1. Chapter 22 Darwinian Evolution

2. What is evolution ?
Descent with Modification
evolutionary change is based on the interactions between populations & their environment which results in adaptations (inherited characteristics) to increase fitness
Evolution
change over time in the genetic composition of a population.

3. Historical Context of Evolution
Darwin was influenced by many scientists in developing his theory.

4. Aristotle 384-322 B.C Species are fixed (unchanging)
Life-forms arranged of scale (ladder) of increasing complexity
(scala naturae)
Each life form had its permanent place on the ladder
Follows Old Testament (creationism)
Aristotle B.C

5. Classified diversity for the
Founder of taxonomy/binomial nomenclature
Domain – Kingdom – Phylum – Class – Order – Family - Genus – Species
Domains: Eubacteria, Archaea, Eukarya
Nested system: species grouped into increasingly general categories
Classification based on anatomy & morphology
Grouped species by resemblances from pattern of their creation not evolutionary relationships
Carolus Linnaeus
Classified diversity for the
“greater glory of God”

6. Paleontologist – studied fossils
Deeper strata (layers) - very different fossils from current life
Extinctions were common occurrences yet opposed idea of evolution
Catastrophism : events destroyed many living species in local areas, then area was repopulated by immigrant species
George Cuvier
( )

7. Geology Charles Lyell 1797-1875 James Hutton 1726-1797 Gradualism
Uniformitarianismmechanisms of change are slow and constant over time.
Slow & subtle changes in organisms lead to big change
James Hutton
Gradualism:
geologic change results from slow, gradual, continuous process still operating today.

8. Jean Lamarck (1744-1829) 1801 1. Theory of desire
- organisms change due to inborn desire to change to
become more fit for environment
ex: ant eaters develop long snouts
2. Theory of use and disuse
- organs that are being used get large and strong
- organs that are not used shrink and eventually disappear
ex: snakes- didn’t use legs so disappeared
3. Theory of inheritance
- acquired traits were passed on to offspring
ex: snakes that lost legs passed trait
Importance: Recognized that species evolve, although explanation was flawed

9. Malthusian Doctrine More babies born than deaths
Consequences of overproducing within environment: war, famine, disease
Struggle for existence
Thomas Malthus
( )

10. Charles Darwin ( )

11. British naturalist
Proposed the idea of evolution by natural selection
Collected clear evidence to support his ideas

12. Unique species

13. Darwin’s Finches Beak variation: an example of adaptive radiation.
14 species of finches: evolved from one common ancestor in South America

14. Darwin’s conclusions
small populations of original South American finches reached islands
variation in beaks enabled some to obtain food successfully in the different environments
over many generations, the populations of finches changed anatomically & behaviorally
accumulation of advantageous traits
emergence of different species

15. Finches with beak differences that allowed them to…
- successfully compete
- successfully feed
- successfully reproduce

16. Other examples of adaptations to food source

17. 1859: Origin of the Species
Darwin waited 30 years before he published his ideas on evolution
Alfred Russell Wallace – published paper on natural selection first (1858)
Charles Darwin (1859): On the Origin of Species by Means of Natural Selection Mechanism for evolution is Natural Selection Darwin didn’t use “evolution”, but rather “descent with modification”

18. Origin of the Species
Darwin amassed evidence that descent with modification by natural selection explains three broad observations about nature:
The unity of life: organisms share many characteristics
The diversity of life: organisms accumulate adaptations
The match between organisms and their environments

19. Darwin’s Theory of Natural Selection
Individuals that have physical or behavioral traits that
better suit their environment are more likely to survive
and will reproduce more successfully than those
without traits.

20. - organisms produce more offspring than can survive
Parts of Theory
1. Overproduction
- organisms produce more offspring than can survive
- leads to competition

21. 2. Genetic variation - individuals in a given species vary by chance (due to gene recombination) - normal . exception: identical twins

22. 3. Struggle to survive - all organisms face constant struggle to survive (limited resources)

23. 4. Survival of the fittest
- Individuals best adapted to environment are more likely to survive and reproduce
- Over time favorable traits increase in population
Adaptations enhance an organism’s ability to survive and reproduce.
Over long periods of time, steady input
of new variations in a population
lead to speciation.

24. DIFFERENCE IN THEORIES
Lamarck: organisms change in order to survive in environment
- occurs in the organism’s lifetime
Darwin: environment determines which organisms survive through natural selection
- occurs over many generations

25. Evidences of Evolution
Direct Observations
2. Fossil record
3. Homology
homologous & vestigial structures
embryology
molecular: protein & DNA sequence
4. Biogeograpy

26. 1. Direct Observations
Antibiotic Resistance: MRSA (methicillin-resistant Staphylococcus aureus)

27. Soapberry bug beak length shortened in response to change in food source.

28. 2. Fossil record
Most occur in layers of rock, with the youngest usually on top, and the oldest in deeper layers
(sedimentary rock)
Some found in amber (fossilized tree sap)
Record incomplete due to soft outer coverings on organisms not leaving imprints
99% of all species that lived on Earth are now extinct.

29. Transitional Species (links to modern species) Tiktaalik roseae, a 375 million-year-old transitional species between fish and the first legged animals, reveals that the evolution of hind legs actually began as enhanced hind fins.

30. 3. Homology (similarities among organisms)
Homologous structures: structures which developed from a common ancestor, but have changed over time due to different purposes (divergent evolution)

31. Embryologic similarities
evidence of a common ancestor
dorsal, hollow nerve cord, notochord (stiffening rod of cartilage) in the back
similar membranes in the embryos, yolk sac that produces the first blood cells and germ cells
similar development of many organs

32. Vestigial organs/ structures:
Structures which have lost all or most of their original function in a species through evolution.
Degenerated, atrophied, or rudimentary condition
Evidence of change over time
vestiges of pelvic girdle of eyes on nicitating membrane
leg bones of walking ancestors blind cave fish

33. Molecular/ Biochemical homologies
DNA, RNA, amino acids, and serology (comparison of blood chemistry)
Species
Amino Acid
Differences
from Human
Hemoglobin
Protein
Gorilla 1
Rhesus monkey 8
Mouse 27
Chicken 45
Frog 67
Lamprey
125

34. Evolutionary Trees
Closely related species (branches) share same line of descent until their divergence from a common ancestor
Homologous characteristics that are inherited from a common ancestor are strong indications of evolutionary relationships
For example, "Tetrapods" all possess four limbs, presumably because they evolved from an ancestor (#2) that had four limbs.
Pg 464

35. Convergent evolution
independent evolution of similar features in different lineages
Distantly reated species resemble one another
Analogous structures: similar in appearance and function, but different origins with different internal structures
- organisms with different ancestors become more alike because they share same environment
dissimilar structures  more similar structures

36. 4. Biogeography Geographic distribution of a species
Species in nearby geographic areas resemble each other
- Continental drift and Pangaea explains similarities on different continents
- Endemic species: found at a certain geographic location and nowhere else
ex: Marine iguanas in the Galapagos

37. Island Biogeography

38. Natural Selection vs Artificial Selection
Nature selects/decides
Man selects/decides
Acts on individual
Selective breeding
Population evolves over time
Inbreeding occurs
Occurs over long periods of time
Occurs in short period of time