Binders by Tuesday

Be on Time

Be ready to Learn

Any problems with summer assignment

Due on Tuesday

Charles Darwin and Natural Selection

Charles Darwin

Question for Thought

Earth has millions of other kinds of

organisms of every imaginable shape, size,

and habitat. This variety of living things

is called biological diversity. How did all

these different organisms arise?

How are they related?

In your own words, describe what YOU think the theory of evolution

means…

??

???

Darwin’s Theory of Evolution

Evolution, or change over time, is the process by which modern organisms have descended from ancient organisms.

A scientific theory is a well-supported testable explanation of phenomena that have occurred in the natural world.

How did Darwin come up with his Theory

Voyage of

Patterns of Diversity

Living Organisms and Fossils

Darwin collected the preserved remains of ancient organisms, called fossils.

Some of those fossils resembled organisms that were still alive today.

Others looked completely unlike any creature he had ever seen.

And some seemed to have disappeared

Living Organisms and Fossils

 

As Darwin studied fossils, new questions arose. Why had so many of these species

disappeared?

How were they related to living species?

The Galapagos Island

The Galapagos today is an amazing place.

Animals live there that are found nowhere else on earth.This makes them endemicPerhaps the most famous of the endemic

birds are the finches, of which there are 13 different species

The islands are a natural laboratory, and one in which evolution can be observed.

EndemicsAmong the kinds of animals found here and nowhere else: 1 penguin species1 giant tortoise species1 marine iguana species7 species of lava lizard14 species of sea cucumber1 species of sea lion1 species of hawkseveral species each of

mockingbirds, doves, owls, flycatchers, and yellow warblers

16

The Galapagos IslandThe smallest, lowest islands

were hot, dry, and nearly barren-Hood Island-sparse vegetation

The higher islands had greater rainfall and a different assortment of plants and animals-Isabela- Island had rich vegetation.

Animals

Q1 Endemic means:

A: The end is imminent.

B: The species isn’t found anywhere else.

C: The species has very specific habitat requirements.

D: The species needs to be protected.

E: The species is extinct.

Darwin was fascinated in particular by the land tortoises and marine iguanas in the Galápagos.

Giant tortoises varied in predictable ways from one island to another.

The shape of a tortoise's shell could be used to identify which island a particular tortoise inhabited.

The Finches The 13 finch species include:

6 species of ground finches3 species of tree finches1 woodpecker finch1 vegetarian finch1 mangrove finch1 Coco Island finch

A warbler finch that looks more like a warbler than a finch (one of the tree finches).

The woodpecker finch actually uses cactus spines to dig grubs out of branches!

27

Peter and Rosemary GrantScientists Peter and Rosemary Grant have

studied many of these species for the past thirty years.

Spend months at a time on the islandsOften know every finch on an island

https://www.youtube.com/watch?v=mcM23M-CCog

28

Let’s take a closer look at their data

Graph showing the distribution of beak depths for medium ground finches in Year 1

30

Q1: What is the average depth of the finches’ beaks in Year 1?

A: about 7mm

B: about 8mm

C: about 9.5mm

D: about 10mm

E: about 11mm

31

How much was the biggest difference in beak depth?A: 2 mm

B: 4 mm

C: 6 mm

D: 8 mm

E: 10 mm

32

A Change in the WeatherYear 2 – what happened?

Like most years, some rain fell the first week of January.The rest of January, there was one small shower.The total rainfall for the entire year: 24mm.

In a normal year, 130mm of rain would fall.

In Year 1, 137mm of rain fell.

33

The ground finches feed on seedsYear 1 June: 1m2 of lava on the island has

over 10 grams of seeds.Year 2 June: 6 grams of seeds per m2.

Year 2 December: 3 grams of seeds per m2.

In the drought, the plants conserved their resources and did not produce new seeds.

Similarly, the finches did not mate and did not produce eggs in Year 2

34

Seeds

A variety of seeds are produced on the island.Finches prefer the softest seeds, which are the

easiest to open.

The seeds above are seeds of a plant called Caltrop, in the genus Tribulus.These are among the hardest to eat.It takes a medium ground finch with a beak at least

11mm long to open one.Ground finches with beaks that are 10.5mm long or

less haven’t even been seen trying to eat them.

35

Prediction?What do you think will happen to the size

of the finch population between Years 1 and 3? (Remember, Year 2 is a drought year.)

Sketch a rough graph of your prediction

36

Q2: What do you think a graph of population size would look like for Year 1 to Year 3?

A:

Time

TimeTime

Time

B:

C: D:

37

Another Year of ChangeOn one day in January of Year 3, more than

50mm of rain fell on the island .The plants finally flowered and produced new seeds.

The Grants and their colleagues returned to the Galapagos.They found the finch population had been decimated.No new finches hatched in Year 2.Only one finch born in Year 1 survived to Year 3.

38

Year 3 Data

39

Q3: What was the average beak depth in 1978? (Remember that the average beak depth in 1976 was 9.5 mm.)

A: Just under 7mm

B: About 8mm

C: About 9mm

D: Just under 10mm

E: Just under 11mm

40

Evolution is:A change in the frequency of an allele, such as an allele for beak depth, is the basic definition of evolution.

41

Q4: Did the finch population evolve from 1976 to 1978?

A: Yes

B: No

C: Maybe

D: I don’t know

42

Evolution by natural selection

The Grants first went to the Galapagos to take a quick snapshot of finch diversity.

Within only a few years, they saw natural selection.In the course of one season, the

beaks got 0.54mm deeper and 0.39mm longer.

43

Evolution by natural selection

The beak size and shape was changing, right before the Grants’ eyes!

This is definitely evolution as we defined it earlier.

44

Surprises?Two things surprised the Grants:

1. Evolution could occur quickly enough to observe within a few field seasons. Darwin believed that we did not have a

long enough lifespan to observe evolution.

A single weather event can cause evolution, if there are traits that affect survival and if there is variation in those traits.

45

Surprises?2. Evolution can occur at very small scales.

The Grants’ measurements were very careful.The birds weren’t used to humans, and so

were easy to catch and measureThey couldn’t see a difference in even

1mm between two finches, but their measurements could

And due to those measurements, they could find that 0.5mm was enough to make a difference between survival and death in a drought year

46

Q: If beak depth increased during the drought, primarily due to selective mortality, can we really say that this natural selection was driven by environment favoring the survival of birds with deeper beaks?

A: No. Beak depth changed due to birds dying, not to birds surviving.

B: Yes. Birds with deeper beaks survived at a higher rate than birds with shallower beaks.

C: I’m really confused.47

The Journey HomeDarwin Observed that

characteristics of many plants and animals vary greatly among the islands

Hypothesis: Separate species may have arose from an original ancestor

Ideas that shaped Darwin’s Thinking

James Hutton:

1795 Theory of Geological changeForces change

earth’s surface shape

Changes are slow

Earth much older than thousands of years

Ideas that Shaped Darwin’s Thinking

Charles Lyell

Book: Principles of Geography

Geographical features can be built up or torn down

Darwin thought if earth changed over time, what about life?

Lamarck

Lamarck’s Theory of Evolution

Tendency toward Perfection (Giraffe necks)

Use and Disuse (bird’s using forearms)

Inheritance of Acquired Traits

Are you still paying Attention?

Population Growth

Thomas Malthus-19th century English economist

If population grew (more Babies born than die)Insufficient living

spaceFood runs outDarwin applied this

theory to animals

Publication of Orgin of Species

Russel Wallace wrote an essay summarizing evolutionary change from his field work in Malaysia

Gave Darwin the drive to publish his findings

Natural Selection & Artificial Selection

Natural variation--differences among individuals of a species

Artificial selection- nature provides the variation among different organisms, and

humans select those variations they find useful.

http://learn.genetics.utah.edu/content/selection/artificial/ slide 4

Adaptation/Mutation/Natural Selection/ Selective Breeding

Examples Primate A

Primate B

Mutation

Adaptation

Natural Selection

Adaptation/Mutation/Natural Selection/ Selective Breeding

Examples Primate A

Primate B

Mutation Develops opposable thumb

Adaptation

Natural Selection

Adaptation/Mutation/Natural Selection/ Selective Breeding

Examples Primate A

Primate B

Mutation Develops opposable thumb Does NOT develop opposable thumb

Adaptation

Natural Selection

Adaptation/Mutation/Natural Selection/ Selective Breeding

Examples Primate A

Primate B

Mutation Develops opposable thumb Does NOT develop opposable thumb

Adaptation Because of his thumbs, primate A can now handle tools and has a better chance of survival

Natural Selection

Adaptation/Mutation/Natural Selection/ Selective Breeding

Examples Primate A

Primate B

Mutation Develops opposable thumb Does NOT develop opposable thumb

Adaptation Because of his thumbs, primate A can now handle tools and has a better chance of survival

Primate B is less adapted to his environment so it is more difficult for him to survive

Natural Selection

Adaptation/Mutation/Natural Selection/ Selective Breeding

Examples Primate A

Primate B

Mutation Develops opposable thumb Does NOT develop opposable thumb

Adaptation Because of his thumbs, primate A can now handle tools and has a better chance of survival

Primate B is less adapted to his environment so it is more difficult for him to survive

Primate A passes mutation on to his children

Natural Selection

Adaptation/Mutation/Natural Selection/ Selective Breeding

Examples Primate A

Primate B

Mutation Develops opposable thumb Does NOT develop opposable thumb

Adaptation Because of his thumbs, primate A can now handle tools and has a better chance of survival

Primate B is less adapted to his environment so it is more difficult for him to survive

Primate A passes mutation on to his children

Primate B produces more children without the opposable thumb

Natural Selection

Adaptation/Mutation/Natural Selection/ Selective Breeding

Examples Primate A

Primate B

Mutation Develops opposable thumb Does NOT develop opposable thumb

Adaptation Because of his thumbs, primate A can now handle tools and has a better chance of survival

Primate B is less adapted to his environment so it is more difficult for him to survive

Primate A passes mutation on to his children

Primate B produces more children without the opposable thumb

Natural Selection Many Generations later thoseOut number those without because environment. Today all primates

primates with opposablethey are better suited for theirhave opposable thumbs

Evolution by Natural Selection

The Struggle for Existence-members of each species have to compete for food, shelter, other life necessities

Survival of the Fittest-Some individuals better suited for the environment

Over time, natural selection results in changes in inherited characteristics of a population. These changes increase a species fitness in its environment

Evidence for Evolution

The Fossil Record-Layers show change

Geographic Distribution of Living Things

Homologous Body Structures

Similarities in Early Development

structures that have different mature forms in different organisms, but develop from the same embryonic tissue

Homologous Structures-

Evidence for EvolutionVestigial organs-organs

that serve no useful function in an organism

Vestigial organs in Human Body

Similarities in Early Development

Analogous Structures Structures of different species having similar

or corresponding function but not from the same evolutionary origin

Summary of Darwin’s Theory

Individuals in nature differ from one another

Organisms in nature produce more offspring than can survive, and many of those who do not survive do not reproduce.

Summary of Darwin’s Theory

Because more organisms are produce than can survive, each species must struggle for resources

Each organism is unique, each has advantages and disadvantages in the struggle for existence

Summary (cont.)Individuals best suited for the environment

survive and reproduce most successful

Species change over time

Summary (cont.)

Species alive today descended with modification from species that lived in the past

All organisms on earth are united into a single family tree of life by common descent

Can you make an ideal species for a

environment?

On a piece of paper number 1-5

Next to each number pick a letter A-E and write down one next to each number

You can repeat letters if you wish

Climate A=Hot and dry (example: desert),

B=Hot and rainy (example: tropical rain forest),

C=Moderate temperatures and high rainfall (example: deciduous forest)

, D=Moderate temperatures and low rainfall (example: grasslands)

, E=Below zero temperatures (example: tundra)

Type of Terrain A=Volcanic islands,

B=Swampy,

C=Mountains,

D=Flatlands,

E=Underground

Predators A=Large birds of prey,

B=Humans,

C=Cheetahs,

D=Wolves,

E=Bears

Food A=Fish,

B=Leaves of tall plants or trees,

C=Roots of plants,

D=Fast running animals,

E=Insects

Biggest Threat to Survival

A=Pollution,

B=Deforestation,

C=Disease,

D=Not producing enough offspring,

E=Lack of food or water

Your Job is to: Decide which adaptations would be suitable for

your conditions. Remember those with the most favorable conditions will survive and reproduce

Show how these adaptations are apparent on their species. Draw their ideal species fo the environment

Explain what those adaptations are and why they are desirable for that situation