SECTION 2-SECTION 2-Only the most AWESOMEST Only the most AWESOMEST

SECTION EVER!!!!SECTION EVER!!!!

(this is where you burst into applause and dance)

Darwin-He’s the manDarwin-He’s the man Darwin was born in

1809 and the world was bathed in sunshine and angels!

Darwin was not very good in school( that sounds really familiar, Einstein?)

He came from a pretty famous family: ◦ Erasmus Darwin(1731-

1802) was his granddaddy

◦ Josiah Wedgewood(1730-1795) was his other grandaddy who made fine pottery

Darwin’s boring familyDarwin’s boring familyRobert Darwin and

Susannah Wedgewood were his parents, and they raised their children in the Anglican Church

Darwin loved the great outdoors, which was fine, except that upper-class gentleman had to have some “real profession”.

Darwin’s EducationDarwin’s EducationEdinburgh

University 1825 for medicine..and he soon discovered it wasn’t for the faint of heart

Christ’s College in Cambridge (by his dad) to study for the clergy

While there, he became really fascinated with beetles, and nature stuff

Became really good friends with Botany professor John Henslow and Geology professor Adam Sedgewick

Darwin’s Two EpiphaniesDarwin’s Two Epiphanies#1- I guess he was

bored one day and picked up a copy of Zoonomia by Erasmus Darwin◦ He notes that

perhaps many characteristics of species had changed throughout the course of history and even came from a “single filament”

Darwin’s Two EpiphaniesDarwin’s Two EpiphaniesDarwin was with

Professor Sedgewick when a local workman discovered a fossil of a tropical mollusk

It annoyed Sedgewick because Wales was not a tropical place, so where did it come from? (this is a rhetorical question, cuz I know you can’t answer it…YET!)

Darwin Gets a Break: Onto Darwin Gets a Break: Onto the Beaglethe BeagleCaptain FitzRoy

was leading an expedition to South America about his ship the HMS Beagle

Henslow recommended Darwin, who got a job as naturalist on the Beagle

To prepare, he read Principles of Geology by Charles Lyell◦ Lyell claimed that

the extinct species that appeared in the fossil record were a result of Earth’s gradual changes that modified the conditions the creatures lived in

And here it comes….And here it comes….

Darwin makes an inference!◦ If species are always dying, but there are

plenty of other species on earth, new ones must have arisen…which means they could still be doing it.

So blah blah blah…preparations…technical details…reading…. And then they SET SAIL!

What happens in South What happens in South America, Stays in South America, Stays in South America.America.

They get to SA and near the Straits of Magellan, Darwin experiences an Earthquake ◦ The earthquake exposes fossilized

seashells, and he later discovers a petrified forest higher up and a fossilized horse tooth

BUT WAITHorses didn’t come to South America until

the Spanish came in the 16th century…curious…

IN 1835 the Beagle finally makes it to the Galapagos! ◦ He makes a great

observation: the animals and plants were unique to every island

◦ After this stunning observation, the packet rudely breaks off and talks about the journey back, so I suppose we have to move on…*sigh*

Home Sweet HomeHome Sweet HomeOn the way home,

the Beagle stops by the Cape Verde Islands. ◦ “Well that’s weird”

says Darwin, “The animals in Africa look an awful lot like the ones in South America…Captain, are you sure we’re near Africa?”

And now, passages of the And now, passages of the most boring book ever most boring book ever written, written, The Voyage of the BeagleThe Voyage of the Beagle

The only good thing about it is that it will put you to sleep several times in the course of a minute…for those of you who are tormented by thoughts of natural selection every night…

A reluctant summaryA reluctant summaryDarwin stops on the Galapagos Islands, all

of them, and makes long, frivolously detailed notes

*Note: all of these islands were caused by volcanic activity ◦ Chatham Island- Parched surface, little

vegetation, lots of craters. Darwin meets two large tortoises

◦ Charles Island- Small colony of Ecuadorians who hunt turtles. Darwin observes their numbers have fallen significantly.

◦ Albemarle-Found a salt lake and big black lizards

Summary continuedSummary continued

James Island- Stays with the natives and eats some of their delicacy (the tortoise) . He follows some Spaniards to a salt lake where he sees the skull of an unfortunate captain. Observes more similarities:◦ “Both in space and time, we seem to be brought

somewhat near to that great-that mystery of mysteries-the first appearance of new beings on this earth”.

◦ Observes rat species: “This rat is merely a variety produced by the new and peculiar climate, food, and soil, to which it has been subjected”

Darwin makes boring observations of the different bird beaks on the island, especially of Totanus=>

He describes some interesting reptiles native to the Galapagos, Amblyrhynchus◦ Notes the absence of frogs: “May this

difference not be caused, by the greater facility with which the eggs of lizards, protected by calcareous shells might be transported through salt water, than could the slimy spawn of frogs?”

Darwin’s tortoisesDarwin’s tortoisesThey are amazingly large, over 200

pounds!They travel long distances for

water, in line formation!Hypothesizes that tortoises’

bladders help them consume large quantities of water and that they are native to the Galapagos

As part of his naturalist role, Darwin takes a ride on one of the tortoises!!!

Amblyrhynchus (lizards)Amblyrhynchus (lizards)There are two species-

◦ A. cristatus (aquatic) “hideous”, black color, “stupid”

and sluggish Sun themselves on rocks Limbs adapted for crawling over

masses of lava Eat seaweed BUT, when it’s scared, it will not

enter the water!!! Darwin tested this out, read page

40!

Amblyrhynchus (lizards)Amblyrhynchus (lizards)The second species A. Demarlii, is

terrestrial ◦ Confined to central part of Galapagos

islands ◦ Yellow-orange on belly and brownish on top◦ “ from their low facial angle they have a

singularly stupid appearance”◦ They inhabit burrows and they cannot move

very fast because of the lateral position of their legs

◦ The lizard lives well with other animals—it allowed a bird to ride on its back

More zoological More zoological observations…as if we observations…as if we haven’t had enoughhaven’t had enough

Darwin basically takes inventory on page 42, and notes that the species of everything he collects is unique to the islands

But it’s still not nearly as impressive as St. Helena or Hawaii

I never thought I’d be so I never thought I’d be so happy to talk about plantshappy to talk about plants Look at the table

on page 44 for a summary of Darwin’s plant collections

“These species, having the same general habits, occupying analogous situations, and obviously filling the same place in the natural economy of this archipelago, that strikes me with wonder”

Darwin calls it a “creative force”

On the tameness of those On the tameness of those lame birdslame birdsThe birds appear

unafraid of humansDarwin thinks “it is

not acquired by individual birds in a short time, even when much persecuted; but that in the course of successive generations it becomes hereditary”

How is this different from Lamarck?

Congratulations! You Congratulations! You made it through a made it through a passage that most passage that most biologists shudder to biologists shudder to even think about reading!even think about reading!

And now, I will hand over the explanation of adaptive radiation to our beautiful little bird Fincha!

Tweet TweetTweet TweetTweet tweet tweet tweet tweet

tweet tweet Trill tweet tweet tweet tweet tweet Trill tweet tweet tweet

Tweet Tweet Tweet

Did you get all that?

ADAPTIVE RADIATION! ADAPTIVE RADIATION!

All about how cute little birds became cuter, or uglier, it depends…

The tree ofThe tree of life life

Four important questions all Four important questions all biologists think about at biologists think about at night:night:1. Origins: Where did the

ancestors come from, when and how?

2. Speciation: How and why are new species formed?

3. Diversity: Why are there x number of species?

4. Disparity: Why are these species as different or as similar as they are?

Talk to me Bird!Talk to me Bird!Finches arose in SA, but traveled

1000km to the GalapagosThe only living relative of the

finches we know of are grassquit genus Tiaris

The finches must have reproduced fast and often, because their doubling time is 750, 000 years

One species=Two One species=Two species?species?The allopatric model of

speciation developed by Leopold von Buch in 1825 can explain that. ◦And, just to throw a Russian name in

here, Theodosius Dobzhansky elaborated on it

◦The basic idea of allopatric model is that GEOGRAPHIC SEPARATION is needed for new species to form

There are three steps to There are three steps to allopatric speciation:allopatric speciation:

1. A species from the mainland colonizes an island and the population adapts to the environment by natural selection (remember, those who are most fit for that environment survive and reproduce, creating a population that is better fit!!)

2. A few members of the population colonize a second island and adapt to the conditions on that island—after a few generations, this species has become so different that they have diverged from the mother species.

3. the two species meet up again…and crazy things start to happen!!! There are three possible outcomes:

Three possible outcomes: Three possible outcomes: a) the members of the populations

will interbreed without loss of fitness

b) the members of the population will interbreed BUT they will lose fitness

c) the members of the populations will not interbreed at all

Sound cool doesn’t it? Sound cool doesn’t it? WRONG!WRONG!Except that this model makes a few wrong assumptions

Wrong assumption #1:Wrong assumption #1:The two species were separated

for a long time and then came to live on the same island

We now know that it doesn’t matter how far apart a population is from another, something called sympatric speciation The populations could overlap, but for different

reasons, evolve separately depending on ecological niche

Wrong assumption #2:Wrong assumption #2:The islands all existed at the time

of speciation.◦Biologists have traced back to three

million years ago, which is when the speciation started, and found as the number of islands increased, so did the number of finch species

◦So they have hypothesized that the finches arrived on the Galapagos at the start of the Ice Age—THIS IS A FREAKIN OLD SPECIES

The authors of this article have The authors of this article have something to do…other than something to do…other than stimulate us with their exciting stimulate us with their exciting informationinformationThey study seed-eating ground

finches on Daphne Major◦It all started in the drought of 1977

that prevented seed-producing plants from growing small beaked birds disappeared from the

population at a faster rate This is because the only seeds available

were larger, so big beaks=food

Ten years later…Ten years later…They repeat the experiment

when another drought occurred ◦But plants with larger seeds suffered

and small seeds dominated the food supply

◦So natural selection favored… or in other words, who was better adapted to this environment

Okay that was a major Okay that was a major tangent..back to speciationtangent..back to speciationWe can conclude that speciation

does not necessarily need geographical isolation, it needs reproductive isolation ◦ This can happen through mating songs and

visual features that would attract mates◦ Birds find mates by responding to the song

type of their fathers when it’s time for them to mate But there are limitations—songs are

learned, not controlled by genetics

So there are along of ways So there are along of ways bird songs can aid bird songs can aid speciation…speciation… The individuals that populate an

island have fragments of the songs they need

Sons can make errors in copying the song of their fathers

If it is transmitted better in the new environment, then it can repel males and attract more females.

Changes in body size and sound box can change the frequency of the songs

What to do when you can’t What to do when you can’t understand the organism understand the organism you are about to mate you are about to mate with….with….

You don’t mate. The chemistry just isn’t there. So everyone goes their separate ways, to

their own branch of the evolutionary tree.

There’s some hope There’s some hope though…though…Unless the song is extremely

different from the native song, females will recognize the song◦So what female finches don’t know

won’t kill them…then again…

A term you need to knowA term you need to knowEcological niche- the function of

a species within its environment◦Almost like a position in their

environment, how they fit in. ◦It gets really competitive keeping

these niches

So, what should you take So, what should you take away from section 2?away from section 2?

Darwin is awesome but…He writes too much, so…His book isn’t so awesome…but

we’re glad he wrote it becauseThat’s how we learned about

adaptive radiation of…Very cute finches!

The end of section 2!!!!

Congratulate yourselves Congratulate yourselves for not having anything for not having anything better to do than learn better to do than learn evolution…not like I do, evolution…not like I do, but just putting it out but just putting it out there. there.