1. BY
PRASHANT VELLORE
BSc.BIOTECHNOLOGY
2011BSB817/11RSS75088

2.  Ever since people began to wonder at the world around
them they began to ask questions like….
i. How a horse always gives birth to a horse?
ii. Why does a baby always resemble it‟s parents or it‟s
grandparents?
 The first theories came down through the thoughts of the
early Greek philosophers also called the natural
philosophers.
 But before they explained these questions in rational terms
they were already answered by myths, old enough.

3. •About six thousand years ago people started keeping
record of pedigrees of domestic animals such as horses
and food plants like rice.
•The ideas or theories which have been forwarded from
time to time to explain the phenomenon of inheritance
can be categorized as….
THEORIES
VAPOUR AND PREFORMATION PARTICULATE
FLUID THEORIES THEORIES THEORIES

4.  PYTHAGORAS(500BC)
proposed that every organ
of animal body gives out
some type of vapours .
These vapours unite and
form a new individual.

5.  HIPPOCRATES(400BC)
believed that the
reproductive material is
handed over from all parts
of the body of an
individual , so that the
characters are directly
handed over to the
progeny.

6.  ARISTOTLE (350BC)
thought that the semen
has some “vitalizing”
effect and considered it as
the highly purified blood.
According to him the
mother furnishes inert
matter and the father gives
motion to the new life.

7.  LEONARDO DA VINCI
(1452-1519)
proposed a theory that the
male and the female
parents contribute equally
to the heredity of the
offspring.

8.  WILLIAM HARVEY(1578-
1657)
speculated that all animals
arise from eggs and semen
plays only the vitalizing
role.

9.  A.V. LEEUWENHOEK (1632-
1723)
in 1677 he observed
sperms of different
animals like man, dog, and
other mammals like frog,
fish, etc. and named it as
„animalcules‟ and also
suggested their association
with eggs.

10.  HOMUNCULUS
some scientists speculated
that they saw a „little man‟
or Homunculus in the
sperms.

11. PREFORMATIONISTS HAVE OFTEN
BEEN DIVIDED INTO TWO SCHOOLS
SPERMISTS/
OVISTS
ANIMALCULISTS

12.  OVISTS  SPERMISTS/ANIMALCULISTS
these group of scientists these group of scientists
attached more importance to attached more importance to
ova or egg, they thought that sperm, they thought that
„homunculus‟ was present in „homunculus‟ or a complete
the ovum, and thus it was the organism was present in the
women who carried the eggs sperm, and contended the
containing boy and girl only contribution of female
children and was responsible was the womb where the
for the gender of the „homunculus‟ grew.
offspring.

13.  There was a theory which disapproved this theory.
 It was given by K.F.Wolff and was called
„THEORY OF EPIGENESIS‟.

14.  K.F.WOLFF(1738-1794)
finally refuted the
preformation theory by
proposing that neither eggs
nor sperm had the structure
like „humunculus‟ but
gametes contained
substances capable of
forming the organized body
after fertilization. This idea
was the very core of THE
THEORY OF
EPIGENESIS.

15.  This theory suggested that many new organs and tissues
which were originally absent, develop subsequently.
 However ,Wolff believed that these tissues and organs
developed due to some mysterious vital forces.

16.  French biologist MAUPERTUIS (1689-1759) proposed that
the body of each parent gives rise to minute particles.
 During sexual reproduction the particles of both individuals
unite together to form a new individual.
 He thought that in certain cases the particles of the male parent
might dominate on those of the female parent and produce the
male individual,while in the production the particles of female
might be dominant on particles of the male.
 Thus he proposed the concept of biparental inherentance by
elementary particles.

17.  PARTICULATE THEORIES were given in different forms
like
1) Inherentance of acquired characters,
2)Theory of Pangenesis,
3)Theory of Germplasm.

18.  LAMARCK (1744-1829)
in 1844 proposed the
phenomenon of
“inherentance of
acquired characters”
among living organisms.
But he failed to provide
convincing evidences in
support of his concepts.

19.  HIPPOCRATES
gave the central idea of the
pangenesis theory.

20. CHARLES DARWIN
In 1868 gave his famous theory
of pangenesis which exclusively
depends on the particulate
theory.
According to it each part of the
animal body produces many
minute particles known as
gemmules ,which are first
collected in the blood and then
concentrated in the reproductive
organs.
When the animal reproduces
into new individual ,these
gemmules pass on to it and it has
blending of both parents.

21.  WEISMANN (1835-1934) and GALTON (1823-1911)
disapproved the Theory of Pangenesis.
 WEISMANN in 1892 postulated
“Theory of Germplasm” to explain heredity.

22.  WEISMANN (1835-1934)
according to this theory
explained that the body of
the organisms contain two
types of cells namely
„somatic cells‟ &
„reproductive cells‟. The
somatic cells make up the
body and it‟s various
organs, while the
reproductive cells form the
sperm and ova.

23.  The somatic cells contain the „somatoplasm‟ and germinal
or reproductive cells contain the „germplasm‟.
 According to Weismann the germplasm can form the
somatoplasm but vice-versa does not take place.
 The changes in the somatic cells due to environment
cannot influence the reproductive cells.
 Even after cutting the tail of mice for many generations he
always got tailed mice.
 Thus, by such experiments he rejected Lamarckism and
Pangenesis Theory.

24.  Though The particulate Theory faced many problems
in it’s beginning but its basic concept has formed the
central core of the modern understanding of Genetics.