The document discusses the evolution of life through various mechanisms like natural selection, genetic drift, and mutation. It explains different levels of evolution from population genetics to speciation and provides evidence of evolution through fossils, homologous organs, and orthologous genes. The document also covers applications of evolutionary biology in genomics for understanding disease, conservation efforts, and tracing human ancestry.

1. Evolution of life
Dr.Ranajit Das
Assitant Professor
MCNS, MAHE
Science Week, 2019

2. (Metabolism)
(Reproduction)
(Evolution)
(Homeostasis)
(Distinct organization and
compartmentalization)

3. Tree of life
Three domain system of classification (1977)
Eukaryote tree of life

4. Origin of MetazoansMetazoan Diversity

6. some common misconceptions about
Evolution
“You can't even begin to understand biology, you can't understand
life, unless you understand what it's all there for, how it arose - and
that means evolution”.
- Richard Dawkins

7. Evolution is NOT a theory: it can be proved experimentally
Evolutionary constraint

8. The evolution ‘controversy’
irreducible complexity
(IC): Some biochemical
structures are too
complex to be
explained by known
evolutionary
mechanisms and are
therefore result of
intelligent design.

9. Definition of Evolution
• Classical definition: Descent with
modification
• In terms of Population genetics: Change
in allele frequency in the subsequent
generations
• Evolution can be both micro (population
genetics) and macro (phylogenetics)

10. 25.1
EVOLUTION
is
Change through time
is
is
due to due to
does not produce
Changes in allele frequencies
Descent with modification
due to
Inbreeding
• Mating among
relatives
• Changes
genotype
frequencies,
but not allele
frequencies
Sexual selection
25.6 25.6
• Occurs when
traits used in
attracting
mates vary,
and individuals
with certain
traits attract
the most
mates
includes
includes includes
NATURAL SELECTION
• Occurs when traits vary,
and individuals with
certain traits produce
the most offspring
24.1
24.3–5
25.2
exposes
deleterious
alleles to
Non-random mating
25.6
Text section where
you can find more
information
is the only
evolutionary
mechanism that
can produce
Adaptation
• Involves heritable
traits only
24.3, 24.5
Fitness
• Measured by number of
offspring produced
24.3,
24.5
25.1–6
usually
reduces
due to
25.3
GENETIC DRIFT
• Changes in allele frequencies
due entirely to chance
• Especially important in small
populations
due to due to
MUTATION
• Random changes in DNA
• Creates new alleles
• Occurs in every individual in
every generation, at low
frequency
15.4, 25.5
GENE FLOW
• Occurs when individuals move
between populations
• Homogenizes allele frequencies
between populations
Gene
flow 25.4
due to lack of
produces divergence required for
produces
divergence
required for
produces divergence required for
26.2–4
SPECIATION
Results from:
1. Genetic isolation, followed by
2. Genetic divergence
creates new branches on
form smallest possible tips on
The TREE OF LIFE
• Describes the
evolutionary
relationships
among species
1.3, 27.1
“prune”
MASS EXTINCTIONS
• 60% of species are lost in less
than 1 million years
• 5 events in the past 542 million
years
• Is analogous to genetic drift
27.4
may occur after
forms new
26.1
Species
Evolutionarily independent units
in nature, identified by:
1. Reproductive isolation, and/or
2. Phylogenetic analysis, and/or
3. Morphological differences
with
Synamorphies
• Traits that are unique to a single
lineage (found in some species
but not others)
• Arise in a common ancestor
26.1
27.1
that
may
be
Key innovations
• Traits that allow
species to exploit
resources in a
new way or use
new habitats
27.4
may
result
in
ADAPTIVE RADIATIONS
• Rapid and extensive speciation
in a single lineage
• Dramatic divergence in
morphology or behavior
(species use a wide array of
resources/habitats)
27.3

11. Evidence of Evolution
Fossils
Homologous organs
Ontogeny repeats phylogeny
Orthlogous genes

12. Homology vs. Homoplasy

13. Convergent evolution due to Evolutionary
Innovation
Kelly and Pyenson,
Science 2015

14. Parallel Evolution

16. Brief history of evolutionary theories
Populations
grow fast but
the resources
are limited

17. 2009: Darwin’s birth bicentenary year

19. The theory of Natural selection

21. Limitations of Darwinism
• When Darwin proposed his theory of Natural selection, neither the
laws of inheritance nor mutations were known.
• Darwin could not explain why along time variability should not
disappear and evolution should not stop

22. Levels of Evolution

23. Evolution at the population level:
Population Genetics

25. Mutation: The main source of variation
Synonymous Non-Synonymous

26. Mutations and alleles

27. Natural Selection
• Differing viability and/or fertility of different
genotypes
• Accounts for ‘Adaptive’ Evolution
• Certain traits in a population are under selection
• Individuals with ‘adaptive’ trait more successful
than others in passing on their genes (Higher
Fitness)
• Offspring inherit that ‘adaptive’ trait
• Under strong selection pressure adaptive traits
become universal => Populations evolve

28. Population is a factor!
• For selection to operate, we need a large, diverse population, where the
individuals differ in respect to certain trait
• In the absence of individual variation, selection does not occur
(Neutrality)
• In a small population, the change in allele frequencies mostly take place
by chance alone (Genetic Drift)

29. • Sexual Selection
• Group Selection
• Kin Selection
• Ecological Selection
• Artificial Selection
Natural Selection is NOT the only Selection

30. Selection is NOT the only factor the causes evolution:
• Accounts for Non-adaptive Evolution
• Change in allele frequency in a population due
to chance event/sampling error
Genetic Drift

31. Hardy-Weinberg Equilibrium: the null model of
evolution
• HWE = NO evolution

32. From population to species: the next level

33. Species concepts
• Group of interbreeding natural populations
reproductively isolated from each other (Mayr
1942): Biological species concept
• The smallest discernable cluster distinguished by
a unique set of traits (Cracraft, 1982):
Phylogenetic species concept
• A lineage that has its own evolutionary tendencies
and historical fate independent of other lineages
(Simpson 1961): Evolutionary species concept
• Distinct non overlapping ecological niche (Van
Valen 1971): Ecological species concept

34. Speciation

35. The next level is - Phylogenetics

37. Application of Evolutionary Biology in the
Genomic era

38. Natural selection and Aging

39. Natural selection and cancer

40. Phylomedicine: Darwin for disease
“Phylomedicine is emerging as an
important discipline at the intersection of
Molecular Evolution and Genomic
Medicine. It focuses on the
understanding of human disease and
health through the application of long-
term molecular evolutionary history. It
was great to have pioneers in the field
of genomic and evolutionary medicine
at ASU to present and discuss their
recent research findings.”
Prof. Sudhir Kumar, Arizona State University, USA

41. Application of genomics in conservation

42. Artificial selection

43. Tracing our ancestry: Who am I?

45. Re-think