Evolution Unit

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Evolution Unit

evolution – the process of biological change by which descendants come to

differ from their ancestors. 2

A change in an inherited characteristic of a population over time.

Individuals DO NOT evolve!

fossils – traces of organisms that existed in the past

Fossils gave evidence that species could become extinct.

catastrophism – theory that states natural disasters such as floods and volcanic eruptions have happened often during Earth’s long history

Evidence that the appearance of new fossils resulted from species’ moving into the area from elsewhere after the catastrophic event.

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Volcanoes, floods, and earthquakes are examples of catastrophic events that were once believed responsible

for mass extinctions and the formation of all landforms.

gradualism – theory that states changes in landforms resulted from slow changes over a long period of time, not a result of a catastrophic event

Evidence that canyons were a result of rivers cutting through rock

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Canyons carved by rivers show

gradual change.

uniformitarianism – theory that states geologic process that shape Earth are uniform through time (gradualism is constant and ongoing)

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Each layer of rock was

formed by the uniform laying

down of sediment that

still occurs today.

SCIENTIST CONTRIBUTION TO EVOLUTION

Linnaeus •1700s - Developed a classification system for alltypes of organisms known at the time System still used today•Studied differences in species – group of organisms so similar to one another that they can reproduce and have fertile offspring

Buffon •1700s - Proposed species shared ancestors instead of arising separately•Suggested Earth was much older than 6000 years

Erasmus Darwin (Charles’ grandfather)

•1700s – proposed all living things descended from a common ancestor and that more-complex forms of life arose from less complex forms

Lamarck •1800s – proposed that all organisms evolved toward perfection and complexity

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Think back to classification unit!

A Swedish botanist, physician, and zoologist, who laid the foundations for the modern biological naming scheme of binomial nomenclature. He is known as the father of modern taxonomy, and is also considered one of the fathers of modern ecology.

The establishment of universally accepted conventions for the naming of organisms was Linnaeus' main contribution to taxonomy—his work marks the starting point of consistent use of binomial nomenclature.

Kingdom, Phylum, Class, Order, Family, Genus, Species

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Debate over the age of the Earth was a heated debate

Most Europeans believed in the biblical age of the Earth (a few thousand years).

Georges Buffon proposes Earth was much older than 6000 yrs old Using fossils and comparing them

100 years before Darwin, Buffon, in his HistorieNaturelle, a 44 volume encyclopedia describing everything known about the natural world, wrestled with the similarities of humans and apes and even talked about common ancestry of Man and apes.

Buffon believed in organic change, he did not provide a coherent mechanism for such changes. He thought that the environment acted directly on organisms through what he called "organic particles".

Buffon also published Les Epoques de la Nature (1788) where he openly suggested that the planet was much older than the 6,000 years proclaimed by the church, and discussed concepts very similar to Charles Lyell's "uniformitarianism" which were formulated 40 years later.

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Was one of the leading intellectuals of eighteenth century England, a man with a remarkable array of interests and pursuits. Erasmus Darwin was a respected physician, a well known poet, philosopher, botanist, and naturalist.

He also presented his evolutionary ideas in verse, in particular in the posthumously published poem The Temple of Nature. Although he did not come up with natural selection, he did discuss ideas that his grandson elaborated on sixty years later, such as how life evolved from a single common ancestor, forming "one living filament".

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• Using fossil record as evidence

Evolution is a process of adaptation

Environment plays an active role in the evolution of organisms

Changes occur due to needs in the environment Not using a part = part goes

away Need a trait to survive = it

appears in next generation

this body builder’s offspring would be born buff.

Does this occur?

James Hutton and Charles Lyell were geologistswho studied fossils and rock layers and suggested that the Earth was much older (millions of years)!

…long enough for species to evolve gradually.

Lyell proposes geologic change was gradual and long

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A Scottish farmer and naturalist, is known as the founder of modern geology.

He was a great observer of the world around him. More importantly, he made carefully reasoned geological arguments.

He recognized that the history of the Earth could be determined by understanding how processes such as erosion and sedimentation work in the present day.

His ideas and approach to studying the Earth established geology as a proper science. 15

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• Lyell's version of geology came to be known as uniformitarianism, because of his fierce insistence that the processes that alter the Earth are uniform through time. Like Hutton, Lyell viewed the history of Earth as being vast and directionless. And the history of life was no different.

• Lyell crafted a powerful lens for viewing the history of the Earth. On Darwin's voyage aboard the Beagle, for example, he (Darwin) was able to decipher the history of the Canary Islands by applying Lyell's ideas to the volcanic rock he encountered there.

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The Clean Room

Season: 1 Episode: 7

http://www.cosmosontv.com/watch/230227523738

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Evolution Unit

http://www.youtube.com/watch?v=03YKT7ytJdE

http://www.youtube.com/watch?v=B4FVetapF2k

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Darwin was a British scientist who laid the foundations of the theory of evolution and transformed the way we think about the natural world.

On the voyage, Darwin read Lyell's 'Principles of Geology' which suggested that the fossils found in rocks were actually evidence of animals that had lived many thousands or millions of years ago.

Lyell's argument was reinforced in Darwin's own mind by the rich variety of animal life and the geological features he saw during his voyage.

Breakthrough in his ideas came in the Galapagos Islands, 500 miles west of South America. Darwin noticed that each island supported its own form of finch which were closely related but differed in important ways. 20

Charles Darwin

Joined the Crew of HMS Beagle in 1831

Naturalist: the idea or belief that

nothing exists beyond the natural world.

5 Year Voyage around world

Influenced by the ideas of Malthus, he proposed a theory of evolution occurring by the process of natural selection.

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Islands formed by hot magma reaching surface of crust

Older islands (4 million years old) are eroded and lower.

Newer islands (7000 years) are steeper

Darwin took a 5 year voyage 1831-1836

Darwin was struck by the variation (the difference in the physical traits) among individuals of the same or similar species.

Darwin realized that species may somehow be able to adapt to their surroundings.

An adaptation is a feature that allows an organism to better survive in its environment.

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Most important stop in voyage

Small group of volcanicislands 1000 km West of South America

Climates were basically the same, but . . .

The animals on islands were unique:

Tortoises IguanasFinches

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Island species varied from mainland species & from island-to-island species

Each island had long, medium or short neck tortoises: Necks were adapted

to food sources.

Tortoises with longer necks could reach the higher vegetation in drier areas, so they survived and reproduced, passing their long-necked genes to their offspring.

Tortoises in wetter areas had plenty to eat and didn’t need long necks to survive and reproduce.

Is an iguana found only on the Galápagos Islands that has the ability, unique among modern lizards, to live and forage in the sea, making it a marine reptile. The iguana can dive over 9 m (30 ft) into the water.

Finches on the islands resembled a mainland finch

More types of finches (and tortoises) appeared on the islands than the mainland where the available food was different: Seeds Nuts Berries Insects…

Finches had different types

of beaks adapted to their

type of food gathering

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Each island has slightly different weather:

lower islands are barren and dry,

higher islands are wetter

So, different islands have different vegetation, different habitat.

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Perhaps a few finches from the S. Am. mainland migrated to the new islands.

Over time their descendents were “modified” as different groups specialized in eating different foods.

http://pustakalaya.olenepal.org/wiki/images/94/9454.jpg

http://www.bio.miami.edu/~cmallery/150/evol/24x9.jpg

Darwin observed fossil evidence of species changing over time.

The fact that some fossils looked like living species suggested that modern animals might have some relationship to fossil forms.

These species NO longer existed.

Darwin wondered what had happened to them.

Glyptodon, a giant armadillo.

Giant ground sloth of South America

Some fossils looked like modern animals.

Giant Ground Sloth from Patagonia

Transform boundaries responsible for earthquakesConvergent plate boundaries push up mountainsDivergent boundaries also form volcanic islands (plates moving apart)

Darwin found marine fossils high in the mountains… How did they get there?

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Darwin also found fossil shells of marine organisms high up in the Andes mountains.

Darwin later experienced an earthquake during his voyage and saw firsthand the result: land that had been underwater was moved above sea level.

This helped explain why marine animals were found high up in the mountains.

Trilobite (marine animal)

Younger fossils lie above older fossils in undisturbed rock layers

Comparing fossils shows a gradual change from past to present life

We keep finding new fossils, but the fossil record will still have gaps

shows history of life over millions of years.

From looking at the fossil record, Darwin suggested that whales may have come from a 4-legged land mammal.

http://www.txtwriter.com/Backgrounders/graphics/evolution/page2a.jpg

Evolution Unit

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Darwin observed that domesticated species of plants and animals seemed to show variation in traits that were not shown in the wild relatives.

Natural Variation

There are “natural” differences and lots of variation among individuals of a species.

Artificial Selection

Humans selectively breed to enhance desired traits among stock or crops.

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This idea abandoned the theory that species were perfect & unchanging.

Farmers have used variation to improve crops & livestock for years.

The process by which humans change a species by breeding it for certain traits is called artificial selection.

In order for artificial – or natural - selection to occur, the trait must be heritable.

Heritability is the ability of a trait to be passed down from one generation to the next. 43

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When breeding livestock, humans choose the parents with traits they want in the offspring.

Ex: dogs, cows, horses, pigeons

Darwin used what he knew about artificial selection (human’s selecting useful traits for their own benefit) for his theory of natural selection: Mechanism by which individuals that have inherited

beneficial adaptations produce more offspring on average than do other individuals.

In nature, the environment is the selective agent.

Therefore, in nature, characteristics are selected only if they give advantages to individuals in the environment as it is right now.

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Malthus became widely known for his theories about change in population.

Malthus believed that unless people exercised restraint in the number of children they had, the inevitable shortfall of food in the face of spiraling population growth would doom mankind to a ceaseless struggle for existence.

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Darwin's thinking about the struggles for survival in the wild, where restraint is unknown. Before reading Malthus, Darwin had thought that living things reproduced just enough individuals to keep populations stable. He came to realize that, as in human society, populations bred

beyond their means, leaving survivors and losers in the effort to exist.

Darwin saw that the variation he had observed in wild populations would produce some individuals that were slightly better equipped to thrive and reproduce under the particular conditions at the time. Those individuals would tend to leave more offspring than their fellows, and over many generations their traits would come to dominate the population.

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Malthus’ Influence: Observed babies were being born faster than people

were dying. Office of Population Research, Princeton University

High birth rates & limited resources would force life & death competition War Famine Disease worked against growing populations

Population size was limited by resources such as the food supply

Each Species Struggles For: Food Living Space Mates

Malthus reasoned that if the

human population continued to

grow unchecked, sooner or later

there would be insufficient living

space & food for everyone.

Plants & animals produce far

more offspring than can be supported. Most will die

If they didn’t, the Earth would be overrun!

Death rate will increase to balance the population sizeand the limited food supply in the environment.

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Upon his return to England, Darwin developed his observations into the Theory of Evolution, but he did not publish for 25 years. . .

Darwin knew that his theory was extremely controversial and would be attacked.

His theory challenged both the established religious & scientific beliefs, particularly about the creation of man. 51

British naturalist, explorer, geographer, anthropologist, and biologist.

Best known for independently conceiving the theory of evolution through natural selection; his paper on the subject was jointly published with some of Charles Darwin's writings in 1858.

Explored the wildlife of South America and Asia.

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• Alfred Russell Wallaceindependently came to same conclusion as Darwin that species changed over time because of their struggle for existence.

• When Darwin read Wallace’s essay, he knew he had to publish his findings.

• Darwin made four main points in his book:• 1. overproduction• 2. variation• 3. selection• 4. adaptation 53

overproduction – while having many offspring raises the chance that some will survive, it also results in competition for resources

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variation – the differences that exist in every population (defined as all the individuals of a species that live in an area) are the basis for natural selection.

Differences result from characteristics inherited from parents or result from mutations.

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In a given environment, having a particular trait can make individuals more or less likely to survive and have successful offspring. So, some individuals leave more offspring than others do.

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Adaptation – sometimes a certain variation or trait allows an individual to survive better than other individuals it competes against in its environment.

More successful individuals are said to be more “fit.”

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An Inherited trait present in a population because it helps individuals survive AND reproduce in a given environment.

Individuals may have adaptations, but they DO NOT CREATE adaptations through use. (That’s Loser Lamarck!)

Fitness ability of an individual to survive &

reproduce

Individuals with low fitness die & produce few offspring

Adaptation inherited characteristic that

increases fitness (an organisms chance for survival)

Adaptations can be:

Physical

speed, camouflage, claws, etc.

Behavioral

solitary, herds, packs, activity, etc.59

Survival of the Fittest is also known as Natural Selection

It’s the driving force for evolution.

During the struggle for resources, the strongest will survive & reproduce.

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•The unequal ability of individuals to survive and reproduce leads to a gradual change in a population with favorable characteristics accumulating (building up) over generations. •New species evolve

Natural Selection

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Darwin proposed that organisms descended from common ancestors.

This implies all living organisms are related, that all organisms come from a single tree of life.

Idea states that organisms change with time.

These changes cause the evolution of new species.

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Species today look different from their ancestors.

Organisms have descended with changes from other species over time.

Natural selection acts on phenotypes, or physical traits, rather than on genetic material itself.

New alleles are not made by natural selection, they occur by genetic mutations.

Natural selection can act only on traits that already exist.

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Ex: Finches on the Galapagos Islands

Drought in 1977 reduced the amount of small soft seeds finches preferred.

Because large-beaked finches were able to crack the large, tough seeds, they did not starve.

The next year, there were a big increase of large-beaked hatchlings and most of the small beaked finches died. 65

Each type of finch occupies a different niche(ecological role) so competition is reduced.

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