EvolutionEvolutionHow does that work How does that work

again?again?

Origins of LifeOrigins of Life Scientists have long Scientists have long

wondered where wondered where life first began.life first began.

Fossil and chemical Fossil and chemical evidence has led to evidence has led to the knowledge that the knowledge that single-celled single-celled organisms were the organisms were the first forms of life in first forms of life in an atmosphere full an atmosphere full of toxic gases.of toxic gases.

So what happened after So what happened after that?that?

From that soup, life began and continued.From that soup, life began and continued. The early organisms continued to The early organisms continued to

reproduce and made offspring that looked reproduce and made offspring that looked or acted different.or acted different.

We all started using proteins, breaking We all started using proteins, breaking down sugar, etc. down sugar, etc.

Humans, though, still had a lot to learn Humans, though, still had a lot to learn about how organisms reproduced to make about how organisms reproduced to make new ones.new ones.

Take a look at how we Take a look at how we thought bees were madethought bees were made

Weird huh? Yes, we were Weird huh? Yes, we were that stupid once!that stupid once!

But think about it: we But think about it: we knew that bees weren’t knew that bees weren’t human and didn’t human and didn’t reproduce sexually, so this reproduce sexually, so this was a good replacement.was a good replacement.

Experiments by Redi and Experiments by Redi and Pasteur determined that Pasteur determined that organisms must come organisms must come from other living from other living organisms. organisms.

ExperimentsExperiments

Redi proved that Redi proved that flies do not come flies do not come from rotting meat.from rotting meat.

Pasteur proved Pasteur proved conclusively that conclusively that spontaneous spontaneous generation does generation does not occur.not occur.

Natural SelectionNatural Selection

Darwin’s travels led him Darwin’s travels led him around the world. His around the world. His most important work most important work was done in the was done in the Galapagos islands.Galapagos islands.

In studying the endemic In studying the endemic organisms and organisms and comparing them to comparing them to those he already knew, those he already knew, he began to wonder why he began to wonder why they were so similar.they were so similar.

Natural SelectionNatural Selection

Natural selection is Natural selection is notnot evolution in itself. evolution in itself. Natural selection gives the means by which Natural selection gives the means by which

evolution occurs.evolution occurs.

In other words, scientists think In other words, scientists think that evolution occurs because of that evolution occurs because of natural selection. All of the natural selection. All of the evidence points in this direction.evidence points in this direction.

Natural SelectionNatural Selection

Darwin’s ideas had four basic steps:Darwin’s ideas had four basic steps:1.1. Organisms produce more offspring than can Organisms produce more offspring than can

survive.survive.2.2. In any population, individuals have In any population, individuals have

variations.variations.3.3. Individuals with certain useful variations Individuals with certain useful variations

survive in their environments and pass survive in their environments and pass these variations on to their children.these variations on to their children.

4.4. Over time, these variations make up most of Over time, these variations make up most of the population. These organisms can look the population. These organisms can look completely different from their ancestors.completely different from their ancestors.

So What Does This Mean?So What Does This Mean?

It means that organisms have It means that organisms have developed special adaptations that developed special adaptations that are necessary to survive in their are necessary to survive in their environments according to natural environments according to natural selection.selection.

Can you think of any organisms that Can you think of any organisms that have special adaptations to help have special adaptations to help them survive?them survive?

This sounds fishy to me, This sounds fishy to me, Bass!Bass!

Remember, evolution is a science and only Remember, evolution is a science and only presents what we know so far!presents what we know so far!

By combining what we know about early Earth By combining what we know about early Earth and how natural selection works, we can make and how natural selection works, we can make a hypothesis about how life got here.a hypothesis about how life got here.

Do we know how life got started – NO! That’s Do we know how life got started – NO! That’s why I can’t say your religion is wrong!why I can’t say your religion is wrong!

But we do have some ways to know that we all But we do have some ways to know that we all came from a similar origin.came from a similar origin.

Evidence for evolutionEvidence for evolution

Organisms can Organisms can develop metabolic develop metabolic changes over time. changes over time. Bacteria and Bacteria and viruses often viruses often evolve and our evolve and our remedies won’t be remedies won’t be as effective.as effective.

Artist rendition of flesh eating

disease.

Evidence for EvolutionEvidence for Evolution

MimicryMimicry When an organism When an organism

has a structural has a structural adaptation that adaptation that makes it appear like makes it appear like another organism.another organism.

These organisms These organisms have mutations that have mutations that allow them to act allow them to act like other like other organisms.organisms.

What kind of animal is this?

Do you see an animal here?

Here are some more Here are some more examplesexamples

Evidence for Evolution: Evidence for Evolution: ColoringColoring

CamouflageCamouflage When an organism When an organism

has an adaptation has an adaptation that lets them blend that lets them blend in to their in to their surroundings.surroundings.

These organisms These organisms have mutations that have mutations that let them look like let them look like other things in the other things in the environment.environment.

Where is the lizard?

Who’s here?

Other EvidenceOther Evidence

Fossils are remains Fossils are remains of organisms from of organisms from long ago and are long ago and are found in different found in different layers of rock. layers of rock.

Fossils can be any of Fossils can be any of these:these:

A. Cast

C. Trace

B. Imprint

FossilsFossils

We know that there We know that there were other organisms were other organisms on Earth because we on Earth because we have found their have found their fossils.fossils.

We can find their We can find their approximate age by approximate age by dating the rock they dating the rock they were found in.were found in.

Each fossil tells us Each fossil tells us something about the something about the organism.organism.

What we’ve learned from What we’ve learned from fossilsfossils

We know that the oldest living We know that the oldest living organisms came from the sea.organisms came from the sea.

We know that there was a period We know that there was a period when all life died out (~ 144 million when all life died out (~ 144 million years ago).years ago).

We know where certain organisms We know where certain organisms lived and what earlier ancestors lived and what earlier ancestors looked like.looked like.

AnatomyAnatomy

There are two types of structures that suggest There are two types of structures that suggest evolution.evolution. Homologous structures:Homologous structures:

Remembering that homologous means same, this is when Remembering that homologous means same, this is when organisms have the same or similar body structures. For organisms have the same or similar body structures. For example, most animals have hands.example, most animals have hands.

AnatomyAnatomy

Analogous structuresAnalogous structures These structures are found in different animals and These structures are found in different animals and

are not similar in structure, but have the same are not similar in structure, but have the same function.function.

EmbryologyEmbryology

Embryology deals with the development Embryology deals with the development of the embryo. Take a look at the next of the embryo. Take a look at the next slide. What kinds of organisms do you slide. What kinds of organisms do you see? What do you notice about them?see? What do you notice about them?

Although the pictures here are Although the pictures here are exaggerated and they are no longer exaggerated and they are no longer used as proof by itself, there are still used as proof by itself, there are still many similarities between the species.many similarities between the species.

BiochemistryBiochemistry

Biochemistry evidence for evolution is Biochemistry evidence for evolution is based on DNA evidence.based on DNA evidence.

Scientists use electrophoresis to Scientists use electrophoresis to determine similarities between organisms. determine similarities between organisms.

Organisms with similar DNA are more Organisms with similar DNA are more closely related. closely related.

Biologists used this information to create Biologists used this information to create the 6the 6thth Kingdom (Archaebacteria) because Kingdom (Archaebacteria) because they were so different from other kinds of they were so different from other kinds of bacteria.bacteria.

So why did you make us study So why did you make us study genetics and what does it have genetics and what does it have

to do with evolution?to do with evolution? Remember that organisms with Remember that organisms with

useful variations survive and pass on useful variations survive and pass on their genes.their genes.

Useful variations are those that help Useful variations are those that help them hide from predators or get them hide from predators or get food.food.

These variations are differences in These variations are differences in their genes.their genes.

What do genes have to do with What do genes have to do with it?it?

Each species has a specific group of Each species has a specific group of characteristics or a gene pool.characteristics or a gene pool.

As organisms breed, they pass along these As organisms breed, they pass along these genes. The genotypes don’t change much genes. The genotypes don’t change much which means the phenotypes don’t change which means the phenotypes don’t change much.much.

If a new genotype (a different phenotype) is If a new genotype (a different phenotype) is introduced to the population, it could possibly introduced to the population, it could possibly be bred out of the gene pool if it doesn’t help be bred out of the gene pool if it doesn’t help survival. If it helps survival, then it may stay survival. If it helps survival, then it may stay in the gene pool.in the gene pool.

So what?So what?

New variations or phenotypes are New variations or phenotypes are caused by different genotypes that caused by different genotypes that weren’t found in the gene pool before weren’t found in the gene pool before (either by mutation or an organism new (either by mutation or an organism new to the area).to the area).

If these new genotypes are popular and If these new genotypes are popular and are bred into the population, they will are bred into the population, they will stay in the gene pool and you’ll begin to stay in the gene pool and you’ll begin to see them more.see them more.

I still don’t get it, Ms. Bass!I still don’t get it, Ms. Bass!

Okay, what would happen if Okay, what would happen if a group of blond haired a group of blond haired people moved to Asia and people moved to Asia and people thought that blond people thought that blond hair was cool?hair was cool?

When the parents have When the parents have children, they will introduce children, they will introduce blond hair into the gene blond hair into the gene pool. (Bb)pool. (Bb)

If children from these If children from these families have children, there families have children, there is a possibility that they is a possibility that they could have blond hair, could have blond hair, introducing the blond introducing the blond phenotype to the population.phenotype to the population.

BB bb

Family 1

BB bb

Family 2

Bb

Bb

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