Centres of diversity – types of biodiversity – Centres of origin – Law of homologous series – centers of origin – types of centres of diversity – gene sanctuaries – genetic erosion – main reasons of genetic erosion – extinction – introgression – gene banks – types of gene banks

1. SUBMITTED BY : SHRUTI SAHU
ADMISSION NO : 33C/14
3rd YEAR, BSC(Ag)

2. WHAT IS CENTER OF ORIGIN OR
CENTER OF DIVERSITY?
A center of origin (or centre of
diversity) is a geographical area where a
group of organisms, either domesticated
or wild, first developed its distinctive
properties. Centers of origin are also
considered centers of diversity.

3. VAVILOV CENTER OF ORIGIN:
Vavilov centers are regions where a high diversity of crop
wild relatives can be found, representing the natural
relatives of domesticated crop plants. Later in 1935 Vavilov
divided the centers into 12, giving the following list:
1.Chinese center
2.Indian(Hindustan) center
3.Indo-Malayan center
4.Central Asiatic center
5.Persian center
6.Mediterranean center
7.Abyssinian center
8.South American center
9.Central American center
10.Chilean center
11.Brazilian center
12.North American center

4. (1) Mexico-
Guatemala, (2)
Peru-Ecuador-
Bolivia, (2A)
Southern Chile,
(2B) Southern
Brazil, (3)
Mediterranean,
(4) Middle East,
(5) Ethiopia, (6)
Central Asia, (7)
Indo-Burma, (7A)
Siam-Malaya-
Java, (8) China
and Korea

5. Types of Centres of Diversity of Crops
The centres of crop diversity of three types viz:
1) Primary centres of diversity,
2) Secondary centres of diversity
3) Micro –Centres.
These are briefly discussed below:
1. Primary Centres of Diversity:
Primary centres are regions of vast genetic diversity of
crop plants. These are original homes of the crop plants
which are generally uncultivated areas like, mountains ,
hills, river valleys, forests, etc. Main features of these
centres are given below:
1. They have wide genetic diversity.
2. Have large number of dominant genes.
3. Mostly have wild characters.
4. Exhibit less crossing over.
5. Natural selection operates.

6. 2. Secondary Centres of Diversity:
Vavilov suggested that values forms of crop
plants are found for away from their primary
area of origin, which he called secondary
centres of origin or diversity. These are generally
the cultivated areas and have following main
features.
1. Have lesser genetic diversity than primary
centres.
2. Have large number of recessive genes.
3. Mostly have desirable characters.
4. Exhibit more crossing over
5. Both natural and artificial selections operate.

7. 3. Microcenters:
In some case, small areas within the centres of
diversity exhibit tremendous genetic diversity of
some crop plants. These areas are referred to as
micro-centres. Microcenter is important sources
for collecting valuable plant forms and also for the
study of evolution of cultivated species. The main
features of micro centres are given below:
1. They represent small areas within the centres of
diversity.
2. Exhibit tremendous genetic diversity.
3. The rate of natural evolution is faster than
larger areas.
4. They are important sites for the study of crop
evolution.

8. Types of Biodiversity
1.SPECIES DIVERSITY
Every ecosystem contains a unique collection of
species, all interacting with each other. Some
ecosystems may have many more species than
another. In some ecosystems, one species has
grown so large that it dominates the natural
community. When comparing the biodiversity of
ecosystems, an ecosystem that has a large number
of species, but no species greatly outnumbering
the rest, would be considered to have the most
species diversity. A large number of species can
help an ecosystem recover from ecological
threats, even if some species go extinct.

10. 2.Genetic diversity
Genetic diversity is reliant on the heritable
variation within and between populations of
organisms. New genetic variation arises in
individuals by gene and chromosome mutations,
and in organisms with sexual reproduction it can
be spread through the population by
recombination. It has been estimated that in
humans and fruit flies alike, the number of
possible combinations of different forms of each
gene sequence exceeds the number of atoms in the
universe. Other kinds of genetic diversity can be
identified at all levels of organization, including
the amount of DNA per cell and chromosome
structure and number.

11. Selection acts on this pool of genetic variation
present within an interbreeding population.
Differential survival results in changes of the
frequency of genes within this pool, and this are
equivalent to population evolution. Genetic variation
enables both natural evolutionary change and
artificial selective breeding to occur. Only a small
fraction of the genetic material of higher organisms is
outwardly expressed in the form and function of the
organism; the purpose of the remaining DNA and the
significance of any variation within it are unclear.
Each of the estimated 109 different genes distributed
across the world’s biota does not make an identical
contribution to overall genetic diversity.

13. 3.Ecosystem or ecological diversity
Ecosystem diversity can be described for a specific
geographical region, or a political entity such as a
country, a state or a taluka. Distinctive ecosystems
include landscapes such as forest, grasslands,
deserts, mountains as well as ecosystems such as
rivers, lakes and the sea. Ecosystems are most
natural in wilderness areas. If natural ecosystems
are overused or misused, their productivity
eventually decreases and they are then said to be
degraded. Ecosystem diversity is often evaluated
through measures of the diversity of the component
species. This may involve assessment of the relative
abundance of different species as well as
consideration of the types of species.

14. Ecosystem diversity has three perspectives;
1.Alpha (α) Diversity
It is the biodiversity within a particular area, community
or ecosystem. It is usually expressed by the number of
species in that ecosystem. This can be measured by
counting the number of taxa within the ecosystem (e.g.
Families, genera and species).
2.Beta (β) Diversity
Beta diversity is a measure of biodiversity which works
by comparing the species diversity between ecosystems
or along environmental gradients. This involves
comparing the number of taxa that are unique to each
of the ecosystems. It is the rate of change in species
composition across habitats or among communities. It
gives a quantitative measure of diversity of communities
that experience changing environments.

15. 3.Gamma (γ) Diversity
It refers to the total species richness over a large
area. It is a measure of the overall diversity for the
different ecosystems within a region. It is a product
of alpha diversity of component ecosystems and the
beta diversity between component ecosystems.
Gamma diversity can be expressed in terms of the
species richness of component communities as
follows;
γ = s1 + s2 – c
s1 = the total number of species recorded in the first
community
s2 = the total number of species recorded in the
second community
c = the number of species common to both
communities

17. LAW OF HOMOLOGOUS SERIES:
The law of homologous series was formulated by N. I.
Vavilov in 1920. The Journal of Genetics published Vavilov’s
paper in 1922. This law established a parallel variability of
homologous characters in taxonomically near species. Now
it must be extended, including also a parallel variability of
similar homologous characters in taxonomically remote
species. Each similarity among biologic species is a cause
of homologous parallel variability in corresponding
characters. Vavilov showed that a variability of intraspecific
genes is controlled by the genotype of species. This
genotype is composed of stable species radical
(interspecific genes) and of labile intraspecific genes.
Vavilov’s basic concept of homologous variability retains its
viability. The law of homologous series is one of the
fundamental laws of genetics.

18. Gene Sanctuaries:
The genetic diversity is sometimes conserved under natural
habitat. In other words, areas of great genetic diversity are
protected from human interference. These protected areas in
natural habitat are referred to as gene sanctuaries. Gene sanctuary
is generally established in the centres of diversity or microcenter.
Gene sanctuary is Also Known As Natural Park or biosphere
reserve. India has setup its first gene sanctuary in the Garo Hills of
Assam for wild relatives of citrus. Efforts are also being made to
setup gene sanctuaries for banana, sugarcane, rice and Mango. In
Ethiopia gene sanctuaries for conservation of wild relatives of
coffee was setup in 1984. Gene sanctuaries have two main
advantages. Firstly, it protects the loss of genetic diversity caused
by human intervention. Secondly, it allows natural selection and
evolution to operate. There are two main drawbacks of gene
sanctuary. Firstly, entire variability of a crop species can not
conserved. Secondly , its maintenance and establishment is a
difficult task. It is a very good method of in Situ Conservation.

19. Gene Banks:
Gene bank refers to a place or organisation where germplasm
can be conserved in living state. Gene banks are also known as
germplasm banks. The germplasm is stored in the form of
seeds, pollen or in vitro cultures, or in the case of a field gene
bank, as plants growing in the field. Gene banks are mainly of
two types, viz: 1) Seed gene banks, and 2) Field gene banks.
These are briefly discussed below:
1. Seed Gene Bank:
A place where germplasm is conserved in the form of seeds is
called seed gene bank. Seeds are very convenient for storage
because they occupy smaller space than whole plants. However,
seeds of all crops can not be stored at low temperature in the
seed banks. The germplasm of only orthodox species (whose
seed can be dried to low moisture content without losing
variability) can be conserved in seed banks. In the seed banks,
there are three types of conservation, viz. 1) Short term, 2)
Medium term, 3) Long term.

20. Base collections are conserved for long term (50 years or
more) at 18 or 20 0C. Active collections are stored for short
term (3-5 years) at 5-10 0 C. The main advantages of gene
banks are as follows:
1. Large number of germplasm samples or entire variability
can be conserved in a very small space.
2. In seed banks, handling of germplasm is easy.
3. Germplasm is conserved under pathogen and insect free
environment.
There are some disadvantages of germplasm conservation
in the seed banks. These are listed below:
1. Seeds of recalcitrant species can not be stored in seed
banks.
2. Failure of power supply may lead to loss of viability and
there by loss of germplasm.
3. It requires periodical evaluation of seed viability. After
some time multiplication is essential to get new or fresh
seeds of storage.

21. 2. Field Gene Banks:
Field gene banks also called plant gene banks are
areas of land in which germplasm collections of
growing plants are assembled. This is also exsitu
conservation of germplasm. Those plant species that
have recalcitrant seeds or do not produce seeds
readily are conserved in field gene bank. In field gene
banks, germplasm is maintained in the form of
plants as a permanent living collection. Field gene
banks are often established to maintain working
collections of living plants for experimental
purposes. They are used as source of germplasm for
species such as coconut, rubber, mango, cassava,
yam, and cocoa. Field gene banks have been
established in many countries for different crops.

22. Name of Country
Crop Species for which Field Gene Bank is
Established
Malaysia Oil palm has been conserved on 500 hectares.
Indonesia
Earmarked 1000 hectares area for coconut and
other perennial crops.
Philippines
South East Asian germplasm of banana has
been conserved.
India
Global collection of coconut has been
conserved in Andaman ad Nicobar.
Field Gene Banks in Some Countries:

23. Field gene banks have some advantages and
disadvantages which are discussed below: There are
two main advantages.
1. It provides opportunities for continuous
evaluation for various economic characters.
2. It can be directly utilized in the breeding
programmes.
There are three main demerits of field gene banks as
given below:
1. Field gene banks can not cover the entire genetic
diversity of a species. It can cover only a fraction of
the full range of diversity of a species.
2. The germplasm in field gene banks is exposed to
pathogen and insects and some times is damaged by
natural disasters such as bushfires, cyclones etc.

24. 3.Meristem Gene Banks:
Germplasm of asexually propagated species can be conserved
in the form of meristem. This method is widely used for
conservation and propagation of horticultural species. In
vitro method can be used in two ways, first, for storage of
tissue under slow growth conditions. Second, for long term
conservation of germplasm by cryopreservation. In
cryopreservation, the tissues are stored at very low
temperatures i.e. at 196 0C in liquid nitrogen. At these
temperatures, all biological processes virtually come to a stop.
Based on status of Research Institutes, gene banks are again
of two types, viz. 1) National gene banks, and 2) International
or global gene banks . National gene banks are maintained by
each country and global gene banks are located in
International Crop Research Institutes/ Centres. In India,
gene banks are maintained by concerned crop research
institute of ICAR. National Bureau of Plant Genetic
Resources, New Delhi is also maintaining germplasm of

25. WHAT IS GENETIC EROSION:
Genetic erosion is a process where the
limited gene pool of an endangered
species diminishes even more when reproductive
individuals die off before reproduce low
population. The term is sometimes used in a
narrow sense, such as when describing the loss of
particular alleles or genes, as well as being used
more broadly, as when referring to the loss of a
phenotype or whole species.

26. Genetic erosion occurs in plant species for the
following reasons:
1.Loss of habitat is a cause of genetic erosion here as well.
2.Overgrazing an area can lead to loss of plant species; so also
the spoiling of an environment by land clearing or chemical
dumping or over-zealous construction.
3.Replacing local varieties of plants with those that wouldn't
occur there naturally, like plants from another area
or genetically modified (GM) plants, can also lead to genetic
erosion.
4.Modern agriculture is also responsible to a large extent for
loss of genetic diversity. Farmers tend to grow a limited
number of commercial crop varieties or GM crops, enforcing a
uniformity in farming, and so there has been a noticeable
reduction in the many crop varieties that were seen with
traditional farming.

27. EXTINCTION:
Extinction is the end of an organism or
of a group of organisms (taxon),
normally a species. The moment of
extinction is generally considered to be
the death of the last individual of the
species, although the capacity to breed
and recover may have been lost before
this point.

28. List of extinct animals of India
This is a list of extinct animals of India.
1.Bharattherium
2.Exaeretodon
3.Gigantopithecus
4.Hyperodapedon
5.Indian aurochs (Bos primigenius namadicus)
6.Indian Cheetah
"Sivatherium"
6.Pink Headed Duck

29. Irish Elk (5,200 B.C.)
Some pictures are:

30. Quagga
. Great Auk

31. . Pinta Island Tortoise

32. Woolly Mammoth

33. Smilodon

34. Introgression:
It is the genetic modification of one species by
another through hybridization and repeated
backcrossing. Introgression is important in the
evolution of flowering plants. It is also important
in plant breedingwhere a desirable trait can be
transferred from wild to crop species.

35. THANK YOU……