1. Darwin
Chapter 22

2. Charles Darwin Lived in England 1809-1882
: Beagle’s five-year voyage mapping the coastline of South America
1859: On the Origin of Species by Means of Natural Selection
EVOLUTION  explains how modern organisms evolved over long periods of time through descent from common ancestors 

3. On the Origin of Species by means of Natural Selection
Published by Darwin in (158 years ago)
Two major claims:
The species present on Earth today descended from ancestral species
Natural selection is the mechanism for evolution
Natural Selection leads to evolutionary adaptation.
Individuals with beneficial heritable traits leave more offspring, therefore, the frequency of those traits increases in the population over generation
Evolution – changes in a population’s genetic composition over time.

4. Darwin challenged traditional views
Prevailing view = Earth was only a few thousand years old, species of organisms were unchanging, created by God

5. Historical context
Aristotle ( B.C.) – all living forms could be arranged on a scale of increasing complexity = scala naturae
species are permanent and perfect and do not evolve
Natural Theology – 1700s
Based on Old Testament creation story
Species were individually designed by God and do not evolve
Taxonomy = science of classification
Sought to classify the species that God had created
Linnaeus ( ) – taxonomy showed God’s organization

6. Historical context (continued)
Georges Cuvier ( ): paleontologist; felt changes in fossils at different strata due to catastrophism.
Some catastrophe (flood or drought) destroyed large numbers of species at a time
Hutton: ( ): gradualism; profound change can take place through the cumulative effect of slow but continuous processes.
Earth’s geologic features explained by mechanisms currently operating in the world.

7. Historical context (continued)
Charles Lyell ( ): uniformitarianism; basic geological processes (wind, rain, erosion, etc.) have not changed throughout Earth’s history.
Darwin reasoned that Earth must be older than 6000 years

8. Other scientists suggest that evolution occurs
Lamarck’s theory of evolution: theory of evolution based on the idea that modification acquired during life of an organism passed to offspring.
Wallace: also developed theory of evolution based on natural selection in1858; this pushed Darwin to publish his findings

9. Acquired Characteristics Inherited Characteristics
List the characteristics that you believe you have always had. For example, you may have brown eyes or curly hair.
List your acquired characteristics. For example, you may have learned how to play a musical instrument.

10. Lamarck’s Evolutionary Hypothesis
Jean Baptiste Lamarck – proposed theory of evolution based on growing fossil record
Suggested that organisms could change during their lifetimes by selectively using or not using various parts of their bodies.
Suggested that individuals could pass these acquired traits onto offspring, enabling species to change over time
Published ideas in 1809 – year Darwin was born
Lamarck proposed that all organisms have an inborn urge to become more complex and perfect, and to change and acquire features that help them live more successfully in their environments.
Lamarck thought that organisms could change the size or shape of their organs by using their bodies in new ways.
Traits altered by an individual organism during its life are called acquired characteristics. .

11. Evaluating Lamarck’s Hypothesis
Lamarck was INCORRECT because:
Organisms do not have an inborn drive to be perfect
Evolution does not mean that over time species becomes “better” somehow
Evolution does not progress in predetermined direction
Traits acquired by organisms during lifetime cannot be passed on to offspring
Lamarck gave us some good stuff too!
Lamarck was one of 1st to try to explain evolution scientifically using natural processes
Recognized link b/w org’s environment and body structures

13. Darwin’s research Charles Darwin (1809-1882)
Voyage of the HMS Beagle – 1831
mission to chart the South American coastline
Observations:
Adaptations of plants and animals were similar in similar environments
Geologic change (for example due to earthquake) indicated that Earth was much older than 6000 years.
Geographic distribution of unusual species on Galapagos indicated descent with modification

14. Blue Footed Boobies

15. Artificial Selection
Artificial Selection: selective breeding of domesticated plants and animals to produce offspring with genetic traits that humans value
nature provides variation, humans select variations that are useful.
Example: a farmer breeds only his best livestock

16. Artificial Selection
Humans have been modifying species for thousands of years
Darwin saw this being done with dogs
He observed that a species could be changed a lot in a short period of time
Thought that the same thing could be happening in nature at a slower pace

17. Differences Natural Selection Artificial Selection
Traits that are more beneficial in the organisms environment become more common in the population
Humans choose the traits that become more common in the population

18. What Darwin Knew What did Darwin (and science) know?
The Earth is REALLY old
4.6 Billion Years
The Earth has changed over time
Mountains and valleys formed
Rivers change course
Water erodes land
Humans can change organisms through breeding
Organisms have rapid Population Growth
Darwin realized most organisms don’t survive and reproduce…
???Which individuals survive and why???

19. What Darwin didn’t know
DNA and Genetics
Knew that traits were passed from parent to offspring
Didn’t know HOW

20. POGIL

21. Struggle for Existence
If more individuals are produced than can survive  members of a population must compete to obtain food, living space, and other limited necessities of life
Called: Struggle for Existence
Which individuals come out on top of struggle?

22. Variation and Adaptation
Individuals have natural variations among heritable traits
Some variants are better suited to life in their environment than others
Predatory species that are faster, longer claws, sharper teeth  catch more prey
Prey species that are faster, better camouflaged  avoid being caught

23. Some Variations are Favorable
Adaptation - any heritable characteristic that increases an organism’s ability to survive and reproduce
Body parts or structures
bear’s claws
body color  camouflage or mimicry
Physiological functions
a plant carrying out photosynthesis
Behaviors
avoidance strategies prey use
crane flapping wings

24. Darwin’s Theory of Natural Selection
Animals on different islands are in different populations
Galapagos Islands were most likely colonized by a single finch species from South America
Single species adapted to the varied habitats on the islands
Today we have 13 different species of finch
Differ by Beak Shape
WHY?

25. Darwin’s Observations
Overproduction
Variation
Based on Malthus’ Idea, Darwin realized that species tend to produce excess offspring
limit resources + excess offspring = competition
Not Everyone Survives!
Differences among members of the same species
Most variation is heritable
Siblings look more like each other than they do other people

26. Darwin’s Observations

30. Natural Selection and Species Fitness
Overtime, natural selection results in changes in the inherited characteristics of a population.
These changes increase a species fitness
survival rate

31. Summary of Darwin’s Theory The Process
Organisms differ; variation is inherited
Organisms produce more offspring than survive
Organisms compete for resources
Organisms with advantages survive to pass those advantages to their children
Species alive today are descended with modifications from common ancestors

32. Summary of Darwin’s ideas
Natural selection refers to the differential success in reproduction which results in adaptations of populations of organisms to their environment
Natural selection occurs from the interaction between the environment and the inherent variability in a population
Variations in a population arise by chance
Natural selection is not a chance phenomenon, since environmental factors set definite criteria for reproductive success