Understanding Evolution - Life goes on

“Life goes on!”
© Harshal Ganpatrao Hayatnagarkar
version 2014.05.05
CC BY-SA 3.0

 Why do we feel hungry?
 What keeps our body temperature around 98.6 ℉ or 37 ℃ ?
 Why our wounds are healed, by themselves?
 How does our body fight diseases?
 Why certain variety of wheat is more productive?
 Why certain computer software perform better than others, in
impossible situations?
 Are we alone in the Universe? Can there be Life elsewhere?
 …

Although not apparently so,
these questions are connected and so are their answers.
The thread connecting them is –
Theory of Evolution

What is
Evolution?
How to study
evolution?
History of Life
as Evolution
What next?Summary

 “History of changes”
 Passive process.
 NOT limited to biology.
 NOT synonymous to progress.
 NOT same as Origin of Life.
 Essentially interplay of variations over time.
 Explained by various theories (to be discussed later).

Origin of
Life
time
Evolution of Life
This presentation is about
Evolution of Life,
which starts
AFTER
Origin of Life.

Because
it is the study of history of Life,
the only known phenomenon in the Universe.

Medicines Food Climate Education
Technology Economics and
finance
Sociology Exobiology

“Nothing in biology makes sense except
in the light of evolution”
– Theodosius Dobzhansky
(Evolution) is a general postulate to which all theories, all
hypotheses, all systems must hence forward bow and
which they must satisfy in order to be thinkable and true.
Evolution is a light which illuminates all facts, a trajectory
which all lines of thought must follow — this is what
evolution is.
Why study evolution?

This is a long story, so behold !

Evolution
Diversity
Time
Implications
+ one needs tools and techniques to
study each of these aspects.

Evolution
Diversity
Time
Implications

To understand
so much diversity,
that once existed,
exists today, including the Humans
and
probably would emerge,
and to which
we are the witness.

 Literally means ‘Classification’ in Latin.
◦ Grouping organisms in different classes (lets
call them ‘buckets’ for simplicity).
◦ Well, putting buckets into bigger buckets.
◦ Deriving common properties for each
bucket.
 Linnaean Taxonomy
◦ Originally defined by Carolos Linnaeus in
1735.
◦ Based on morphology.
◦ Grouped organisms into groups and
subgroups.
◦ Organisms were created by God and Carolos
only classified and named them.

 Linnaean Nomenclature
◦ Binomial nomenclature
 Naming organisms by dichotomous key
 Meaning ‘two words’.
◦ [Genus species].
◦ For example
 Humans  Homo sapiens
 Elephant  Elephas maximu
 Potato  Solanum tuberosum
 Groups (we called them buckets earlier)
◦ Common features abstracted.
◦ Resulted in initial hierarchy.
 Final hierarchical definition
◦ With criteria
◦ E.g. Kingdoms
 Plantae, Animalia, Fungi.

abstract class Phylum extends Kingdom
abstract class Family extends Order
abstract class Genus extends Family
…
abstract class Homo extends Genus
class Homo_Sapiens extends Homo
harshal = new Homo_Sapiens(“Harshal”);
Only ‘Species’ can be
instantiated
*Java programming language

 Taxonomy has raised more questions than it
answered.
 Organisms are similar to one another…
◦ How much similar?
◦ Why those similarities?
◦ For example, fox is similar to wolf.
 As well as different…
◦ How much different?
◦ Why those differences?
◦ Fox is not wolf.

 In wrong buckets - Whales were fishes once.
◦ Classification based on appearances.
◦ And whale is NOT a fish, only if one looks INSIDE.

 In addition, there
are hints from the
development of
embryos of various
species.
 Tail at origin tells
tale of origin.

 Correction of such mistakes did not leave
taxonomy untouched of evolution, too.
 Taxonomy has itself been evolving since then.
Morphology Anatomy Physiology Microbiology
BiochemistryGenomicsProteomics
300
years of
journey

Linnaeus
1735
Haeckel
1866
Chatton
1937
Copeland
1956
Whittaker
1969
Woese et al.
1977
Woese et al.
1990
2
kingdoms
3 kingdoms
2
empires
4
kingdoms
5 kingdoms
6
kingdoms
3 domains
(not
treated))
Protista
Prokaryota Monera Monera
Eubacteria Bacteria
Archaebacteria Archaea
Eukaryota
Protista
Protista Protista
EukaryaVegetabilia Plantae
Fungi Fungi
Plantae Plantae Plantae
Animalia Animalia Animalia Animalia Animalia
Wikipedia:Taxonomy

If two objects are separating at rate of 1 inch per year
Then
After 1 million year, they would be 25.4 kilometers apart.

12 %
of
Geological
time
All major phyla.
First fishes.

 To give glimpse of events occurred in the
history of the Universe to fit into the scale a
common person can understand
◦ From Big Bang till today
◦ Thirteen billion years of the Universe’s history scaled
into 365 days of a year
 January 1st, 00:00:00 AM Big Bang
Each month is roughly
equivalent to a billion years
Prof. Carl
Sagan

But from such a remote past, what could survive to tell us the story?

 Literally means ‘Obtained by digging’ in Latin and
studied under ‘Paleontology’.
 A Fossil can be past impressions about the living
being (like a thumb impression).
◦ Impression of a leaf on a then-wet mud.
◦ An insect caught in a tree amber.
◦ Petrified skeletons of animals.
 All one gets from such an antiquity is a fossil. A
paleontologist must make sense out of them, such
as to ‘extract’, preserve, connect and date the
specimen.
 Fossils can still tell the story of the organism when
it was dying.
◦ Morphology
◦ Anatomy
◦ Physiology (possibly)

 Challenges
◦ Identifying if a specimen is a
fossil.
◦ Recovering a fossil as complete as
possible.
◦ Identifying parts and whole of a
fossil.
◦ Identifying organism of that fossil.
◦ Determining age of a fossil.
◦ Preserving for future study.

 Informally, an organism still alive
representing a lone species whose other
relatives are extinct.
◦ Coined by Charles Darwin himself.
◦ To understand certain anomalous species that have
survived evolutionary pressure for very long time.
 For example, platypus or duck-bill.

Lamarck’s
Theory
Darwin-
Wallace’s
Theory
Mendel's
Theory
Neo-
Darwinism
Modern
Evolutionary
Synthesis
 Theories have been evolving since last 200 years to
answer these questions

 ‘Inheritance of acquired
characteristics’
◦ For example, giraffes stretched
neck and passed it to progeny
generations after generations.
 It does not hold good today.
◦ There is no known reverse path
from phenotype to genotype.
Jean-Baptiste
Lamarck

 Explains origin of diversity over time i.e. Evolution
 Charles Darwin and Alfred Russell Wallace
◦ Independently and then together
◦ Popular as ‘Darwinism’ or ‘Survival of Fittest’
 Darwin influenced by Malthusian Catastrophe
◦ Human population tends to increase a lot faster than
food supply, which may lead to catastrophic
implications for entire planet.
Charles Darwin Alfred Russell
Wallace

Origin of species
Multiplication
Competition
Variation

Competition
Adaptation
SurvivalGrowth
Multiplication
Theory of
Natural
Selection
Speciation

To understand
Theory of Natural Selection,
we should understand
role of diversity and ecological niche.

 Kind of approximation of term
‘habitat’.
 Subset of Ecosystem.
 Hyperspace of multiple dimensions.
 Dimensions can be temperature,
Humidity, salinity, language and so
on.
 For example
◦ Salt water/fresh water.
◦ Arctic deep ocean water.
◦ Amazon rain forests.
◦ Highland forests.
◦ Top and bottom of Maple trees.
◦ Roof-tops in Manchester city.
◦ Marathi-speaking regions in India.
◦ Traffic signals in India .
◦ and almost anyplace where life-forms
exist.
Source: http://www.geol.umd.edu/~jmerck/GEOL388/lectures/06.html
Source:
http://hhh.gavilan.edu/rmorales/EcologySpring200
8.htm

 On Galapagos Islands Darwin observed variety
of finches, adapted for respective habitats.
◦ High altitude vegetation
◦ Highland forests
◦ Lowland forests
◦ Bushes
◦ Shoreline vegetation
 Even various levels of the same habitat, for
example, from top to bottom of tree trunk.
Source -
http://hhh.gavilan.edu/rmorales/EcologySpring2008.htm
Source - http://14yunhyu.wordpress.com/2013/08/31/d-2d-macroevolution/
Source: http://www.geol.umd.edu/~jmerck/GEOL388/lectures/06.html

 Species adapt to suit to their
habitat. Alternatively, only suitable
species survive in a habitat.
◦ Adaptation for food, safety, nursing
and so on.
 Competitive Exclusion Principle OR
Gause’s Law
◦ No two species can occupy the same
niche in the same environment for a
long time.
◦ “Complete competitors cannot coexist”.
◦ Thus if two organisms occupy exactly
same niche, then they are the same
species.
Source - http://hhh.gavilan.edu/rmorales/EcologySpring2008.htm
Source -
http://14yunhyu.wordpress.com/2013/08/31
/d-2d-macroevolution/

 Life forms are food for
others.
◦ Visually chains and
webs/networks.
◦ Mostly undiscovered.
◦ Delicate balance in
ecologies.
 Human interference.
◦ Try removing few species
here and there, the
ecological collapse may
happen (See Gaia
Hypothesis).
◦ For example, cell towers
and insecticides are killing
bees, reducing crop
output.
Source: http://en.wikipedia.org/wiki/File:Chesapeake_Waterbird_Food_Web.jpg

 Population/individual becomes better suited to
its habitat.
 Caused by variation through
◦ Mutation (random variation in genes)
◦ Breeding (sexual reproduction)
◦ Horizontal gene transfer (Asexual borrowing. Typically
occurs in bacteria).
 For example, in highland forests, those finches
will survive better which can crack nuts with hard
shells.

 Evolution of ecological and phenotypic
diversity within a rapidly multiplying
lineage.
◦ Starting with a recent ancestor, this process
results in an array of species with different traits
with which they can exploit a range of divergent
environments.
◦ For example, over generations few finches moved
up the tree and few moved down.
 Likely to trigger Evolutionary Radiation in
local ecosystem.
Source - http://14yunhyu.wordpress.com/2013/08/31/d-2d-
macroevolution/
Source -
http://hhh.gavilan.edu/rmorales/EcologySpring2008.htm

 Emergence of new species.
◦ Species : A group of organisms capable of interbreeding
and producing fertile offspring.
 Consistent variation passed to offspring.

 An increase in taxonomic diversity or morphological disparity, due to
adaptive change or the opening of ecospace.
◦ Essentially adaptive radiation spread across species.
◦ Essentially many branches in a phylogenic tree.
 Evolutionary Explosion
◦ A rapid radiation in a relatively short span of time.
◦ For example, Cambrian Explosion, The Internet.
 Cambrian Explosion
◦ Span of 10 million years happened 425 million years before.
◦ Blueprints of all known phyla emerged in this short span.

 Darwin postulated that species
change gradually and
continuously.
 However, Stephen Jay Gould
and others observed stasis and
sudden speciation, called as
‘Punctuated Equilibria’.
 Species ‘accumulate’ changes
and then ‘suddenly’ radiate
into new species.
 Introduced and reinforced idea
that species are Darwinian
individuals and not just
classes.
 Reasons are unknown. Source - http://en.wikipedia.org/wiki/File:Punctuated-equilibrium.svg

All these variations do not survive over time.
In fact,
99.9% of species
that have ever existed,
are now extinct,
including dinosaurs.

Predation Mating
Climate change
Externalities (such asteroid impact)

Job interviews
Marriages
Markets
Genetically Modified
Food/Organisms
&
Selective breeding
Conflicts and Wars

 Individuals survive because of useful variations
and perish because of harmful ones.
 Units of selection
◦ Self-reproducing molecules
◦ Genes
◦ Cells
◦ Individuals
◦ Groups
◦ Species
◦ Societies
◦ Nations

 Ecological contrasts
◦ Snow
◦ Black soot deposited on roof tops.
 Altered predator-prey pattern
◦ Black soot was getting accumulated on roof-tops, in all
seasons.
◦ White moths were becoming visible even during winter, on
accumulated black soot on roof-tops and predators could find
and eat them.
◦ Thus increasing black moths population over white ones.
Black moth Black mothWhite moth White moth
Black soot deposited by textile
factories
Snow deposited in winter
Black soot from textile
factories of Manchester

“Slow though the process of selection may be, if feeble man can do
much by his powers of artificial selection, I can see no limit to
the amount of change, to the beauty and infinite complexity of
the co-adaptations between all organic beings, one with another
and with their physical conditions of life, which may be effected
in the long course of time by nature's power of selection.”
Charles Darwin
Probably origin of term ‘Natural Selection’.

Source: http://en.wikipedia.org/wiki/File:Life_cycle_of_a_sexually_reproducing_organism.svg

 Fitness is NOT about being strong or healthy.
 “Ability to survive and to reproduce, both”
◦ Collective quality of a population of species.
◦ Also thought in terms of average contribution to ‘Gene
pool’.
◦ Simply, determines if a species would continue to
survive.

But what makes a baby elephant as strong as its parents?
OR
How traits are transferred from parents to children,
in general?

 Mendel’s Laws
◦ Law of Segregation
◦ Law of Independent Assortment.
 Discovery-rejection-rediscovery
◦ Work published in 1865-66.
◦ Initially rejected by scientific community of his time.
◦ Later rediscovered in 1900 independently by Hugo de Vries and
Carl Correns and was acknowledged.
 A set of primary tenets relating to the transmission of
hereditary characteristics from parent organisms to their
offspring;
◦ Units of heredity called as Factors
 Today known as Genes
 Basis of chromosomal inheritance and genetics.
Gregor Mendel

 Law of Segregation
◦ When any individual produces gametes, the copies
of a gene separate so that each gamete receives
only one copy.
 Law of Independent Assortment
◦ Alleles of different genes assort independently of
one another during gamete formation.
◦ Also known as "Inheritance Law"
◦ True only for ‘unrelated genes’

 Discovery of nucleic
acids DNA and RNA.
◦ Structure and role of
nucleic acids in
inheritance.
◦ Analogous to Mendel’s
work.
 Genes - Segments of
DNA and RNA.
◦ Functional units of
inheritance.
◦ For example, color of
eye/hairs.
James Watson Francis Creek

 What Mendel called ‘factors’ then, are called
as Allele today.
 Allele
◦ Either of a pair (or series) of alternative forms of a
gene that can occupy the same locus on a particular
chromosome and that control the same character;
◦ “Some alleles are dominant over others”

 Darwinism + Chromosomal
inheritance
 ‘Gene-centered view’ or
‘Selfish gene theory’
◦ Holds that evolution occurs
through the differential survival of
competing genes as if such genes
are selfish.
◦ Even further, altruistic behavior of
organisms are in fact
manifestations of selfish genes.
 Replicators
◦ Introduces concept of ‘replicator’
and two instances of them – Genes
and memes.
◦ What genes are for organisms,
memes are for cultures.

Phenotype
•Observable trait
•For example morphology, anatomy,
behavior and so on.
•Expression of genes
•Extended Phenotype
•For example bird’s nest.
•Extended expression of genes.
Genotype
•Genetic make-up
•For example, chromosomes, nucleotide
sequences in some cell organelles.
•Translates into phenotypes.
•Replication through extra-dimension of
time.

Amino acids Proteins
Nucleic acids
(RNA & DNA)
Chromosomes
and organelles
CellsTissuesOrgansIndividuals
Groups, herds,
societies and
nations
Ecosystem Planet

 Brings together fields that are separated
◦ From geology to paleontology.
◦ From molecular biology to ecology.
◦ From linguistics to political science.
 Neo-Darwinism becomes subset.
 It becomes possible to explain many
phenomena due to borrowed learning.

 Evolution = Study of
variation over time and
space
◦ Space  Variation across
individuals at any given time.
◦ Time  Variation across
individuals in past and
present.
 Systematics
◦ Study of the diversification of
life on the planet Earth, both
past and present, and the
relationships among living
things through time.
Evolution – A primer

 “The history of organismal evolution” 1
◦ Evolution is regarded as a branching process, [whereby
populations are altered over time and may speciate into separate branches, hybridize
together, or terminate by extinction]. This may be visualized as a
multidimensional character-space that a population
moves through over time.
 Basically family tree of species
 Further reading

Tree of Life
from
Phylogeny
point of view

1. Single entry for all the animals
No surprise that microbes account for more
than half biomass on Earth.
2. Common ancestor of animals
and fungi

Tree of Life (by David Hillis, based on genome sequences)
Explore more at
http://onezoom.org

Human Evolution Linux Evolution

 Variation - An individual is
different from others
◦ Of same kind – Attributes shared,
values differ.
◦ Of different kind – Attributes differ,
values differ.
 Classification
◦ One combines similar individuals
into a group, and then such groups
into larger groups and so on,
forming a hierarchy of groups
called Taxonomy.
◦ Shared attributes of groups in a
taxonomy
◦ In biology, species are loose
groups of similar, compatible
individuals, different from one
another.

Error in copying
information
Recombination
+
+
+
+
CreativityBorrowing/snatching
information
Mutation Horizontal transfer Sexual reproduction Creativity

Macroevolution
•Meteorology
•Economics
•Sociology
•Game theory
•Ecology
•Population genetics
•Behavioral science
Microevolution
•Anatomy
•Physiology
•Genetics
•Microbiology
•Chemistry
•Quantum mechanics
Individual

4. Growth
and
multiplication
•Mating
1. Variation
•Useful
•Harmful
2.
Competition
•In presence of
limited
resources
3. Selection
•Survival
1. Adaptation
2.
Radiation
3.
Speciation
Microevolution

Proteins
RNA
DNA
Structure and
behavior
Physiology
Cellular
Metabolism

 Study of changes that occur at or above the level of species, in contrast
with microevolution.
 For example, a new species emerges or a group of species goes extinct.
 Explosions and extinctions - Two recurring patterns in macroevolution .
Source: http://evolution.berkeley.edu/evolibrary/article/evoscales_01

 Extinction = Death of a species
◦ Extinction of species is continuous process.
◦ Sometimes, widespread and more destructive.
◦ Either due to evolutionary pressure or external events.
◦ Great evolutionary significance.
A B
C
D
E
D
i
v
e
r
s
i
t
y
Time (million years ago)
Major causes
Asteroid impact Volcano Fall in sea levels

(A) Ordovician-
Silurian
•450-440 Mya
(million years
ago)
•60-70% of all
species - 2nd
largest of all.
(B) Devonian-
Carboniferous
•375-360 Mya
•70% of all species.
•Extinction pulses
within this period.
(C) Permian-
Triassic
•250 Mya
•Deadliest of all,
Known as ‘Great
Dying’.
•Killed upto 95% of
all species.
•End of Trilobites,
arguably longest
surviving
organisms.
(D) Triassic-
Jurassic
•200 Mya
•Killed 70-75% of all
species.
(E) Cretecious-
Paleogene
•65 Mya
•Killed 75% species.
•Known for end of
dinosaurs.
A B
C
D
E
D
i
v
e
r
s
i
t
y
Time (million years ago)

It’s not all that bad…as in creative destruction, creation follows destruction.
Sometimes, more creatively…

 Rise in speciation in relatively smaller time window.
 Accelerated increase in diversity in geologically shorter
time.
 Usually, driven by rush to fill empty niches.
 It could be triggered by an innovative trait and sustained
by competition. For example development of –
◦ Photosynthesis.
◦ Oxygen-based metabolism.
◦ Aging.
◦ Sex.
◦ Eye.
◦ Endoskeleton and jaw.
◦ Endothermic mechanism.

 Approximately 540 million ago.
 All major animal phyla emerged from this period.
 Blueprints for all vertebrates including fishes, dinosaurs and humans.
 Triggered by –
◦ Invention of ‘eye’.
◦ Increase in oxygen levels.
◦ Snowball earth.
◦ Sustained by arms race thereafter.
 Rise of trilobites
◦ Arguably longest lived organisms till date – 300 million years.
◦ Highest inter-species diversity.

Cambrian explosion
•540 Mya.
•All major animal
phyla emerged from
this period
•Blueprints for
vertebrates
including humans.
•Triggered by –
•Innovation of ‘eye’.
•Increase in oxygen
levels.
•Snowball earth.
•Sustained by arms
race thereafter.
Devonian explosion
•440 Mya.
•First major adaptive
radiation of land-
based life such as
rise and spread of
free-spore vascular
plants.
•Rise of fishes, and
known as ‘age of
fishes’.
Triassic explosion
•240 Mya.
•After the largest
extinction event ‘P-
T’.
•Rise of dinosaurs.
•Rise of first true
mammals.
Paleogene explosion
•60 Mya.
•Adaptive radiation of
mammals, birds and
reptiles.

 When different organisms develop similar features to
survive in a common niche.
 For example, streamlined body for swimming swiftly in the
water.
Shark (Fish)
Whale (Mammal)
Penguin (Bird)
Dolphin (Mammal)
Kronosaurus (Reptile/dinosaur)

Okay, Evolution is a great story.
But, what if the tape is played again?

 For example (popular in sci-fi movies)
◦ Imagine you go on a jungle safari, albeit of Jurassic
age (150 Million years before present).
◦ You make a simply change, say killing a butterfly
and come back to present time.
◦ Should there be any impact of that killing on future?
◦ Alternative History.

 Small perturbation (at one place) may lead to large effects (at other
places).
 Observed by Edward Lorenz while modeling weather patterns that very
small changes in values (such as a flap of butterfly’s wings) lead to
dramatic changes in patterns (such as hurricane formation) over time.
Hence the name.
 For example , using wind speed of ‘10.0000001 Km/h’ instead of ‘10
Km/h’ may lead to vastly different predictions.
Edward Lorenz
time

 Chaos is NOT same as randomness.
 Randomness necessitates denial of any pattern or order.
 Whereas chaos is often termed as Hidden Order.
 “Extreme sensitivity to initial conditions”.
◦ Vastly different outcomes over time due to slightly different initial
conditions.
◦ Chaotic is property of all non-linear dynamical systems.
◦ Highlights significant path dependence.
◦ For example – Weather, Stock market crashes, Epidemics, etc.
 Always prevalent situation – any point in space-time is an initial
condition.
◦ Analogous to sliding rule, the window of study moves thus making any
point on rule as start of the window.
◦ Interesting part is about emergence of the other end of this window.

 Emergence = property or behavior of a
system demonstrated by none of its
individual parts but collectively by them.
◦ For example, intelligence is emergent property of
brain, made from zillions of neurons, though none
of them individually has this property.
◦ For example, locomotion is property of
automobile, but none of its parts.
 Natural selection makes it possible to
achieve similar goals with different routes.
◦ For example, due to convergent evolution, vision,
flight and streamlined body have been emerged in
different species in the past.
 Actually it may not matter in many cases
whether we play the tape once or many
times, due to phenomenon namely Self-
organization.
Changes in
Environment
Changes in
Population
Changes in
Individual

 A special kind of emergent phenomenon –
Spontaneous order arises out of local interactions of
components.
◦ For example, crystallization, galaxy formation, flocks of
birds, multicellular organisms, human societies and so on.
◦ Islands of predictability in the ocean of unpredictability.
 Perhaps, it’s an answer to every question regarding
Life, or at least participatory.
◦ Life is because of, is a and has self-organization.
◦ Natural selection itself is a kind of self-organization phenomenon.

Self-
organization
Chaos
Helps achieve similar results from different initial conditions.
Thus acts as opposite of chaos.

EvolutionVariations
Combinations
Populations
Competitions
Generations
Overview of Factors

Highlights some important
patterns in evolution
Functional integration
Functional differentiation
Complexity trend
Information aspect of evolution

From To Notes
Replicating molecules
"Populations" of molecules in
compartments
Can't observe
Independent replicators
(probably RNA)
Chromosomes RNA world hypothesis
RNA as both genes and
enzymes
DNA as genes; proteins as enzymes
Prokaryotes Eukaryotes Can observe
Asexual clones Sexual populations Evolution of sex
Protists
Multicellular organisms — animals,
plants, fungi
Evolution of
multicellularity
Solitary individuals Colonies with non-reproductive castes
Primate societies
Human societies with language, enabling
memes
Sociocultural evolution

 Increasing biocomplexity through Integration
 Smaller entities often have come about together to
form larger entities.
 For example Chromosomes, eukaryotes, sex
multicellular colonies.

 Often smaller entities
◦ Have become differentiated as part of a larger entity.
 For example DNA & protein, organelles, anisogamy, tissues,
castes and so on.
◦ Are unable to replicate in the absence of the larger entity.
◦ For example, organelles, tissues, castes and so on.
◦ Can sometimes disrupt the development of the larger
entity.
◦ For example, meiotic drive (selfish non-Mendelian genes),
parthenogenesis, cancers, coup d’état and so on.
 New ways of transmitting information have arisen.
◦ For example, DNA-protein, cell heredity, epigenesis,
universal grammar and so on.

 Complexity has been
rising since origin of
life.
 Cambrian Explosion
◦ A tipping point.
◦ Accelerated pace of
increase in complexity.
◦ A pattern in evolution,
typically preceded by
an extinction
event/span.

 Quasi-closed system/habitat,
populations of species affect
each other.
 In predator-prey model, changes
in demand and supply.
 Complex relationship in
presence of multiple predator
and prey species.
 Such patterns affect
environment.
◦ For example, if a grass consumed
by rabbits will affect population of
not only rabbits, but also wolfs.

Bacteria Herb
Rabbit
Wolf
Single mutation in a bacterium
can significantly affect an herb,
which forms significant diet of a species like rabbit
and thus affecting population of wolves too,
that feed upon rabbits.

 Life forms are food for
others.
◦ Visually chains and
webs/networks.
◦ Mostly undiscovered.
◦ Delicate balance in
ecologies.
 Human interference.
◦ Try removing few species
here and there, the
ecological collapse may
happen (See Gaia
Hypothesis).
◦ For example, cellphone
towers and insecticides are
killing bees, reducing crop
output.
Source: http://en.wikipedia.org/wiki/File:Chesapeake_Waterbird_Food_Web.jpg

 Biosphere is a self-regulating
entity.
 “Abiota affects biota and vice
versa”.
 Cycles in a Daisy World.
 Model for climate change.
Prof. James
Lovelock

 Now a fact instead of fiction.
 Major contribution by humans.
◦ By Gaia hypothesis, climate change in turn will affect humans.
◦ Rise in ocean levels, resulting into submerging of coastal cities.
◦ Frequent hurricanes and cyclones.
 Changes in seasons to affect
◦ Harvest - ‘Malthusian catastrophe’.
◦ Ecology – Book ‘Collapse – How societies choose to succeed or fail’.
 However, humans will affect humans too.
◦ ‘Behavioral sink’

 “A condition or event by which a population
returns to subsistence level conditions once
population growth outpaces agricultural growth”
– Wikipedia
◦ An Essay on the Principle of Population published in
1798.
◦ Inspired Charles Darwin, to late discover Theory of
Origin of Species.
 Criticism
◦ New knowledge and technology can avert such crisis.
For example, Green Revolution.
◦ Socio-economic aspects such as birth control and
urbanization play their role too.
Thomas
Malthus

 Increasing population
has its impact on itself
too.
 An experiment to
understand impact of
overpopulation.
◦ From 1947 to 1972.
◦ Published initial result in
Scientific American in
1968.
◦ Though experiment
involved rats, results are
indicative to humans too.
John B. Calhoun

 Many rats placed in a relatively small
area.
◦ Area divided into four rooms, with
decreasing amenities such as food, water
and protection.
◦ Rats in each room showed different
behavior.
 Least resourceful room was termed as
Behavioral Sink.
◦ Rats showed destructive behavior,
especially towards weaker rats such as
females and babies.
◦ It resulted into inability of females to carry
through pregnancy and mortality rates as
high as 96 percent.
 Similar indicative behavior can be seen
in patches of human societies too.

 Economy crisis
◦ Faltering growth.
◦ Booming and busting bubbles.
◦ Unemployment.
◦ Inequality.
 Energy crisis
◦ Depleting fossil fuel sources.
◦ No viable alternative in sight.
 Ecology crisis
◦ Mining, petroleum and heavy industries.
◦ Automobiles and livestock.
◦ Shrinking fisheries, forests, glaciers and
icecaps.
Humanity
Crisis
Ecology
crisis
Economy
crisis
Energy
crisis

Evolution has brought us here.
It will guide us from here.

 Evolution is interplay of scale and diversity
over time.
 Change is the only constant thing.
◦ Hence evolution is omnipresent and almighty.
 Never underestimate power of small change.
◦ Butterfly effect
◦ An action sets the Universe on a new course, every
time and all the time.
(“Everything else is an illusion” – Bhagvadgeeta)

 Prof. N Swaminathan and other colleagues.
AND

To be continued with
Evolution: Understanding facts
Being evolutionary is not a bad idea,
perhaps because
being survived as fittest is not a bad idea too.

Understanding Evolution - Life goes on

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