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MICRO
MACRO & MEGA
EVOLUTION
Dr. JAGDISH KAUR
P.G.G.C.,Sector 11, Chandigarh
EVOLUTION
 Evolution is change in heritable traits of biological
populations over successive generations.
 Evolutionary proceses give rise to diversity at every
level of biological organisation, including the levels of
species, individual organisms and molecules.
 All life on earth shares a common ancestor known as
last universal ancestor which lived approximately 3.53.8 billion years ago.
 A study in 2015 founds “remains of biotic life” from 4.1
billion years ago in ancient rock in Western Australia.
THE HISTORY OF LIFE
 Biological evolution consists small scale evolution and
large scale evolution.
 The central idea of biological evolution is that all life
on earth shares a common ancestor.
 Through the process of descent with modification, the
common ancestor of life on earth gave rise to the
fantastic diversity.
 Evolution means we’re all distant cousins ; humans and
oak trees , humming birds and whales.
THE HISTORY OF LIFE
CHANGE THROUGH
SHORT TERM CHANGE TIME
SHARING COMMON
ANCESTOR
HUMAN EVOLUTION
CHANGE THROUGH TIME
BASIC PATTERN’S OF EVOLUTION
 The basic pattern can be described as;
 Movement of evolutionary line with subdivisions of
subzones as Microevolution.
 Movement from one zone or subzone to other as
Macroevolution.
 Movement from one major set of zones into other
into others as Megaevolution.
BASIC PATTERN’S OF EVOLUTION
 Evolutionary phenomenon can also be dealt with at three
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levels in another way as proposed by Goldschmidt:
Evolutionary changes occur within a population –
Microevolution.
Evolution of all major groups beyond species as
Macroevolution.
Some author however like Simpson divided evolution of
major groups further into two subtypes;
[a] Macroevolution – evolution of genera,families& order.
[b] Megaevolution – evolution of class and phyla.
MICROEVOLUTION
 Evolution resulting from the interaction of variation,
mutations, natural selection and genetic drift to
produce relatively small population changes.
 ‘Micromutations’ or ‘little mutations’ as described by
Goldschmidt, is considered to be the ultimate source
of new alleles or gene combinations, in addition to
recombination which also changes the gene frequency
in the gene pool of the population.
 A third elemental force responsible for fixing in
populations of non-adaptive or neutral characteristics
is genetic drift, which plays an important role in
evolution, particularly in small populations.
MICROEVOLUTION
 However, the impact of the total environment on the
reproduction and selection of gene combinations is
through the force of natural selection.
 It doesn’t directly produce new genes or gene
combinations, but helps to mould or differentially select
genetic variations present in a population.
 Thus, the whole process of microevolution can be
conjectured as follows;
 The elemental forces of evolution i.e.. Mutation ,
recombination and migration produce variations in genetic
material. They initiate microevolutionary process whereas
natural selection and genetic drift once sort out these
variations helps to establish the process.
MUTATION
 Some green genes beetles randomly mutated to brown
genes [although since any particular mutation is rare,
this process alone can not account for a big change in
allele frequency over one generation].
MIGRATION
 Some beetles with brown genes immigrated from
another population or some beetles carrying green
genes emigrated.
GENETIC DRIFT
 When the beetles reproduced , just by random luck
more brown genes than green genes ended up in the
offspring.
 Brown genes occur slightly more frequently in the
offspring [29%] than in the parent generation[25%].
NATURAL SELECTION
 Beetles with brown genes escaped predation and
survived to reproduce more frequently than beetles
with green genes, so that more brown genes got into
the next generation.
SPECIATION
 The origin of new populations can occur in two basic
ways:
 In a Successional Manner (Species Transformation)
It results in successional replacement of pre-existing
population by the new ones e.g. Palaoentological
series.
 In a Divergent Manner (Species Divergence)
 It results in the splitting of parental population into
two or more new populations with the appearance of
genetic divergence.
 Isolation is the additional factor, which establishes
genetic divergence
MACROEVOLUTION
 It is an evolutionary pattern, which results in the
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production of new adaptive types through a process of
population fragmentation and genetic divergence.
This type of evolution involves:
(i) an early formative phase; and
(ii)a subsequent period of expansion and
proliferation
and is characterised by:
(a) Subdivision of group into several new subgroups.
(b) Invasion of several new environmental situations.
(c) Diversification of structure and biology.
MACROEVOLUTION
 The term macroevolution was given by Iurii
Filipchenko a Russian geneticist and developmental
biologist in 1927.
 The concept of macroevolution or adaptive radiation
as such was given by Osborn in 1910 in relation to
mammalian evolution.
 He wrote in “Age of Mammals” that adaptive radiation
might be defined as that phenomenon where
representatives of large systemic groups adapt
themselves to a number of mutually exclusive ways of
life.
EVOLUTION OF HORSE
 Evolution of horse represent the best-documented
example of macroevolution in the fossil records.
 Evolution of Horse family Equine from Hyrecotherium
to Equus exhibited gradual changes in the structure of
teeth, limbs, hoof, size etc.. .
 From a small fox-like browsing creature with padded
feet to modern horse with large size, grazing habits
and hoofed feet.
ADAPTIVE RADIATION
 It is a process in which organism diversify rapidly into a
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multitude of new forms, particularly when a change in
the environment makes new resources available,
creates new challanges.
It starts with a single recent ancestor , this process
results into speciation.
Also species exhibits different morphological and
physiological traits.
Due to availability of abundant resources and diverse
habitats, thereis a population increase, which leads to
high selection pressure.
Therefore, the newly entered populations enter all the
available habitats of the new adaptive zone.
ADAPTIVE RADIATION
MARSUPIALS OF AUSTRALIA
ADAPTIVE RADIATION IN DOGS
DARWIN’S FINCHES
 Darwin’s finches are a group of about fifteen species of
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passerine birds.
They are often classified as the subfamily Geospizinae
or the tribe Geospizini.
They belong to tanager family and are not closely
related to the true finches.
First collected by Charles Darwin on the Galapagos
island during the second voyage of the Beagle.
Term “Darwin’s finches” was first applied by Percy
Lowe in 1936 and popularised in 1947 by David Lack in
his book Darwin’s Finches.
DESCRIPTION
 The birds vary in size from 10-20 cm and weight
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between 8-38 grams .
The smallest are the Warbler finches and the largest is
the Vegetarian finch.
The most important differences between species are in
the size and shape of their beaks.
The birds are highly adapted to different food sources.
Due to adaptation of different diet, results in variation
The birds are dull coloured.
TYPES OF MACROEVOLUTION
 There are two types of macroevolution; Divergent and
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convergent.
Divergent evolution
When two different species share a common ancestor, but
have different characteristics from one another.
Exmple; Darwin finches.
Convergent evolution
When two different species do not share a common
ancesstor, but have developed similar characteristics
through adaptation to similar environmental conditions.
Example; Hummingbird and a hummingbird moth.
MEGAEVOLUTION
 Megaevoution describes the most dramatic events in the
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evolution.
Megaevolution is used for great changes.
Megaevolution has been extensively debated because it has
been seen as a possible objection to Charles Darwin theory
of gradual evolution by natural selection.
The Cambrian explosion or Cambrian radiation was the
relatively rapid appearance of major most animal phyla
around 530 million years ago in the fossil record, some of
which are now extinct.
It is the classic example of megaevolution.
CAMBRIAN EXPLOSION
 Before about 580 million years ago it seems that most
organisms were simple. They were made of individual
cells occasionally organised into colonies.
 Over the following 70 or 80 millions years the rate of
evolution accelerated by an order of magnitude.
 Normally rates of evolution are measured by the
extinction and origination rate of species but here we
can say that by the end of Cambrian every phylum or
almost every phylum, existed.
 The diversity of life began to resemble with that of
today.
•Cambrian fossil Opabina
•Thought to be unrelated to any phylum.
•Closely related to the ancestors of arthropods.
The Cambrian organism Marrella
Clearly an artropod