evolution unit

We the Galapagos Islands

Evolution Unit• Chapter 15, Darwin’s Theory of Evolution

– Puzzle of life’s diversity– Ideas that shaped Darwin’s thinking– Darwin presents his case

• Chapter 16, Evolution of Populations– Genes and variation– Evolution as genetic change– Process of speciation

• Chapter 17, History of Life– Fossil record– Earth’s early history– Evolution and multicellular life– Patterns of evolution


Why Care About Evolution?1. Curiosity about the origins of life, how all the

species came into being, how the living world came into being.

2. Curiosity about what may happen to the natural world in the future.

3. Predict what new life forms research will discover in the future.

4. Evolutionary theory can help predict which strains of flu, AIDS, and West Nile virus will be most deadly next year.

5. Desire to learn about all life, past, present and future.

6. Want to pass this biology class and the TAKS test.


Definitions to Know• Scientific Theory = a well-supported, testable

explanation of phenomena that have occurred in the natural world.

• Evolution = change over time, the process by which modern organisms descended from ancient organisms

• Is Evolution Fact or Fiction?– Scientists believe it’s Fact.

•Proof?– Fossils– Speciation– Geological evidence– DNA evidence– Etc.

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Charles Darwin (1809-1882)• British naturalist famous for his theories of

evolution and natural selection. • Like several scientists before him, Darwin

believed all the life on earth evolved (developed gradually) over millions of years from a few common ancestors.

• In 1831, Darwin took a trip around the world on the ship, the M.S. Beagle, where he collected evidence that led him to propose his famousTheory of Evolution.There’s a huge

tortoise lurking behind me, interesting. And he has weird birds on

his back.

Charles Darwin

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Darwin’s Voyage on M.S. Beagle

Starting point: 1831, England

Ending point: 1836, England

Darwin’s observations showed him there were patterns to the diversity of life on Earth. Organisms are adapted to the environment where they live.

Did you know there are no rabbits in Australia? No kangaroos in England? No monkeys in North America? No elephants in Alaska?

I spent 5 years on a ship, can you imagine

what that was like? What we all

smelled like?

Ewww, nasty.

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Fossils• Darwin didn’t just observe and collect living

animals, he also collected fossils.• Fossils = preserved remains of ancient organisms• This led to questions like….

– “Where did all these organisms go?” “Why aren’t they still here?” “Why do they resemble organisms we have living today?”

This is too much of a

coincidence.

Glyptodon = dead Armadillo= alive

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Neanderthal man- existed from about 250 to 30 thousand years ago

Homo erectus- existed around 1.8 million years ago

Homo hablis- existed 2.4 to 1.5 million years ago

Homo sapiens- existed from about 200 thousand years ago (TYA) to the present

Do we look alike?

Australopithecines- existed between 5 and 2 million years ago


The Galapagos Islands• The most important, influential stop

on Darwin’s trip was the Galapagos Islands

• 1000 km west of S. America, a cluster of islands isolated by miles of sea

• The islands had different climates, and therefore, had different varieties of animals and plants

1. Giant Tortoises2. Iguanas

3. Finches

That’s my friend Finchy!

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Animals Darwin studied:

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I’m lonesome

George


Galapagos Turtles

Pinta IslandIntermediate shell

Pinta

Isabela IslandDome-shaped shell

Hood IslandSaddle-backed shell

HoodFloreana

Santa Fe

Santa Cruz

James

Marchena

Fernandina

Isabela

Tower

Each turtle lives on a certain island, and their

shells are different, island-dependent!

Brilliant!

The shape of each turtle’s shell is different and the different shapes depend on the turtle’s habitat.

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Darwin’s Finches• Darwin also collected finches, birds, matching their

beak and body shapes with different islands- just like the tortoises.

• Beak shapes in the finches indicated their type of diet, what they ate, and this told him where they lived

Ground finchTree Finch

In other words, if you get separated from your own

species, you evolve or change in response to your

environment.

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The finches of the Galapagos Islands provide a classic example of Adaptive Radiation —the evolutionary process through which a single lineage gives rise to species occupying diverse environmental niches. In one model of how species form, geographical separation leads to evolutionary divergence (growing apart).

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Darwin’s Finches

FYI, each beak is designed for a

different purpose.

Leaves

Seeds

Insects Grubs

Tool using

Seeds and Fruit

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Scientists Who Influenced Darwin• Discovery of fossils helped shaped the

scientists of Darwin’s time• 2 biologists who influenced Darwin were

James Hutton and Charles Lyell, they helped scientists recognize that:1. Earth is many millions of years old (Hutton)2. The same natural process happening THEN are

still happening NOW (Lyell)• Jean Baptiste de Lamarck

– Living things have changed over time– Living things respond to their environments– Through either use or disuse, organisms acquired or

lost certain traits during their lifetime, and these traits

could be passed on to the next generation

Lamarck here, nicely done

Darwin!

Thank you. I’m pretty smart.

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Use it or lost itHi! I’m Crabby.

I want to be superior, how can I do that?

I know! I’ll grow a huge claw, and I’ll squash those

other crabs!

Look, it’s Crabby, what a jerk. Hey,

Crabby, you loser!

Let’s drop him!

You just wait! I’ll get you one day!

Stay away from me!

Ha Ha! Are you scared? Huh? Are you scared you little

twerps! The Next Day……

Where are you going? Run away! Run away!

Boy, dad sure did know what he was doing when he developed this huge

claw- weapon!

Yeah, thanks dad!

Eeek! It’s the C Gang, they won’t leave me

alone! Oh, I’ve GOT to grow that claw!


Thomas Malthus (1798)• English economist who introduced the concept

of human population growth and the problem of too many people, too little space

• Populations don’t grow uncontrollably, there is a limit to population growth

• Why do some survive and some die?She’s about to be shark bait. Sharks are perfect

predators, perfect killing machines.

Too many people, too little

space, let the shark have her!

Thomas Malthus

He has no heart, he’s a mathematician.

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What took him so long? 25 years later….• In 1858, Alfred Wallace sent Darwin an essay with the

same ideas about evolution! • They presented their work together at a conference,

but….• This pushed Darwin to publish

his work, before Wallace• The Origin of the Species

– Proposed a mechanism for evolution, called Natural Selection

– Presented evidence that evolution has been happening for millions of years

You stole MY idea! Cheat! Thief!

You’re famous and I’m not!

Shut up Wallace, you sore loser. Survival of the fittest

and all that.

I procrastinated, and came close to losing my chance for fame! And I

aged quite a bit.

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Artificial Selection and Natural Selection• Variation exists in nature and animal and plant breeders use

this through artificial selection– A farmer may like a see a plant with bigger tomato and

use the seeds of that plant for next year’s crop– Or he may breed the two best milk cows to get a cow

who is an even better producer of milk• Darwin’s greatest contribution was his concept of natural

selection• In the struggle for survival, the most fit- the fastest prey,

the strongest predator, the one with the sharpest claws, wins the game of survival. Survival of the fittest.

• Fitness = the ability to survive and reproduce in a specific environment

How is your fitness? Did you notice how fat Wallace was? NOT fit.

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Adaptation = any inherited characteristic that increases an organisms chance of survival

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Proof for Evolution• Fossil record = Darwin argued

that the fossil record provided evidence that living things have been evolving for millions of years

• Geographic Distribution of living species: Descent with modification, says that similar species in similar environments but in different locations, were products of different evolution paths

Beaver

Muskrat

Beaver andMuskrat

Coypu

Capybara

Coypu andCapybara

They all look like rats to me.

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Homologous Body Structures

• What does Homo mean?– Homo = same, similar

• Remember these? – Homozygous- same allele for a trait, tt, TT– Homologous chromosomes- same

chromosome, one from mom one from dad

Turtle Alligator Bird Mammal

Ancient lobe-finned fish

Homolgous structures all develop from the same

embryo tissues but have different functions in the

adult organism.

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Vestigial organs• Why do we need our appendix?• It’s useless now, but it may have served

some function in our past• Vestigial organs = organ with little or no

function, left over from the past, ex. appendix

If you can live without it, with no medical

help, then it’s useless!

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Ch. 16, Evolution of Populations• Why are we all so different?• Variation in populations is the raw

material for evolution• 2 main sources of variation:

– Mutations = any change in a sequence of DNA, some are harmful, some are beneficial and some don’t have any effect at all

– Gene shuffling = mixing of genes due to random sexual mating

• 23 pairs of chromosomes can produce 8.4 million different combinations of genes

• Crossing over during Meiosis

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Variation and Gene Pools • Genetic variation is studied in

POPULATIONS, not individuals• Members of a population share a Gene Pool• Gene pool = consists of all genes, including

all the different alleles that are present in a population– Why?– They descended from a common ancestor

• Relative frequency of an allele = number of times an allele occurs in a gene pool

• So, evolution is any change in the relative frequency of alleles in a population

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Natural Selection and Speciation• Natural Selection= (Dr. Malone’s definition)

when individuals who have what it takes survive and reproduce best; survival of the fittest, it’s a dog eat dog, you got to step on someone else to get where you want to go, world

• Founder Effect = when a population shrinks down to only a few members, then rebounds so all of the future members have the “founder’s” genes

• Speciation = when natural selection and other random effects lead to the creation of a new species– Reproductive Isolation = populations become

reproductively isolated from each other, so it leads to evolution of a new speciesThis is why cats and dogs can’t

have cat-ogs, or is it do-cats? Dogats? Cadogs?

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Write as much as you want from this paragraph

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If all our women moved to China, could we continue to

interbreed? Ha ha. Don’t think so!Speciation

• Behavioral Isolation = when two populations can interbreed, but their different behaviors, or reproductive strategies, just don’t turn each other on, get it?

• Geographic Isolation = two populations are separated by geographic barriers, like mountains or oceans and they can’t interbreed

Move mountain!

Move mountain!

It’s too far to fly!

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I say go for it!

•Temporal Isolation = two populations are separated by different reproductive times


• Paleontologists (pay-lee-un-TAHL-uh-jists) = scientists who study fossils, history written into stone

• The fossil record:– Provides evidence about the history of life

on Earth – Shows how species have changed over

time (evolved) • 99% the species that have lived on Earth

are extinct!!!!• Fossils form in sedimentary layers of rock

– Fossils at the top are younger than fossils at the bottom, common sense, or relative dating

Ch. 17, The History of Life

Help!

I’m extinct. There are and will be no others like me, it’s so

tragic.

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How old are Fossils?• Relative dating is comparing fossils with other

fossils to see estimate the age of each, but it’s not very precise

• Radioactive Dating- calculating the age of fossils based on the amount of remaining radioactive isotopes they contain

Do you remember? Isotopes = an element with a different number of neutrons in its atom

Carbon-12

C6

12

Carbon-14

C6

14Radioactive!!!

How many neutrons in C-14? 8

How many neutrons in C-12?

6

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Half-Life = length of time it takes for ½ of the radioactive atoms in a sample to decay

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Geologic Time ScaleEra Period Time

Permian

Era Period Time (millions of years ago)Period Time

(millions of years ago)

290 – 245

360–290

410–360

440–410

505–440

544–505

1.8–present

65–1.8

145–65

208–145

245–208

Quaternary Vendian 650–544

Tertiary

Cretaceous

Jurassic

Triassic

Carboniferous

Devonian

Silurian

Ordovician

Cambrian

You are HERE

Which era does Tyrannosaurus Rex belong to?

Jurassic

Era

1. Paleozoic Era2. Mesozoic Era3. Cenozoic Era

Geologists divide the time between Precambrian and the present into 3 eras:

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Patterns of Evolution• Macroevolution = large-scale evolutionary

patterns occurring over long periods of time• Important topics in macroevolution:

1. Extinction = over 99% of all species that have ever lived on earth are now dead, extinct.

2. Adaptive Radiation = a single species evolving over time into diverse forms that live in different ways

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Macroevolution Cont. 3. Convergent Evolution = unrelated organisms

come to resemble one another

4. Co-evolution = process by which 2 species evolve in response to changes in each other over time

-Predator- prey pressures, what food is available, pollination, etc.

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Macroevolution Cont. 5. Punctuated equilibrium = the pattern of long

stable periods of time interrupted by brief periods of more rapid change

Hee hee! I’m coming to get you!

Yikes! I’m outta here! He’s crazy!

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evolution unit

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