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Lamarckism development, while disuse for a long time make them

undeveloped and ultimately lead to their degeneration.
Lamarckism is also known as the theory of inheri- { 4) Competition— There is a sort of competition in
tance of acquired characters. Lamarckism is the first
theory of evolution, and was proposed by Jean Baptiste
nature to avoid overcrowding on earth. The stronger orga -
nisms try to destroy the weaker ones. The smaller multiply
de Lamarck ( 1744-1829 ), a French biologist. Although the
faster , while larger ones slowly, thus a balance is main-
outline of the theory was brought to notice in 1801, but his
tained.
famous book ' Philosophic Zooiogique was published in 1

(5) Inheritance of acquired characters— The favou-

1809, in which he discussed his theory in detail. Lamarck
rably structural changes gained by an individual due to
coined the terms 'invertebrates ' and ' Annelida . The 1

term ' Biology ' was given by Lamarck and Treviranus.

use or disuse during its life time is preserved and are
passed on to its offsprings. These changes become more
Lamarck also introduced the term ' Vertebrates'.
and more pronounced if they are exposed to similar stress
Lamarckian Postulates or Laws : of the environment as was faced by their ancestors or
parents . Such cumulative effects will finally result in the
The complete theory of evolution given by Lamarck
appearance of new species.
(Lamarckism) is popularly known as the inheritance of
acquired characters in organisms . It is in the form of four Cross breeding— These various peculiarities pro-
postulates or laws, as follows : duced in the organisms will always appear in successive
generations (provided breeding is confined to such unions
1. The internal forces of life tend to increase the size of
an organism, he. the whole body and also the diffe -
only ) . As a result , crosses between individuals not acqui -
ring these peculiarities, result in the disappearance of
rent parts upto a limit determined by life itself.
such characters acquired in particular circumstances.
2. The formation of a new organ or a part in the body is
Isolation— The separation of various generations
the result of a new need or new want, which has
brings about their different features, which in the course of
arisen and continues to be left by the organism.
evolution, become specialized into particular species .
3. The development of an organ and its power of action
is directly proportional to its use, continuous and Analysis of Lamarck’ s Theory :
constant use strengthening the organ, while disuse
First law — The first law of Lamarck is merely the
results in its degeneration.
growth process of the organism with which most scientists
4. All the changes, which organisms acquire during their agree. The increase in size in living beings is common
life time are transmitted to their offsprings by the due to metabolic activities, which are controlled by vital
process of inheritance, It means changes are cumula - forces of life.
tive over a period of time. Second law— This law of development of an organ
The fourth principle that is acquired characters are due to its need is unacceptable to the modern evolu -
inherited, is the most attractive and controversial law, now tionists. Nobody can believe that any organ can develop
known as ’Lamarckian doctrine'. due to the need of its presence.
A more precise account of Lamarck ’s theory may be
given by the following factors, which according to him ,
—
Third law The principle of use and disuse of organs
were based on direct observation of nature. Some of the
played an essential role in evolution : examples are as follows—
( 1) Role of environmental factors— Lamarck be- (1) Ancestors of modern horse lived in soft ground in
lieved that various factors like soil, food, temperature etc. forests and were plantigrade. These forests were later
Causing changes in environment act directly in case of replaced by dry grass plains, and these had to graze on
plants, while indirectly in case of animals ( since they hard grass and to walk on dry land. These changes in
possess nervous system). The environment influence habit were followed by changes in premolars and molars,
leads to change in their habits which results in unusual reduction in number of digits and lengthening of legs.
activity of an organ or structure. Lamarck, thus assumed Thus the foot was gradually changed to unguligrade .
that living organisms react to external conditions and suited for swift running over hard ground.
become modified. ( 2) The continuous stretching of neck for several
( 2) Effects of needs or physical wants— Lamarck generations by giraffe to catch high located leaves and
thought that change of habits may bring about the modi - fruits of tall trees, caused the lengthening of its neck . This
fication of existing organs or may initiate the formation of was due to continuous use of particular organ (neck) that
new organ. enabled them to eat the food.
—
( 3) Use and disuse The continuous and constant
use of organs make them efficient and lead to their better
( 3) The muscles on the upper part of the body of a
blacksmith are well developed due to constant use.
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 ( 4) The whales lost their hindlimbs as the conse - and every generation. This dearly proved that acquired
quences of the inherited effect of disuse. characters are not inherited.
(5) Snakes have elongated body accompanied by (5) Experiment by Castle and Phillips— Recently
loss of limbs. The continuous creeping through holes and Castle and Phillips performed transplantation experiments
crevices made limbs. continuously useless, hence finally to show the environment has no effect on heredity. They
degenerated. took a black female guinea pig * its ovary was removed
Besides these, there are other examples, like vesti - and transplanted into the body of white female guinea pig.
gial organs in living animals due to disuse; claws in The white female (with the ovary from black female) was
carnivores, sensitive skin and tactile points on the ventral mated with a white male guinea pig. He found that all the
side of the body; callosities of palm in hard workers; offsprings of this pair were black. This dearly showed that
webbed feet in swimming birds , etc., exemplifying environment has no effect on heredity. Hence, this again
Lamarckian theory. disapproves Lamarckism. However some later workers
The transmission of acquired characters is the impor- have found that in certain cases environment has some
tant principle usually termed as the ’Lamarckian doctrine*. effect on heredity.
The acquired characters use hereditary or not, /.e., Likewise, there are numerous cases non-hereditary
whether any structural change induced, in the body by nature of acquired characters. Hence, it is obvious that
use or disuse or by a change in surrounding environment variations due to mutilations and diseases are not inhe-
can affect the germplasm in such a way that offspring will rited; otherwise, non of us would have existed without
acquire these structural modifications or not, is debatable. some trace of hereditary crippling.
Significance of Lamarckism : Neo-Lamarckism :
Lamarckian theory was simple and it had some The evolutionist who support the Lamarckian doctrine
appeal, as it provided a way in which changes in orga - of inheritance of acquired characters come under the
nisms cculd come about. It was the first completely com- heading of Neo-Lamarckism. Among the notable suppor-
.
prehensive mechanistic theory that was offered Further- ters of New-Lamarckism are Cope, Giard, Packard, Spen-
more , it was the theory that lent itself to predictions ahd, cer and McBride. They tried to modify Lamarckism in
therefore, to testing. Thus, Lamarckian theory enjoyed
popular acceptance for near about 70 years, because it
-
order to make it acceptable. These Neo Lamarcklans con
sidered that adaptation is universal. It arises as a result of
-
was exemplified by many common examples. Most per- casual relationship of structure, function and environment.
sons know that exercise results in larger muscles. Changed environmental conditions alter habits of orga -
nisms, hence, in response to new habits, organisms
Criticism of Lamarckism :
acquire new structures in place of old structures. Conse-
The Lamarckian doctrine has been criticised much, quently, variations among animals have become distinct.
Cuvier and Weisman were the great critics of Lamarckism. These variations have finally become engrained in the
The following are the main objections against the inheri- heredity of the race. The kind of argument is, in fact, a
tance of acquired characters— modified version of Lamarckian principles , because it has
(1) Experiment by Weismann— August Weismann, omitted Lamarck’s view that of general perfecting ten-
a German biologist was the main opposer of the inheri- dency in evolution.
tance of acquired characters. He put forward the theory Thus modem modified form of Lamarckism is known
of continuity of germplasm. According to Weismann, as Neo-Lamarckism. Weismann s theory is also not very
1

the characters influencing the germ cells are only inheri- satisfactory. In some cases the characters are also trans-
ted. There is a continuity germplasm (Protoplasm of germ mitted through somatic cells, ag., regeneration in some
cells) but the somatoplasm (protoplasm of somatic cells) animals like earthworms and vegetative propagation in
is not transmitted to the next generation, hence it does not plants. It means that somatic ceils also contain all the
carry characters to next generation. Weismann cut off tails characters. Environment can influence the form, size
of rats for about 80 generations and allowed the mutilated colour etc., of the organism, which may be inherited to the
parents to breed, but tailless rats were never born. Jt next generation. Tower exposed the young ones of potato
means that acquired character was not inherited. beetles to abnormal conditions of temperature and mois -
( 2) Experiment by Loeb— Loeb produced artificial ture and allowed them to breed, He observed marked
parthenogenesis In the sea urchin’s egg with the help of changes in the next generation of beetles. Morgan
chemical stimuli. Similar eggs, were produced in corres - exposed normal fruit flies (Drosophila) to X -rays in a
ponding environments in brine shrimp Artemia salina but particular surrounding and found some remarkable
none of their generation showed acquired characters. changes in the offspring, which were also transmitted to
—
(3) Indian traditions Boring of ears and nostrils in
Indians has been continued from centuries among human
the next generation. Agar reared water fleas in a culture
of green flagellates and found that some abnormalities
beings, but their offsprings do not show any trace of holes were developed in their structures. The parthenogentic
in ears and nostrils. eggs of such individuals when kept in ordinary water and
( 4 ) Experiment by Pavlov — Pavlov was a Russian allowed to hatch, produced individuals with the same
scientist , who wanted to show the inheritance of learning. abnormalities. Guyer and Smith broke the lens of eye a
He trained the mice to come for food on hearing a bell. male rabbit by means of a needle. The surrounding blood
But it was found that this training was necessary for each capillaries penetrated the damaged area. The made rabbit

C.S.V./ February / 2001 / 1658

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was allowed to mate a normal female who gave birth to Darwinism
seven young ones, four of which had defective eyes. It is
clear that the antibodies induce mutation in genes con - Darwin's Theory of Natural Selection :
.
trolling eye development It indicates that the acquired Charles Darwin was an English naturalist. In 1331,
characters can be inherited, .if the body changes produce Darwin got an opportunity to travel on H.M.S . Beagle (a
antibodies which in turn induce changes in the genes ship in which Charles Darwin sailed around the world) for
concerned with the character. a voyage of world exploration. The voyage lasted for five
-
The radio active rays, certain chemicals and hor - years. During that period Darwin explored the fauna and
mones can influence the chromosomes and genes of the .
flora of a number of continents and islands Later Beagle
germ cells and can bring about the changes in the next was sailed to the Galapagos Islands, where Darwin
generation. It is also believed that somatic changes may observed great variations among the organisms that lived
be affecting the germ cells through some means. on these islands. The common birds of Galapagos
-
Thus New Lamarckism proposes that — Islands, the finches were markedly different from the
finches of mainland. In fact Darwin took idea from the
1. Environment influences the organism and
change its heredity. finches found on the Galapagos Islands for his theory of
natural selection.
2. Some of the variations acquired by an individual
can be transmitted to the next generation. Alfred Russel Wallace, another English naturalist,
3. Internal vital force and appentency do not play
who travelled widely, and studied the fauna and flora of
any role in evolution. South America and South East Asia. Evolutionary ideas
similar to those of Darwin developed in Wallace’s mind.
4. Only those variations are transferred to the next He expressed these ideas in an essay titled ‘ On the
generation which also affect germ celts or whfere Tendency of Varieties of Depart Indefinitely from the
somatic cells give rise to germ ceils. Original Type'. Wallace sent his essay to Darwin. By the
Conclusion : time Darwin received Wallace’s essay , he had developed
a clear idea about organic evolution. The thinking of both
The above objections and evidences on the' inheri- Darwin and Wallace in respect of organic evolution was
tance of acquired characters are unconvincing and un- similar. Finally in 1859, Darwin published his observations
satisfactory. The main theories in this regard are 'Mrieme and conclusions under the name 'Origin of Species’.
theory of Semon’ and ‘ -
Centro epigenesis theory of Darwin' s this publication became very popular and
Rignano’. Semon holds that every condition of life or changed people's thinking about organic evolution.
functional activity of organism leaves a permanent record
1
.
of itself in the form of 'engramme If these conditions are The Main Features of the Theory of Natural
continued for long period, these engrammes affect here - Selection are as Follows :
dity and become inheritable; but if they are of short
duration, they do not inherit. It is clearly established that (1) Overproduction (Prodigality or Fecundity ) — All
only those characters, which can affect germplasm organisms possess enormous fertility. The productivity of
(germinal or blastogenic) can be inherited, while other all living organisms is far beyond the ultimate numbers ,
characters (somatic or somatogenic) affecting body ceils which can possibly survive. The space and the available
do not transmit to their offsprings. food supply remain the same, while their quantity in -
creases enormously , /.e., in geometric ratio. It is the
Differences between Lamarckism and Neo- innate desire of all living beings to produce their own pro -
Lamarckism geny for the continuity of race.

Neo-Lamarckism For example; insects lay hundreds of eggs. Plants

Lamarckism
produce thousands of seeds. A female rabbit gives birth to
1. It is the original theory given 1. It is a modification of the six young one in one time. If all the rabbits survived and
by Lamarck. original theory of Lamarck
multiply at this rate, their number would be very large after
in order to make it more
suitable to modern know- sometime, it is assumed that elephant is the slowest
ledge. breeder , which matures at the age of 30 years and lives
2. The theory lays stress on 2. Neo -Lamarckism does not
for about 90 years. Each female gives rise to about six
internal vital force, appe- give any importance to offsprings and if all survived, in 750 years a single pair
tency and use and disuse these factors. would produce about 19 million elephants. Thus some
of organs. organisms produce more offsprings and others produce
3. It believes that change In 3. The theory stresses on the fewer offsprings. This is called differential reproduction.
environment brings about a direct effect of changed en- All this indicates that every species of animals and
conscious reaction in ani- vironment on the orga- plants has an extraordinary power of production , and for
mals. nisms.
controlling this over productivity , these should be some
4. According to Lamarckism 4 , Normally only those modi- efficient check . Darwin and Wallace both recognized the
the acquired characters are fications are transferred to
natural check and called it the struggle for existence.
passed on to the next the next generation which
generation. influence germ cells or (2) Struggle for existence— As a result of geome-
where somatic cells give trical multiplication of individuals, the food and space
rise to germ ceils. remain almost constant, with the result that a struggle
C.S.V. / February / 2001 / 1659

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t
inevitably follows for existence. This struggle for existence ted the survival of the fittest by natural selection by taking
may be between the individuals of the same species example of Lamarck's giraffe. Giraffe showed great varia-
(intraspecific struggle) or between different species (inter - tions in the length of their neckand legs. Due to scarcity
specific struggle) or due to environmental factors (struggle of grass on the land, these had to eat the leaves of tall
with the environment of inanimate nature). Consequently trees. Naturally giraffe with long neck and longer legs had
it is of three types— an advantage over those with shorter necks and legs,
(i) Intraspecific struggt It is the struggle bet- since these could get enough food easily, had better
ween the individuals of the same species or in chances of survival and others having shorter necks and
closely related forms to gain upper hand. It is the legs gradually became extinct. Due to variations and
most severe check, because their requirements inheritance, the successive generations gradually became
like food, shelter, breeding places are similar . better adapted to their environment. These adaptations
are preserved and accumulated in the organisms of a
Many human wars are the examples of intra-
specific struggle. Cannibalism (eating the indivi - species and ultimately lead to the origin of new species.
The environment is ever changing due to which further
duals of its own species) is another example of
this type of struggle. changes occur and new adaptations appear in the
organisms. The descendants after several generations
—
(ii) Interspecific struggle This struggle is more become quite distinct from their ancestors. In this way
frequent occurring between the individuals of new species appear.
different species living together, individuals of the
species compete with individuals of other spe- Some of the variations exhibited by living things make
cies, normally for food and shelter. it easier for them to survive, others are handicaps which
bring about the elimination of their possessors. The idea
(iii) Environmental struggle— It is the struggle bet - of 'the survival ol the fittest' is the core of the theory of
ween the organisms and the environmental fac- natural selection. *
tors, such as drought, heavy rains, extreme heat
or cold, earthquake, disease etc. Thus climate Evidences in Favour of Natural Selection :
and other natural factors also help in restricting
the number of individuals of particular species. —
(1) Rate of reproduction Rate of reproduction is
many times higher than the rate of survival in all
(3) Variations— The fact that no two organisms or
organisms,
parts of the organisms are exactly alike, no matter how
closely related, is a commonly observed phenomenon. (2) Limitation of resources— Food, space and other
These differences are called variations. It is the basic resources are limited.
prerequisite and progressive factor for evolution, because 11
4 . I

without variations, no change could occur and evolution (3) Struggle for existence— Competition or struggle
would be impossible. But all the variations are not signi- for existence is seen in all organisms,
ficant from evolutionary point of view. Some of them are
changes occurred temporarily in the soma of the orga - —
( 4) Abundance of variations Variations are so
abundant in nature that no two individuals of a species are
nisms and are not inherited to the offsprings. Only those
similar , not even the monozygotic twins.
variations which can be inherited can take part in the
evolution of species. These variations are called heritable (5) Production of new varieties of plants and
variations. Changes occurred in the genes, or the chromo - —
animals by sexual selection When man can produce
somes of the germplasm are the only heritable variations. various new varieties of plants and animals in a short
period, nature with its vast resources and long time at its
Darwin observed the various useful variations which
disposal oan easily produce new species by selection.
are selected by individuals and thus evolution results.
Darwin assumed variations as axiomatic without describ- (6) Mimicry and protective colouration — They are
ing their real nature and origin in plants and animals. Thus found in certain animals and are products of natural selec -
according to Darwin, the variations are continuous and tion.
those which are helpful in the adaptations of an organism
(7) Pedigrees of some animals — Pedigrees of
towards its surroundings would be passed on to the next
horses, camels and elephants also support the Natural
generation, while the others disappear.
T"' i Selection Theory.
(4) Survival of the fittest and natural selection—
The organisms which are provided with favourable varia - Objections to the Theory of Natural Selection
tions would survive, because they are the fittest to face (Darwinism) :
their surroundings, while others are destroyed. Originally it
was an idea of Herbert Spencer, who used the phrase the
Some of the objections to the theory of natural selec -
survival of the fittest ’ first time. While Darwin named it as
tion, which Darwin explained vaguely are the following —
'Natural Selection’. The survival of the fittest is the result (1) If species have descended as a result of grada -
of natural selection, which enforces adaptations. In the tions, there should be innumerable transitional stages and
course of long periods those best fitted and suitable the species should not be so well defined as they are.
individuals survive and become adjusted to nature. Nature Darwin’s theory stresses upon small fluctuating variations
being the super power selects only those adapted orga- which are to a large extent noninheritable and can play no
nism which have accumulated variations. Darwin illustra- part in evolution.
C.S.V./ February / 2001/ 1660

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t
 (2) His theory does not explain the effect of use and
disuse and the presence of vestigial organs.
—
( 1 ) Mutations Alteration in the chemistry of gene
(DNA molecule) is able to change its effect is called gene
(3) He could not explain whether the instincts are mutation. They are discontinuous variations which develop
acquired and modified through natural selection or not. due to permanent changes in genotype. Mutation can pro-
duce drastic changes or can remain insignificant. There
( 4) He did not differentiate between somatic and
are equal chances of a gene to mutate back to normal.
germinal variations and considered all variations as heri
table.
- Most of the mutations are harmful or deleterious but not
all. Most of the mutants are recessive to normal gene and
( 5) Natural selection cannot account for degeneracy. these are able to express only in homozygous state. Thus
(6) One of the classical objections to natural selection mutations produce variations in the offsprings.
is that new variations would be lost by 'dilution' as the (2) Variations and heredity— The nature of genetic
individuals possessing them breed with others without variations caused by reshuffling of genes during sexual
them. reproduction was very tittle known at the time of Darwin.
Darwin indirectly accepted the Lamarckian idea of The phenomenon of meiosis causes random assortment
pange-
inheritance of acquired characters in the form of ‘ of genes during synapsis and rearrangement of maternal
nesis hypothesis’, which cannot be accepted in the light of and paternal chromosomes in both kinds of gametes.
knowledge of genetics. Such a reassortment of genes in a large population with
large gene pool is the basis of appearance of new orga-
Darwin's Pangenesis Theory : nisms.
To expiain the inheritance of characters from parents -
Crossing over of genes during meiosis also adds to
to the offspring, Darwin proposed the theory of pange
nesis. It is now totally discarded. The following are the
- the variations and chromosomal aberrations like inversion,
translocation and polyploidy also result in the origin of
main points of pangenesis hypothesis : new species.
(1) All the somatic cells of the body not only multiply Heredity is the transmission of characteristics or
by cell division but also give off minute particles through- variations from parent to offsprings, is an important
out their life called as pangenes or gemmules, which .
mechanism of evolution Organisms possessing here -
wander throughout the body. ditary characteristics that are helpful, either in the animal' s
(2) There gemmules later on become concentrated in native environment or in some other environment that is
the germ cells in both the sexes. open to it, are favoured in the struggle for existence. Con-
sequently, the offsprings are able to benefit from the
(3) Each germ cell is a minute replica of the parent ’s
advantageous characteristics of their parents.
body and is capable of developing into the same kind of
body even in minute details. (3) Genetic drift— It is the elimination of the genes of
certain characters when a section of population migrates
(4) Each gemmule in the developing individual regu-
or dies of natural calamity. It changes gene frequency of
lates the development of the organ from which it origina - remaining population .
ted from the parent.
(4) Natural selection— If differential reproduction
(5) These gemmules are continuously produced at all
( f.s., some individuals produce abundant offspring, some
stages of development.
only a few and still others none) continues for many
(6) Sometimes, certain gemmules might lie dormant generations, genes of the individuals which produce more
for several generations and then develop. It results in the offspring will become predominant in the gene pool of the
appearance of characteristics in the offsprings which were population. Thus natural selection occurs through differen-
born by their ancestors ( atavism) and are not visible in the tial reproduction in successive generations. Thus the
parents . population becomes diverged either from the parent
(7) The weakest link in Darwin’s theory of natural population or from sister populations.
selection was his ignorance of the mechanism of heredity. (5) Isolation— Isolation is a segregation or separation
Gallon— Made pangenesis hypothesis untenable by of populations by some barriers which prevent inter-
presenting several experimental proofs. According to breeding between related organisms. The reproductive
pangenesis theory, every somatic cell is a germ cell pro- isolation between the populations due to certain barriers
ducing gemmules, while the actual germ cells are the leads to the formation of new species.
collection place for the gemmules coming from different
somatic cells. Thus this theory has no basis at all and has
—
(6) Origin of new species The populations of a
species present in different environments and are segre -
been replaced by modern theory of germplasm put gated by geographical and physiological barriers, accu-
forward by Weismann. mulate different genetic differences due to mutations,
recombination, hybridization, genetic drift and natural
Neo-Darwinism : selection. The populations thus become different from
The modern theory of origin of species (evolution) is each other morphologically and genetically, and they
called modern synthetic theory of evolution. It is combi
nation of mutations, variations, heredity, isolation and
- become reproductiveiy segregated, forming new species.
Thus, new species arise by the establishment of some
natural selection. It is the modified form of Darwin’s reproductive barrier or isolation which checks the free
theory of natural selection. gene flow among populations of different environments.
.
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V
 Differences between Darwinism and Neo- The modem synthetic theory of evolution is the result
Darwinism of the work of a number of workers, namely R .A.
Darwinism Neo-Darwinism ..
Dobzhansky, RA Fisher, J B S. Haldane, Sewali Wright,
(Natural Selection) ..
Ernst Mayr and G L Stebbins. Mutations and natural
1. it is the original theory 1. Neo-Darwinism is a modifi - selection both are Important for organic evolution. Darwin
given by Charles Darwin cation of the original theory and DeVries in their theory of organic evolution did not
(1859) to explain the origin of Darwin to remove its consider the other factors which were essential beside
of new species. shortcomings.
natural selection and mutation for, organic evolution.
2 . According to this theory .
2 Instead of continuous
accumulation of continuous variations, mutations are
Stebbins in his book ‘Process of Organic Evolution’
variations causes change in believed to help form new
individuals to form new species. discussed the synthetic theory and other factors which
species. were responsible for evolution.
3. It believes in the selection .
3 Variations accumulate in the
of individuals on the basis gene pool and not in the
of accumulation of varia - individuals. Significant Facts of Evolution
tions.
4. Darwinism does not believe 4. Neo-Darwinism incorpora - .
Alpheus S Packard Jr. was the first to use the term
in isolation. tes isolation as an essential -
'Neo Lamarckism .
5

component of evolution.
G.J. Romanes coined the term ‘New-Darwinism'.
5. It can explain the origin of 5. The theory cannot explain
new characters. the origin of new charac - Polio's Rule state that evolution is irreversible. The
ters. generalization that evolution does not proceed back
6. Darwinism cannot explain 6. The theory can explain the along its own path, or repeat routes.
the persistence of certain occurrence of unchanged Cope’s Rule states that there is a tendency for animats
forms in the unchanged forms over millions of years.
to increase in size during the long course of evolution.
condition.
Bergmann’s Rule states that in geographically variable
Difference between Neo-Lamarckism and species of Homoiothermic animals , body size tends to
Neo-Darwinism larger in cooler regions of a species range.
Neo-Darwinism Neo-Lamarckism Allen’s Rule states that the extremities (tall, ears, feet ,
1. The theory explains that the 1. It is silent about high biotic bill) of endothermic animals tend to the relatively smaller
number of organisms of potential and geometrical in cooler regions of a species range .
different species remain the increase in population . Gause’s Rule or the Competitive Exclusion Rule
same despite their high bio - stales that two species having the same ecological
tic potential and ability to in- requirements cannot continue to occupy indefinitely the
crease by geometrical ratio.
same habitat.
2. It stresses the role of 2. The theory does not touch
struggle for existence and these aspects of evolu - Glogers Rule states that among warm blooded indivi -
natural selection in face of tionary forces. duals living in warm and wet climates, develop more
limited resources. melanin pigment, and are darker than those living in cold
3. It explains the role of varia- 3. The theory considers that climates.
tions, their origin and accu- the change in environment Jordan 's Rule states that fishes inhabiting water of low
mulation in the formation of produces modifications temperature tend to have more vertebrae.
new species. directly due to its effect on
The sum total of ail genes in a breeding population is
germ cells or rarely indi - called gene pool.
rectly through somatic cells.

OBJECTIVE QUESTIONS
1. The key point in Lamarck’s view 3. Galapagos islands are associa- (B) Sexual reproduction
of organic evolution is— ted with the name of — ( C ) Natural selection
(A) Origin of species (A) Wallace (B) Malthus
(D) Hormonal action
(C) Darwin (D) Lamarck
(B) Inheritance of acquired cha -
racters 4. Who published the book ‘Origin
6. Phenomenon of Industrial Mela
nism’ demonstrates—
-
of Species by Natural Selection
(C) Overpopulation (A ) Natural selection
in 1859 ?
(D) Natural selection (A) Lamarck (B) Oparin (B) Induced mutation

was—
-
2. Co discoverer of Darwinism (C) Wallace (D) Darwin (C) Geographical isolation
5. The ultimate source of organic (D) Reproductive isolation
(A) Ruskin (B) Buffon evolution is— 7. The unit of natural selection is
(C) Malthus (D) Wallace ( A) Mutation th
( Continued on Page ! 680 )
C.S.V./ February / 2001 / 1662

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