1. Descent with Modification: A Darwinian View of Life Ms. Day AP Biology
Evolution:
Descent with Modification: A Darwinian View of Life
Ms. Day
AP Biology

3. Darwin made two major points in his book called Origins of Species:
1. Many current species are descendants of ancestral species
2. Natural selection is a mechanism for this evolutionary process

4. Resistance to the Idea of Evolution
The Origin of Species = Darwin’s book
Shook the deepest roots of Western culture
Challenged a worldview that had been prevalent for centuries
Earth ONLY ~6000 yrs old
It was unchanging!!!!

5. Nature and Classification of Species
Greek philosopher Aristotle
organisms were perfectly formed and adapted to the world (fixed and unchanging)
Old Testament
Species individually designed by God and perfect
Carolus Linnaeus
Saw adaptations as evidence that a Creator had designed each species for a specific purpose
founder of taxonomy (biology concerned with classifying organisms) & binomial nomenclature (scientifically naming organisms- Genus species)

6. Fossils, Cuvier, and Catastrophism
The study of fossils helped to lay the groundwork for Darwin’s ideas
Fossils
remains or traces of organisms from the past, usually found in sedimentary rock, which appears in the layers or strata

7. developed by French scientist Georges Cuvier
Paleontology
study of fossils
developed by French scientist Georges Cuvier
Cuvier advocated catastrophism
species disappear due to a catastrophic event of earth’s crust (volcano, earthquake…)

8. Hutton’s Theory of Geological Change
Changes in Earth’s crust due to slow continuous processes
Idea Known as Gradualism

9. Charles Lyell Proposed theory of Uniformitarianism
Geological processes at uniform rates building & wearing down Earth’s crust
Proposed that the Earth was millions of years instead of a few thousand years old

10. Lamarck’s Theory of Evolution (1809)
Lamarck hypothesized species evolve through
use and disuse and
inheritance of acquired traits
The mechanisms he proposed are unsupported by evidence

11. Lamarck’s Theory of Evolution
Idea called Law of Use and Disuse
If a body part were used, it got stronger
If body part NOT used, it deteriorated

12. inheritance of acquired traits
Will his kids be born with big muscles because he has them?

13. WILL THE OFFSPRING BE NICELY PRUNED?

14. Principles of Populations
Thomas Malthus (1798)
Studied moths and natural selection
Capacity to over-reproduce is seen in all species
Eventually populations stop increasing in size and reach a steady state (carrying capacity)

15. Charles Darwin LOVED nature
Sails on HMS Beagle at 22 and voyaged around world
Noted flora and fauna on islands off of South America
Contributions of Lyell, Hutton and Malthus lead him to his mechanism for evolution
species change through natural selection

16. The Voyage of the Beagle
Collected specimens of South American plants and animals
Observed adaptations of plants and animals that inhabited many diverse environments
Main focus of geographic distribution of species = Galápagos Islands near the equator west of South America

17. The Galapagos Islands
Small group of islands 1000 km west of South America
Very different climates
Animals on islands unique

19. Darwin returned 5 years later in 1836
NORTH
AMERICA
SOUTH
AFRICA
EUROPE
AUSTRALIA
PACIFIC
OCEAN
ATLANTIC
England
Cape of
Good Hope
Cape Horn
Tierra del Fuego
Galápagos
Islands
Darwin in 1840,
after his return
HMS Beagle in port
Equator
Tasmania
New
Zealand
Andes
Darwin returned 5 years later in 1836

20. Darwin’s Focus on Adaptation
Adaptation= a change in structure or habits, often hereditary, to improve survival and reproduction in environment
Adaptation to environment and the origin of new species  are closely related processes
EXAMPLE
Finches on the islands resembled a mainland finch
Finches had different types of beaks adapted to their type of food gathering

21. LE 22-6
Cactus eater. The long, sharp beak of the cactus ground finch (Geospiza scandens) helps it tear and eat cactus flowers and pulp.
Seed eater. The large ground finch (Geospiza magnirostris) has a large beak adapted for cracking seeds that fall from plants to the ground.
Insect eater. The green warbler finch (Certhidea olivacea) used its narrow, pointed beak to grasp insects.

22. Darwin’s Overall Observations
Left unchecked, the # of organisms of each species will increase
In nature, populations tend to remain stable in size
Environmental resources are limited

23. More of Darwin’s Observations
Individuals of a population vary in characteristics with no 2 individuals being exactly alike.
Much of this variation between individuals is inheritable.

24. Darwin’s Overall Conclusions
Production of more individuals than can be supported by the environment leads to a struggle for existence among individuals
Only a fraction of offspring survive each generation
Survival of the Fittest

25. Darwin’s Conclusion
Individuals who inherit characteristics (adaptations) that are most fit (suitable/favorable) for their environment are likely to leave more offspring than less fit individuals
Called FITNESS
High survival = more offspring = more fit

26. Darwin’s Conclusion
Natural Selection
gradual, nonrandom process by which traits become more/less common in a population
Acts on PHENOTYPES (adaptations), which influences GENOTYPES
only organisms best adapted to environment tend to survive and transmit genetic traits to future generations while those less adapted tend to be eliminated
Key mechanism to evolution

27.
Video #4: How Does Evolution Really Work?

28. 1844
Darwin wrote an essay on natural selection but did not publish it
1858
Alfred Russell Wallace developed a similar theory of natural selection to Darwin’s (organisms evolve from common ancestors)
Darwin quickly finished The Origin of Species and published it the next year

29. Darwin’s Descent with Modification
refers to idea that all organisms are related through descent from common ancestor that lived in the remote past
the history of life is like a tree

30. Darwin’s 1st Idea: Evolution
What is evolution?
All accumulated changes across successive generations in inherited characteristics of populations
A change over time in the genetic combination in a population  give rise to diversity
Darwins definition = Descent with modification
Darwin’s 2nd Idea: Natural Selection
If an environment changes over time, natural selection may result in adaptation to these new conditions  new species can also evolve

31. What is Natural Selection?
Process by which individuals leave more offspring on average than do other individuals in the same population.
HOW?
An organism’s environment (habitat) favors certain adaptations (traits or behaviors) that allows the organism to better survive and reproduce  have better fitness

32. Natural Selection vs. Artificial Selection
Recall Natural selection
In artificial selection,
humans modify other species over many generations by selecting and breeding individuals with desired traits

35. What is a “theory” is science?
Scientific definition of theory is different from everyday meaning
non-scientific context of “theory” implies that something is unproven or speculative
Scientific definition refers to a comprehensive explanation of some aspect of nature that is supported by a vast (A LOT) body of evidence (data).

36. Is Evolution JUST a THEORY??? Is it SCIENCE based?
Video #1: Isn’t Evolution Just a Theory?

37. Evidence for Evolution http://www. sumanasinc
Homology
a similarities in characteristic traits resulting from common ancestry
Anatomical Homologies
anatomical resemblances that represent variations on a structural theme present in a common ancestor
Called HOMOLOGOUS STRUCTURES
Same development, different function

38. LE 22-14
Human
Cat
Whale
Bat

39. 3. Vestigial organs
remains of structures once important in organism’s ancestors
Example: tailbones in humans, appendix, wings on ostrich, wisdom teeth in humans

40. 4. Comparative Embryology

41. Similar genes (DNA), RNA or amino acid sequences
5. Molecular Homologies
Similar genes (DNA), RNA or amino acid sequences
Example
genes shared among organisms inherited from a common ancestor
Ex #1: Homeobox is a DNA sequence in genes that regular development in plants, animals and fungi

42. Human Rhesus monkey Mouse Chicken Ex #2: Amino Acid/ Frog
LE 22-16
% of Amino Acids That Are
Identical to the Amino Acids in a
Human Hemoglobin Polypeptide
Species
Human
100%
Rhesus monkey
95%
Mouse
87%
Chicken
69%
Ex #2: Amino Acid/
Protein sequence
Frog
54%
Lamprey
14%

43. 6. Biogeography the geographic distribution of species Sugar Glider
Marsupial
Flying
Squirrel
Eutherian
(placental)
Some similar mammals that have adapted to similar environments have evolved independently from different ancestors

44. 7. Genetic Changes over time
Bacteria becomes resistant to antibiotics

45. Paleontologists have discovered fossils of many transitional forms
7. Fossil Records
Paleontologists have discovered fossils of many transitional forms
Shows variety on organism across time

46. Some Cool Evolution Videos…
Poison Newts
Camouflage “Leaves”
Evolution of the Eye
Why Does Evolution Matter Now? (Video #6)