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Chapter 16 Darwin’s Theory of Evolution

Unit 4 Evolution and Behavior

Chapter 16 Darwin’s Theory of Evolution

Ch 16.1 Darwin’s Voyage of Discovery

  1. What was Charles Darwin’s contribution to science?
  2. What three patterns of biodiversity did Darwin note?

Objective 1:  What was Charles Darwin’s contribution to science?

Darwin developed a scientific theory of biological evolution that explains how modern organisms evolved over long periods of time through descent of common ancestors.

Objective 2:  What three patterns of biodiversity did Darwin note?

1.  Species varied Globally

Darwin observed emus, ostriches, and rheas living in the grasslands of Australia, Africa, and So America.

  • How are the birds similar?

Darwin noted that different, yet ecologically similar, animal species inhabited separated, but ecologically similar, habitats around the globe.

Darwin began to wonder…

  • Why were the large flightless birds only found in the Southern Hemisphere?
  • Why were rabbits that lived in the grasslands of Europe not found in Australia but kangaroos were?

2.  Species varied Locally

Darwin noticed that there were two species of rheas in So America.  One in Argentina’s grassland and one further to the south.

http://www.birdlife.org/datazone/speciesfactsheet.php?id=3

http://animals.nationalgeographic.com/animals/birds/greater-rhea/

  • Why night there be two different species?
  • How might they differ?

Video:

3.  Species varied Over Time

Darwin collected fossils as well as observing living organisms.

Review:

  • What is a fossil?
  • What two conditions are necessary for fossilization?

armdillo vs glypt

See page 453 comparing an armadillo to a glyptodont

 

 

 

 

 

Review Video:

Ch 16.2 Ideas That Shaped Darwin’s Thinking

Objectives:

  • 1.  What did Hutton and Lyell conclude about Earth’s history?
  • 2.  How did Lamarck propose that species evolve?
  • 3.  What was Malthus’s view of population growth?
  • 4.  How is inherited variation used in artificial selection?

Objective 1:  What did Hutton and Lyell conclude about Earth’s history?  page 454

  • Hutton and Lyell concluded that Earth is extremely old and that the processes that changed Earth in the past are the same processes that operate in the present.
  • Hutton proposed the idea of “deep time” meaning that Earth’s history is so long that it is difficult for humans to understand.
  • Darwin read Lyell’s books while on the voyage of the Beagle.  They helped him explain the following event he witnessed is So America.
  • What law or principle did Lyell prop0se that is summarized by “the present is the key to the past”?
  • Darwin witnessed and earth quake in So America.  The force was so great that it threw him on the ground and lifted a stretch of rocky shoreline 3 meters out of the sea.  The section of shoreline had mussels and other sea creatures clinging to it.
  • Later, Darwin observed fossils of sea creatures in mountains high above sea level.  How might marine fossils have gotten to the tops of the mountains?
  • Darwin reckoned- If Earth can change over time, could life?

Objective 2:  How did Lamarck propose that species evolve? page 456

Lamarck suggested that organisms could change during their life times by selectively using or not using various parts of their bodies.  He also suggested that individuals could pass these acquired traits on to their offspring, enabling species to change over time.

LamarckReview Video:

Science in seconds 1:55

https://www.youtube.com/watch?v=4HBdxDBqfHc

Objective 3:  What was Malthus’s view of population growth?

  • Malthus reasoned that if the human population grew unchecked, there wouldn’t be enough living space and food everywhere
  • What forces could work against human population growth?
  • Darwin applied Malthus’s reasoning to other living organisms.

Oysters produce millions of eggs each year.

  1. Do all the offspring survive?
  2. What would happen if all the offspring survived?
  3. What determines which offspring survive?

 

Objective 4:  How is inherited variation used in artificial selection?

To find an explanation for change in the natural world, Darwin studied how organisms changed in the domesticated world.

Darwin noticed that farmers had developed “breeds” of livestock by crossing individuals with desired traits.  Over time, livestock had become specialized ie.  Some breeds of cattle were milk cows while others were better producers of meat.

 

red angusmilk cow

Compare 4 types of Belgian sheepdogs

http://cdn-0.dooziedog.com/dog_breeds/laekenois/images/full/4-Types-Belgian-Sheepdogs.jpg

Compare types of cats

16.3 Darwin Presents His Case

Objectives:

  1. Under what conditions does natural selection occur?
  2. What does Darwin’s mechanism for evolution suggest about living and extinct species?

1.  Under what conditions does natural selection occur?

Natural Selection occurs in any situation in which

  • more individuals are born than can survive (the struggle for existence)
  • there is heritable variation
  • there is variable fitness in the individuals (survival of the fittest)

2.  What does Darwin’s mechanism for evolution suggest about living and extinct species?

Natural selection depends on the ability of an organism to survive and to reproduce.  Every organism is alive today because they are descended from their parents who survived and reproduced.

The more fit the organism, the longer the organism will survive and the more offspring they will produce.

Organisms with certain traits were more “fit” to survive specific situations ie.  in your lab, green walking sticks survived better than red walking sticks when hiding i n the bush.

Over time, what happened to the population of the green walking stick?

Over time, what happened to the population of the red walking stick?

Darwin thought he walking sticks were modified over time and eventually the population of walking sticks was all green.  Since the population came from the same ancestors, Darwin called this descent with modification.

This led

 

 

Lab Links:

  • Part 1:  Walkingstick predation:  Bush EnvironmentWalking sticks Link

http://www.fossweb.com/delegate/ssi-foss-ucm/Contribution%20Folders/FOSS/multimedia_ms_1E/PopulationsandEcosystems/menu.html

  • Part 2:  Comic Book Crickets
  • Sneaky crickets

http://evolution.berkeley.edu/evolibrary/article/sneakermales_01

  • Part 3:  Evidence reading
    Read the passage to answer the questions

http://bioweb.cs.earlham.edu/9-12/evolution/HTML/live.html

Review Video:

Clearly stated:  What is Natural selection? 9:18

https://www.youtube.com/watch?v=0SCjhI86grU

Bozeman Science 10:16

https://www.youtube.com/watch?v=R6La6_kIr9g

Crash Course Biology # 14:  Natural Selection 12:43

https://www.youtube.com/watch?v=aTftyFboC_M

16.4 Evidence of Evolution

Darwin’s theory relied on assumptions from many fields of science:

geology, physics, paleontology, chemistry, and embryology

Objective:

Be able to explain the 5 areas of evidence for Darwin’s Theory

  1.  Biogeography
  2. Age of the Earth and Fossils
  3. Comparing Anatomy and Embryology
  4. Genetics and Molecular Biology
  5. Testing Natural Selection

1.  Biogeography

Objective:  How does geographic distribution of species today relate to their evolutionary history?

Biogeography is the study of where organisms live now and where their ancestors lived in the past.

Patterns in the distribution of living and fossil species tell us how modern organisms evolved from their ancestors.

Closely related but different

Biogeography suggested to Darwin that the turtles descended from a common ancestor but, over time through natural selection, variations in populations resulted in different species adapted to the conditions of each island.

Distantly related but similar

Similar habitats around the world favored similar adaptations.  Differences in body structure showed the organisms evolved from different ancestors.  Similarities in the organisms showed similar selective pressures favored similar adaptations.

2.  The Age of the Earth and Fossils

Objective:  How do fossils help to document the descent of modern species from ancient ancestors?

Age of the Earth

  • Evolution takes a very long time
  • For Darwin’s idea of evolution to be true, the Earth had to be very old.  Hutton and Lyell argued that the Earth was very old but did not have the technology to prove it.

Recent Fossil Finds

The Earth is dynamic.  This disrupts the geologic record.  Darwin did not have a complete fossil record to show the progression from an extinct organism, through its intermediate ancestors, to today’s extant organism.

 

3.  Comparing Anatomy and Embryology

Objective:  What do homologous structures and similarities in embryonic development suggest about the process of evolutionary change?

Homologous Structures

  • The same structure but different function due to descent with modification.  This suggests a common ancestor.  Example:  the front leg of a cat and pigeon wing

Analogous Structures

  • Body parts that have the same function but different structure.  Example:  bird wing and butterfly wing.

Vestigial Organ

  • A structure that is inherited from an ancestor that has lost much or all function.  Example:  appendix

Embryology

  • Similar patterns in embryo development provide further evidence of a common ancestor.

4.  Genetics and Molecular Biology

Darwin’s most troublesome “missing information” had to do with heredity.  With the work of Watson and Crick, genetics has supplied some of the strongest evidence of evolution.

The universal genetic code DNA = A G T C codes for amino acids which in turn make proteins.

Scientists can now compare the genetic code of organisms and look for relatedness on  a microscopic level.

5.  Testing Natural Selection

The work of the Grants comparing beaks of finches on the Galapagos Islands.

On initial visits, there was not a marked difference in the variation of beaks from year to year.  Following a drought year, the population of large beaked finches increased, while the population of small beaked finches decreased.  The large beaks were more fit (survival of the fittest) in drought conditions.  Therefore, more large beaked finches survived and produced more offspring.

Review Videos:

Clearly Stated Evidence for Evolution:  11:21

mhttps://www.youtube.com/watch?v=lIEoO5KdPvg

How Evolution works 11:47

https://www.youtube.com/watch?v=hOfRN0KihOU

Ch 17 Evolution of Populations