a present-day view of evolutionary theory vidyanand nanjundiah centre for human genetics bangalore...
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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://www-images.warwick.ac.uk/about/environment/faqs/biodiversity.jpg)
Living Matter
Clue: the forms of living matter are interrelated
Principle of
continuity
Vertebrate forelimbs
http://home.comcast.net/~mkent595/circum1.gif
The answers
1.Principles of physics and chemistry.
2.Chance.
3.Natural selection.
The answers
1.Principles of physics and chemistry.
Ahistorical
1.Chance.
2.Natural selection.
D’Arcy Thompson, “On Growth and Form”
http://cargocollective.com/turing/Belousov-Zhabotinsky-reactionand
http://www.metafysica.nl/dissipative_systems.html
http://www.wired.com/2011/02/turing-patterns/
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.
http://www.biomedcentral.com/1741-7007/8/45/figure/F1
(cytochrome C) http://fishgenomes.blogspot.in/2011/03/workshop-on-molecular-evolution-north.html
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’
Darwin, 1840
Alfred Russel Wallace (1823-1913)
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!
Genes and Organisms
Genes Proteins Organelles Cells
Tissues Organisms
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
We cannot run faster than him!
I don't want to run faster than him; I want to run faster than YOU !
The signature of natural selection: Adaptation
(http://www.agen.ufl.edu/~chyn/age2062/lect/lect_11/18_20.GIF)
Does the neo-Darwinian framework
require modification?
Do many roads lead to Rome?
Heritable variation without genes: epigenetic inheritance
Ciliary row pattern in Tetrahymena (http://www.bioone.org/na101/home/literatum/publisher/bioone/journals/content/)
Environment created by organism:Niche construction
snailstales.blogspot.com
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
Environment-induced modification
Daphnia; https://wiki.cgb.indiana.edu/display/DGC/Projects
Self-organisation
R. Blanton
Scope of evolutionary thinking:
1. Mathematics
2. History
3. Culture
4. Behaviour
5. Psychology
What next?
Echinoidea; Van Valen, L. 1973. Evol. Theory 1: 1-30.
Summing up
Following slides ‘extras’, to be used only if the subject crops up during question time
What next?
The brain
Evolution is also concerned with dead matter
Vertebrate forelimbs
http://home.comcast.net/~mkent595/circum1.gif
‘Plasticity’
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
Spontaneous self-organisation
Life cycle of slime mould
Reproduction
“1 1+1”
“1 1/2”
Asexual reproduction (mitosis): 11+1
Sexual reproduction (meiosis): 11/2
Molecular biology applied toevolutionary questions
Behaviour too has evolved
www.animals.howstuffworks.com
The nerve cell
Natural selection can be compared to climbing
Getting to the next peak involves crossing a valley
OK, I'll try to divert him. And you'll see, my genes can spread better than yours!
The signature of natural selection: Adaptation
Adaptation works only in the short term. Natural selection has no way of planning for the long term.
Natural selection
Natural selection depends on particular properties of living matter:
Variation
Almost faithful reproduction
Differences in ability to survive and reproduce