged from each other for long enough that their wings have gradually taken on different uses.

Bird wingBat wingEvidence For Evolution:II. Homologous AnatomyConvergent EvolutionNot all similarities between species are homologous, however, because not all traits are inherited from a shared ancestor.Although both birds and bats use wings to fly, when you look at their anatomy, its obvious that their wings are completely different. The similarity is not due to common ancestry. Rather, birds and bats have undergone convergent evolution.

Bird wingBat wingEvidence For Evolution:II. Homologous AnatomyConvergent EvolutionConvergent Evolution When two species evolve a similar adaptation not because of common ancestry but because they have become adapted to a similar environment, or use the trait for a similar function.In other words, they have both converged on the same adaptation in their own way.Birds and bats have both evolved wings because they both use them to fly. Rather than homology, this is called an analogous trait or simply, an analogy.species Aspecies Bspecies Aspecies BadaptationadaptationadaptationEvidence For Evolution:II. Homologous AnatomyHomology vs. AnalogyDiagram 1 below illustrates how the eagle and the penguin evolved their wings from earlier birds. Diagram 1Diagram 2Diagram 2 shows how birds and bats evolved their wings separately. Homologous traitsAnalogous traits

Evidence For Evolution:II. Homologous AnatomyMore Examples

Four legs: Homology or Analogy?This is a homologous trait because all of these species evolved from the earliest tetrapod, which also had four legs.Homology:

Evidence For Evolution:II. Homologous AnatomyMore ExamplesTwo eyes: Homology or Analogy?This is a homologous trait because all vertebrates have two eyes.

This allows some animals to see almost 360, and it allows humans to see in 3D.

Homology:29Evidence For Evolution:II. Homologous AnatomyMore ExamplesProtruding eyes: Homology or Analogy?This is an example of convergent evolution because not all reptiles and amphibians have this trait.

Frogs and alligators have evolved the same adaptation independently, but for similar use: to see above the waters surface.

Analogy:30Evidence For Evolution:II. Homologous AnatomyMore ExamplesAnalogy:

Many placental mammal species have corresponding marsupial species, which occupy the same ecological niche on other continents. MarsupialsPlacentalsThey are not related, however, and their similarities are due to similar environments and ways of life. This is, once again, convergent evolution at work. All of the placental mammals are more closely related to each other than to any marsupial, and vice versa. 31Evidence For Evolution:II. Homologous AnatomyWhat does it mean?Homologous traitsAnalogous traitsBoth homologous and analogous traits are excellent evidence for evolution, because they show how different species are related and how they evolved their adaptations for survival.Evidence for evolution:32Alfred Wallacehttp://www.youtube.com/watch?v=9xiGfpokTvI

2nd known man who agrees with the theory of evolution!

Darwinhttp://www.youtube.com/watch?v=n3265bno2X0

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 Migration PatternsHomologous Anatomy

Ms. Fisher 02/21/12