Chapters 10Principles of Evolution

What in the world is it and what is that pink thing?

This is a star-nosed mole which lives underground.

The 22 fingerlike rays are used for finding food and its claws are used for burrowing. It’s eyes are basically useless therefore its hearing is sharp

Write down what you think it is and what the pink thing is for.

What is Evolution?

• Evolution is the gradual biological change in a species over time.

• It is based on the concept that modern organisms have descended from other organisms

What comes to mind when you hear or read the term “evolution”?

Human EvolutionHuman Evolution• 225 million years ago, the first mammal evolved• 65 million years ago, the first primate evolved (and the

dinosaurs went extinct)• 6 million years ago, the first hominid evolved (man like

primate)• 2 million years ago, the species Homo evolved• Homo sapiens ~ 50,000 years ago.

This concept of Evolution, that organisms shared a common ancestry didn’t happen over night.

It took many people and many years to form this theory

1. Carolus Linnaeus (1700’s) a. Proposed a system of organization of all living

things based on physical similarities

b. Proposed that organisms might have arisen from crossing between two similar species

c.c. SpeciesSpecies – a group of organisms that are able to reproduce fertile offspring.

- A mustang and a miniature horse can mate and produce a pony that can eventually reproduce because the two are from the same species (Equus caballus) .

- A horse and a donkey (Equus africanus) could reproduce but the mule will never be able to reproduce.

What would you do if the most important things you needed were up high and you were alone, without

anything to climb on?

2. Jean-Baptiste Lamarck (1809) a. Believe in decent from common ancestry

b. Proposed that organisms have a tendency towards perfection and needed to change to better fit in with their environment.

c. Through selective use and disuse of organs, organisms acquired or lost certain traits during their lifetime.

d. By passing on these acquired traits to their offspring, a species can change over

time.

Fossil evidence shows that the ancestors of the modern giraffe originally had shorter necks.

These shorter necked giraffes had eaten all the food on the lower branches & needed to get to the food higher up.

By stretching their necks, to get to the higher up leaves, after many generations, the giraffes acquired the long neck trait.

The following generations would all inherit the acquired trait.

What parts of Lamarck’s theory do you agree or disagree with?

1. A need to change (Tendency towards perfection)

2. Use and disuse (if you use it, it develops, if not, it goes away)

3. Acquired traits (we can acquire traits in our lifetime)

4. Inheritance of acquired traits (passing on things we acquire or develop in our lifetime)

How would Lamarck have explained how the sandpiper got its shape?

In 8th grade, you studied Earth Science. Here are a few review questions for you.

1. How old is the earth?4.6 Billion years old

2. What was the earth like when it first formed?

It was molten, then solidified, then water forms. It was HOT!!

3. When did life begin on earth?

3.6 billion years

4. Where the 7 continents always in the same place?Plate Tectonics and continental drift. Plate Tectonics and continental drift. The continents were all one big mass and then moved due to the movement of the mantel below.

5. Does the earth change today?

Volcanoes, earthquakes, hurricanes, global warming, ice ages, erosion, …

Evidence and concepts that helped shaped the concept Evidence and concepts that helped shaped the concept of evolutionof evolution

a)a) FossilFossil (traces of organisms that existed in the past) evidence showed that organisms can go extinct.

b) Catastrophismb) Catastrophism – natural disasters like floods, volcanoes, asteroids… have happened and could cause mass extinctions mass extinctions of organisms. Like what happened to the dinosaurs!!

Ice Age

Giant Astero

id

Did this happen all of a sudden?

c. GradualismGradualism• The earth is in layers that formed very slowly layers that formed very slowly & has been altered over altered over

time by forces of naturetime by forces of nature.

What does the image on the right tell What does the image on the right tell you about how the earth you about how the earth changed?changed?

d. Uniformitarianismd. Uniformitarianism• The events of earth’s

past are happening past are happening todaytoday

History of Charles Darwin

• 2/12/1809 – 1882

• Very wealthy - Married 1st cousin

• Studied medicine & theology but ended up being a naturalist.

Starting in 1831, he took a 5 year voyage on the HMS BeagleHMS Beagle as the ship’s naturalist, from England, around South America, to the Galapagos Islands, below Australia and and Africa, back to SA and then to England

Galapagos Is

   December 1831 - expedition leaves Plymouth    Crosses the Bay of Biscay and meets rough seas - Darwin is seasick    Unable to land at Madeira as the tides are against them    Unable to land at Tenerife as the islanders fear that disease has been carried from Britain    Crosses the Atlantic Ocean to Brazil, via the Cap Verde Islands and the equator    February 1832 - lands at Bahia (Salvador) in Brazil, where Darwin collects botanical specimens and comes across slavery for the first time    On to Rio de Janeiro where Darwin spends two months making observations. He collects 68 beetles in one day!    Next stop - Tierra del Fuego, and three natives and a Christian missionary are left behind to work with the islanders    On to the Falkland Islands where Darwin observes very simple tiny plant-like sea creatures

   June 1834 - the Beagle sails round the southern point of South America, in the stormy seas of the Straits of Magellan    On to the island of Chiloe and the Chonos group of islands, where Darwin observes active volcanoes    February 1835 - at Valdivia, Darwin experiences an earthquake, and visits nearby Concepcion where he finds the town  almost destroyed by the earthquake    September 1835 - the Beagle arrives at the Galapagos Islands, where Darwin collects some of his most important specimens, the finches which can only be found on these islands    January 1836 - the expedition reaches Australia    April 1836 - Darwin observes an atoll, a coral reef around a lagoon, in the Keeling and Cocos Islands    The expedition goes round the southern tip of Africa, via the stormy Cape of Good Hope, and crosses the Atlantic to complete work in Brazil    October 1836 - the Beagle arrives back at Falmouth and Darwin is reunited with his family

HMS Beagle

The Galapagos Islands

1000km west of S. America – Volcanic chain of Islands– Low islands were hot, dry & basically void of

life. – Higher elevations islands had a lot of rainfall &

therefore more variety of life

• Saw much variationsvariations amongst inhabitants of the different islands.– Unique land tortoises, plants, birds, marine

iguana... – Species differed from island to island,

especially the tortoise shells & the “little brown birds” (finches)

Could these all have come from one common ancestor and evolve to be better suited or

adapted to their particular environment on the island?

• Darwin was extremely seasick throughout the voyage!

• Published book: On the Origin of Species in 1858

How could Darwin have used some of the concepts from earlier scientists to develop his

theory of evolution by natural selection?

1.1. FossilsFossils– Shows that organisms from the past organisms from the past are

similar to organisms of todaysimilar to organisms of today

– Organisms have gone extinct

2.2. The earth is oldThe earth is old, not just a few thousand years old

– If the earth is at least 1 million years old, there is plenty of time for a species to change

– It’s really 4.6 million years old.

2.2. UniformitarianismUniformitarianism– The events of earth’s past are happening

today– He can see that the earth gets changed by

such events like earthquakes, volcanoes, fires…

3.3. GradualismGradualism– Darwin saw the layers of rocks on exposed

cliffs along with the fossils within these layers

4.4. CatastrophismCatastrophism– Though Darwin would not have known what

happened to the dinosaurs, he knew that they existed at one time & were now extinct.

– Questioned why organisms would go extinct

Suppose that when Apple came out with the new iPhone 6 and they only issued 5 new phones to each

store. What do you think would have happened?

Thomas Malthus Thomas Malthus (1798) stated that whenever a population gets too large, there are limited resources available to them.

Sooner or later, there will not be enough food, space, fresh water …

War, famine & disease are the only forces War, famine & disease are the only forces to keep the population size from to keep the population size from outdistancing food supplyoutdistancing food supply

Darwin questioned that if organisms produce far more offspring than can survive, what factors determine which ones survive and reproduce?

What was the purpose of crossing a horse with a donkey to get mule?

• The horse is large and can carry a heavy load over long distance but it isn’t very sure footed.

• The donkey is small but very sure footed and can walk on very narrow paths.– When the two are crossed hopefully the mule will be

mid-sized and sure footed.– Sometimes though, they ended up with a small, thin

ankled mule.

• This is artificial selection artificial selection – Process where humans change a species by breeding it

for certain traits.

• Darwin asked himself how nature goes about Darwin asked himself how nature goes about selecting which traits are the most desirable.selecting which traits are the most desirable.

Darwin puts it all together1.1. Natural VariationsNatural Variations

Inherited variations/differences exists between organisms w/i a populationpopulation (all the members of

the same species in a given area)

2. Populations over populate Populations over populate (Malthus)Organisms in nature produce more offspring than

can survive which leads to competition for limited resources among members of a species

3. Nature selectionNature selection The organisms with the desirable variations are

better adapted and out-compete those who are not.

4. Descent with Modification.Descent with Modification.Individuals with the best adaptations survive and

pass on the trait to the next generation.

Survival of the fittestfittest & Natural SelectionNatural SelectionThose members of the population w/ the best natural variations (adaptations), will survive & pass these traits onto their offspring. Those without the variations will not survive

““FitnessFitness is measured in the # of is measured in the # of grandchildren one has”grandchildren one has”

Nature selects which variations Nature selects which variations are the best suited to the are the best suited to the

environment.environment.

Peppered Moth Simulation

Natural Selection

In a population, there are variations

There is heredity. Survivors reproduce and are therefore fitter.

There is natural selection. Some are selected out, some aren’t

Descent with ModificationA new species/variety of only tan beetles

Natural Selection Lab

Gene pool

All the genes from a single population combined together

50:50 with our lab

Gene frequency

Number of times a particular allele occurs in the gene pool.

0.5: 0.5 at start of lab

We will watch the gene frequency change through generations of the:

Small Lima bean

Large Lima bean

Natural Selection LabGeneration 1 2 3 4 5 6

Total number of Beans in Bag 100 100 100 100 100 100

Total number of Small Lima beans 50

Total number of Large Lima beans 50

Number of Small Lima beans removed  

Number of Small Lima beans remaining  

Number of Large Lima beans removed  

Number of Large Lima beans remaining  

Total number of beans remaining in bag  

Frequency of Small Lima beans remaining in bag  

Frequency of Large Lima beans remaining in bag  

Key:___ = Small Lima___ = Large Lima

52 63 4110

.5

1.0

If you continued this lab through other generations, what do you think would have

happened to the gene frequencies?

• Small Lima bean’s gene frequency would continue to go up while the large bean’s would decrease over time.

• Eventually, there wouldn’t be many large beans so the small limas would be easier to pick off (that’s all there is now).

• The gene frequencies would then change again.

• If all the larges though were picked out, they would become extinct

Fossil Evidence

• Fossil evidence shows that living things have been evolving on earth for millions of years.

• Also showed that the geographic distribution of organisms lines up with the movement of the earth’s crusts & that newer (more modern) forms of fossilized organisms are found in the upper layers of rock

Comparing EmbryosComparing EmbryosWhich one of these is a human, chicken, turtle, fish or salamander?

•Early stages of development of many animals with backbones are very similar•Children of Evolution video

Grasping, swinging Walking Swimming Flying

Look at the bones of the four animals below. What do you notice about all of them?

Under each one, write down what the limb is used for in each animalBased on what you see above, what conclusion could you draw about the ancestry of the four animals?

Homologous Structures• Same structures but

different functions• Bones of our

forearm, the front flipper of a dolphin, the wing of a bat & legs of a dog.

• Could all four limbed animals with backbones have descended with modification from a common ancestors?Homologous structures

show common ancestry or divergence from a common ancestor.

Analogous StructuresAnalogous Structures have same function but different structure

• Have similar environments• Butterfly and Bird wing• Yam and potato – both are tubers

What do these structures indicate about common ancestry?

• Why did we have an appendix?• Why would a whale have hind leg bones?• Why do we have wisdom teeth and why are they a

problem now?• What’s with our coccyx?• When eating a chicken wing, what’s with the thumb?

Thumb

Vestigial organsVestigial organs– Structures which no longer have a

function to the organism.• Our appendix, hair, coccyx, wisdom teeth

These vestiges had a useful function at one time but since they are no longer of an adaptive use to the organisms, they have become reduced with time.

What about structures that are no longer in use?