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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