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A present-day view of evolutionary theory
Vidyanand Nanjundiah
Centre for Human Genetics
Bangalore([email protected])
Indian National Science Academy, Delhi3 November 2014
The problem
To account for the presence on earth
of the highly improbable forms of matter
known as living creatures
http://cargocollective.com/turing/Belousov-Zhabotinsky-reactionand
http://www.metafysica.nl/dissipative_systems.html
http://www.pnas.org/content/107/20/9370.figures-only and http://www.veritas-ucsb.org/
The answers
1.Principles of physics and chemistry.
2.Chance.
Ahistorical: accidents whose outcomes persisted;‘random walk’
1.Natural selection.
Luidia sarsi (zygote develops into juvenile starfish with radial symmetry inside a larva with bilateral symmetry; Williamson & Vickers, Am Sci 95(6):509-517, 2007)
The answers
1.Principles of physics and chemistry.
2.Chance.
3.Natural selection.
Historical: accidents, advantageous outcomes;‘biased random walk’
Why does natural selection occur?
Because the individuals of a species are not all alike;
because they differ in their ability to survive and reproduce;
because they can pass on these traits to their children.
These are testable statements!
The essence of neo-Darwinian theory
1. Living organisms carry DNA or RNA sequences (genes) that can be copied inside a cell. The sequences differ from one individual to another.
2. Genes specify proteins.
3. Proteins ‘build’ bodies and confer various properties on organisms .
4. .Some individuals leave behind more children than others because they have different properties.
5. Then the protein composition of a population, and so also the genetic composition, changes in time.
Environmental pressure: relative, external
Genetic variation: random, internal
Response: systemic, internal
The signature of natural selection: Adaptation
(http://www.agen.ufl.edu/~chyn/age2062/lect/lect_11/18_20.GIF)
Heritable variation without genes: epigenetic inheritance
Ciliary row pattern in Tetrahymena (http://www.bioone.org/na101/home/literatum/publisher/bioone/journals/content/)
Egyptian plover and Nile crocodile (http://bookbuilder.cast.org/bookresources/12/12710/46346_1.jpg)
Co-evolution
Variation dependent on the environment: phenotypic plasticity
http://www.kyoto-su.ac.jp/english/department/graduate/g_eng/fm/kimura.html
Phenotypic plasticity(PANC-1 cells express FGF-2 (red) or FGF-2 receptor (green), but not both)
Hardikar et al. (2003) PNAS 100(12): 7117–7122
The signature of natural selection: Adaptation
Adaptation works only in the short term. Natural selection has no way of planning for the long term.