Endemism refers to species exclusively found in a particular region and absent elsewhere, stemming from evolutionary isolation. There are various types of endemics such as continental, provincial, and neo-endemics, each defined by their restricted distributions and origins. Factors like environmental isolation, mutation, and natural crossing contribute to endemism, with extinction categorized into natural, mass, and anthropogenic forms, largely driven by human activities.

1. (C) ENDEMIC DISTRIBUTION OR ENDEMISM
ENDEMIC DISTRIBUTION, OR ENDEMISM, IS THE RESTRICTED DISTRIBUTION OF SOME GENERA OR GROUPS OF
PLANTS ONLY IN A PARTICULAR AREA AND ARE ALTOGETHER ABSENT ANYWHERE ELSE IN THE WHOLE
WORLD.
IT IS AN EVOLUTIONARY PHENOMENON IN WHICH ISOLATION LEADS TO THE DEVELOPMENT OF UNIQUE
SPECIES THAT ARE CONFINED EXCLUSIVELY TO A PARTICULAR AREA.
THUS, ENDEMIC SPECIES, OR ENDEMICS, ARE THOSE SPECIES WHICH ARE RESTRICTED ABSOLUTELY TO A
SPECIFIC AREA, SUCH AS A LOCALITY, REGION, COUNTRY, ISLAND, OR MOUNTAIN RANGE, AND ARE NOT
SEEN ANYWHERE ELSE.
ENDEMIC SPECIES HAVE LITTLE OR NO VARIABILITY DUE TO POOR MUTABILITY AND THEY ARE ADAPTED ONLY
TO A PARTICULAR ENVIRONMENT.
THE CONCEPT OF ENDEMIC DISTRIBUTION OF PLANTS WAS FIRST PUT FORWARD BY A.P. DE CANDOLLE
(1813). ENGLER (1882) SUGGESTED THAT ENDEMICS ARE OF TWO TYPES, PALAEOENDEMICS AND
INDIGENOUS OR NATIVE ENDEMICS.
PALAEO-ENDEMICS ARE THE SURVIVORS OF AN ANCIENT GROUP
NATIVE ENDEMICS ARE THE PRODUCTS OF ISOLATIONS, EXCLUSIVELY CONFINED TO A PARTICULAR LOCALITY.

2. KINDS OF ENDEMICS
(i) CONTINENTAL ENDEMICS
THE ENDEMICS THAT ARE RESTRICTED TO A PARTICULAR CONTINENT ALONE.
(II) PROVINCIAL, REGIONAL OR LOCAL ENDEMICS
THE ENDEMICS THAT ARE RESTRICTED TO A SMALL AREA OR LOCALITY, SUCH AS A MOUNTAIN
PEAK, HILL VALLEY, ISLAND, ETC.
(III) RELIC ENDEMICS
THESE ARE THE SURVIVORS OF A WIDELY DISTRIBUTED ANCIENT GROUP OF THE REMOTE PAST,
NOW RESTRICTED TO A SPECIFIC AREA. SO, THEY CAN BE REGARDED AS LIVING FOSSILS. RELIC
ENDEMICS ARE ALSO CALLED EPIBIOTICS. EXAMPLES ARE GINKGO BILOBA (RESTRICTED TO A
SMALL AREA IN CHINA AND JAPAN), SEQUOIA SEMPERVIRENS (CONFINED TO THE COASTAL
VALLEYS OF CALIFORNIA), METASEQUOIA (CONFINED TO A SINGLE VALLEY IN CHINA), AGATHIS
AUSTRALIS (CONFINED TO CHINA), ETC.

3. (IV) PALAEO-ENDEMICS
THESE ARE THE PLANT SPECIES WHICH ORIGINATED IN THE REMOTE GEOLOGICAL PAST AND REMAINED RESTRICTED TO
A SMALL AREA OF FAVOURABLE CONDITIONS. THEY ARE ADAPTED ONLY TO A PARTICULAR ENVIRONMENT AND ARE
UNABLE TO ESTABLISH THEMSELVES IN A NEW ENVIRONMENT.
(V) NEO-ENDEMICS
RECENTLY EVOLVED PLANT SPECIES WHICH DID NOT GET ENOUGH TIME FOR EXTENSIVE DISTRIBUTION THROUGH
MIGRATION AND ARE HENCE REMAINED RESTRICTED TO SPECIFIC AREAS.
NEOENDEMICS OF LOWER TAXONOMIC RANK ARE CALLED MICROENDEMICS.
NEOENDEMICS SHOW GREAT VARIABILITY, HAVE MANY BIOTYPES, GROW IN DIVERSE HABITATS, AND HAVE WIDE
TOLERANCE.
SOME NEO-ENDEMIC FORMS OF INDIA ARE MECANOPSIS, CATENARIA, BUTEA, CAESULIA, ELETTARIA REPENS, PIPER
LONGUM, SHOREA ROBUSTA, ETC.
(VI) PROGRESSIVE ENDEMICS
THE ENDEMIC SPECIES WHICH HAVE NOT SPREAD FROM THE AREA OF THEIR ORIGIN. RECENTLY EVOLVED PROGRESSIVE
ENDEMICS OF INDIA INCLUDE HIERACIUM (FOUND IN THE MOUNTAIN DISTRICTS OF INDIA), LASIOCOCCA AND
DILLOCERAS (FOUND IN EASTERN HIMALAYAS), SAXIFRAGA IMBRICATA, PRIMULA MINUTISSIMA AND KORBESIA DUTHEI
(FOUND IN WESTERN HIMALAYAS), ETC.

4. VII) CONSERVATIVE ENDEMICS
THE ENDEMICS WHICH WERE FORMERLY WIDESPREAD BUT NOW WITHDRAWN TO A PARTICULAR
AREA WHERE ENVIRONMENTAL CONDITIONS ARE FAVOURABLE AND COMPETITION IS LESS
SEVERE. TAXODIUM DISTICHUM IN THE SOUTH EAST OF NORTH AMERICA IS AN EXAMPLE.
(VIII) PSEUDO-ENDEMICS
PLANTS WHICH ORIGINATE AS MUTANTS IN LOCAL POPULATIONS. THEY CANNOT COMPETE
SUCCESSFULLY AND HENCE DISAPPEAR GRADUALLY.

5. FACTORS RESPONSIBLE FOR ENDEMISM
THE MAJOR FACTORS WHICH CAUSE OR CONTRIBUTE TO ENDEMISM ARE GEOGRAPHICAL AND
ENVIRONMENTAL ISOLATION, MUTATION, AND NATURAL CROSSING BETWEEN CLOSELY RELATED
PLANTS GROWING UNDER FAVOURABLE CONDITIONS.

6. HYPOTHESES ABOUT ENDEMISM
(a) RIDLEY'S EPIBIOTIC HYPOTHESIS
THE EPIBIOTIC HYPOTHESIS OF RIDLEY (1922) HOLDS THAT ENDEMICS ARE ONLY THE RELICS OR EPIBIOTICS
(LAST SURVIVORS) OF A ONCE FLOURISHING AND WIDESPREAD GROUP, NOW UNDER THE THREAT OF
EXTINCTION.
THEY PERSIST IN ISOLATED AREAS OR SAFE SURVIVAL POCKETS AND ARE UNABLE TO SPREAD ANY FURTHER
SIMPLY BECAUSE THEY ARE NOT ENDOWED WITH EFFECTIVE MEANS OF DISPERSAL FOR CROSSING BARRIERS.
THEY ARE ESPECIALLY ABUNDANT IN ANCIENT ISLANDS AND MOUNTAIN MASSIFS. FOR EXAMPLE, NEARLY
72% OF THE FLORA OF NEW ZEALAND AND ABOUT 85% OF THE FLORA OF ST. HELENA ARE ENDEMIC.
THE ADVOCATES OF RIDLEY'S HYPOTHESIS CITE NUMEROUS RELICS FOUND IN THE NORTHERN TEMPERATE
REGION. FOR EXAMPLE, THE NOW ENDEMIC SEQUOIA SEMPERVIRENS OF THE CENTRAL VALLEY OF
CALIFORNIA AND OREGON, AND S.GIGANTUS OF SIERRA NEVEDA WERE EXTENSIVELY DISTRIBUTED IN THE
CRETACEOUS AND TERTIARY TIMES.
SO, ACCORDING TO THIS VIEW, TREE FERNS CAN BE REGARDED AS RELIC ENDEMICS, SINCE HEY ARE NOW
RESTRICTED ONLY TO A FEW AREAS IN THE WHOLE WORLD.

7. (B) AGE AND AREA HYPOTHESIS OF WILLIS
THE AGE AND AREA HYPOTHESIS WAS PROPOSED BY WILLIS (1915) ON THE BASIS OF HIS EXTENSIVE STUDIES ON THE
GEOGRAPHICAL DISTRIBUTION OF CERTAIN PLANT SPECIES OF THE TROPICS.
i) ENDEMICS ARE NOT MERE RELICS OF THE BY-GONE AGES, BUT ARE INSTEAD SPECIES OF RELATIVELY RECENT ORIGIN
(NEO-ENDEMICS).
(II) THERE IS A DIRECT CORRELATION BETWEEN THE AREA OCCUPIED BY A SPECIES AND ITS EVOLUTIONARY ANTIQUITY.
(III) THE AREA OCCUPIED BY A SPECIES WHICH EVOLVED EARLIER WILL BE LARGER THAN THE AREA OCCUPIED BY A SPECIES
WHICH APPEARED LATER IN THE EVOLUTIONARY SEQUENCE.
(IV) THE AREA OCCUPIED BY A SPECIES INCREASES WITH ITS AGE. WHETHER THIS INCREASE IS DIRECTLY PROPORTIONAL TO THE
AGE IS NOT CLEAR.
(V) THE FREQUENCY OF A SPECIES OVER AN AREA IS DIRECTLY PROPORTIONAL TO ITS EVOLUTIONARY AGE.
(VI) SMALL AREA OF DISTRIBUTION, OR A VERY LOCALISED DISTRIBUTION OF A SPECIES, INDICATES ITS RECENT ORIGIN OR
YOUNG AGE, AND A LARGE AREA OF DISTRIBUTION INDICATES ANCIENT ORIGIN OR ADVANCED AGE.
(VII) NEWLY EVOLVED SPECIES NATURALLY WILL HAVE A SMALL RANGE OF DISTRIBUTION. THIS IS BECAUSE THE EVOLUTIONARY
TIME AT THEIR DISPOSAL AND THE DEGREE OF THEIR ADAPTIVE MODIFICATIONS AND ECOLOGICAL AMPLITUDE ARE NOT
SUFFICIENT FOR SPREADING. IN OTHER WORLDS, THEY DID NOT GET ENOUGH TIME TO DEVELOP ADAPTIVE MODIFICATIONS
AND ECOLOGICAL AMPLITUDE FOR EXPANDING THE RANGE OF THEIR DISTRIBUTION. WILLIS HAS QUOTED THE DISTRIBUTION OF
SEVERAL EXAMPLES, SUCH AS IMPATIENS, PRIMULA, GENTIANA, RHODODENDRON, COLEUS, ETC. TO ESTABLISH HIS HYPOTHESIS.

8. VICARISM
VICARISM, OR VICARIANCE, IS THE GEOGRAPHICAL SEPARATION OF A SPECIES, RESULTING IN TWO CLOSELY
RELATED SPECIES OR A SPECIES PAIR ONE OF WHICH WOULD BE THE GEOGRAPHICAL COUNTERPART OF THE
OTHER.
IN VICARIOUS DISTRIBUTION, ONE MEMBER OF A SPECIES PAIR (I.E. TWO CLOSELY RELATED SPECIES DERIVED
FROM A COMMON ANCESTOR) WILL BE GEOGRAPHICALLY REPLACED BY THE OTHER.
THERE ARE MANY ANIMALS AND HERBACEOUS PLANTS WITH VICARIOUS DISTRIBUTION BETWEEN N.AMERICA
AND EUROPE.
RAK (1993) HAS SUGGESTED A VICARIOUS RELATIONSHIP BETWEEN NEANDERTALS AND EARLY MODERN
HUMANS.
HE PROPOSED THAT MODERN HUMANS INHABITED LEVANT DURING THE WARMER PHASE WHEN THE REGION
WAS MORE CLOSELY LINKED TO N.AFRICA, AND NEANDERTALS INHABITED THE REGION WHEN COLDER
EUROPEAN CLIMATE PREVAILED.
EACH POPULATION EITHER MIGRATED OUT OF THE REGION OR BECAME EXTINCT WHEN THE REGIONAL
CLIMATE CHANGED.

9. EXTINCTION
SPECIES EXTINCTION IS THE TOTAL EXTERMINATION OR DISAPPEARANCE OF SPECIES.
SPECIES BECOME EXTINCT WHEN THEY ARE NO LONGER ABLE TO SURVIVE IN CHANGING
CONDITIONS, OR AGAINST SUPERIOR COMPETITIONS.
EXTINCTION IS OF TWO MAIN KINDS, TOTAL EXTINCTION AND LOCAL EXTINCTION OR
EXTRIPATION.
IN TOTAL EXTINCTION, THERE ARE NO SURVIVING MEMBERS OF THE SPECIES ANYWHERE IN THE
WORLD.
BUT IN LOCAL EXTINCTION, A SPECIES CEASES TO EXIST ONLY IN SOME AREAS, AND IT MAY EXIST
IN OTHER AREAS. THE ALREADY EXISTING SPECIES ARE CALLED EXTANT SPECIES.
THE EXTANT SPECIES WHICH ARE UNDER THE SEVERE THREAT OF EXTINCTION, OR ARE ON THE
VIRGE OF EXTINCTION, ARE CALLED THREATENED SPECIES.

10. KINDS OF SPECIES EXTINCTION
BASED ON THE CAUSE OF EXTINCTION, THREE TYPES OF SPECIES EXTINCTION CAN BE RECOGNIZED, NAMELY
NATURAL EXTINCTION, MASS EXTINCTION AND ANTHROPOGENIC EXTINCTION.
(a) NATURAL EXTINCTION
THIS IS THE SPONTANEOUS ELIMINATION OF SPECIES BY NATURE.
NATURE WILL ELIMINATE THOSE SPECIES WHICH ARE UNFIT OR UNSUCCESSFUL IN A CHANGING ENVIRONMENT,
OR IN THE STRUGGLE FOR EXISTENCE.
NATURAL EXTINCTION IS A BIOLOGICAL PHENOMENON.
IT OCCURS AS A PART OF ORGANIC EVOLUTION AND ECOLOGICAL SUCCESSION.
IN A CHANGING ENVIRONMENT, OR IN THE STRUGGLE FOR EXISTENCE, THE LEAST ADAPTED SPECIES DISAPPEAR
AND THE MORE ADAPTED ONES SURVIVE.
IN OTHER WORDS, NATURE ELIMINATES THE UNFIT OR UNSUCESSFUL SPECIES AND PRESERVES THE FITTEST ONES.
THE NATURAL ELIMINATION OF SPECIES, OCCURRING IN THE EVOLUTIONARY HISTORY OF LIFE, IS CALLED
BACKGROUND EXTINCTION.
IT IS A VERY SLOW PROCESS.

11. THE MAIN CAUSES FOR NATURAL EXTINCTION FALL UNDER FOUR MAJOR CATEGORIES, NAMELY
POPULATION RISK, ENVIRONMENTAL RISK, GENETIC RISK, AND NATURAL CATASTROPHES.
1. POPULATION RISK: THIS INCLUDES ABNORMAL VARIATIONS IN NATALITY AND MORTALITY.
THESE VARIATIONS CAUSE THE LOW-ABUNDANCE SPECIES TO GO EXTINCT. THIS IS ESPECIALLY
TRUE THE SPECIES WHICH CONSIST OF ONLY A SINGLE POPULATION IN ONE HABITAT OR AREA.
2. ENVIRONMENTAL RISK: THIS INCLUDES NATURAL VARIATIONS IN THE ABIOTIC AND BIOTIC
ENVIRONMENTS. THESE VARIATIONS, IN ALL PROBABILITY, MAY LEAD TO THE EXTINCTION OF
ISOLATED AND RARE SPECIES.
3. GENETIC RISK: THIS INCLUDES THE HARMFUL GENETIC VARIATIONS IN A SMALL POPULATION DUE
TO UNFAVOURABLE MUTATION, GENETIC DRIFT, ETC. SUCH VARIATIONS WOULD ADVERSELY AFFECT
THE SURVIVAL VALUE AND WOULD MAKE THE POPULATION VALUERABLE TO LOCAL EXTINCTION.
4. NATURAL CATASTROPHES: NATURAL CATASTROPHES, SUCH AS FLASHFLOODS, WILD FIRES,
STORMS, EARTHQUAKES, VOLCANIC ERUPTIONS, ETC. OFTEN CAUSE THE LOCAL EXTINCTION OF
MOST FORMS OF LIFE.

12. (B) MASS EXTINCTION
THIS IS THE LARGE-SCALE OR MASSIVE GEOLOGICAL EXTINCTION OF MANY PROMINENT SPECIES
AFTER MANY MILLION YEARS OF SUCCESSFUL AND WIDESPREAD EXISTENCE.
THE POPULAR NOTION IS THAT GEOLOGICAL CATASTROPHES ARE RESPONSIBLE FOR SUCH
EXTINCTION EPISODES.
THE REASON MIGHT BE THAT THE GAPS AND DISCONTINUITIES IN THE FOSSIL RECORD OFTEN
COINCIDE WITH MASS EXTINCTIONS.
MASS EXTINCTIONS HAVE AFFECTED MANY UNRELATED GROUPS OF ORGANISMS IN A VARIETY
OF LIVING ZONES.
ALSO, THEY HAVE OCCURRED MOSTLY AT THE ENDS OF THE CAMBRIAN, ORDOVICIAN,
DEVONIAN, PERMIAN, TRIASSIC AND CRETACEOUS PERIODS

13. C) ANTHROPOGENIC EXTINCTION
THIS IS THE EXTINCTION OF SPECIES, COMPLETED IN A SHORT PERIOD OF TIME DUE TO HUMAN
ACTIVITIES.
IT MAY RESULT IN THE DRASTIC DEPLETION OF BIODIVERSITY, UPSETTING THE BALANCE OF
NATURE.
MAN HAS LONG BEEN RESPONSIBLE FOR THE EXTINCTION OF MANY SPECIES AND THE DEPLETION
OF BIOLOGICAL RESOURCES.

14. CAUSES OF ANOTHROPOGENIC SPECIES EXTINCTION
(i) ALTERATION, DEGRADATION REDUCTION AND LOSS OF NATURAL HABITATS DUE TO HUMAN
SETTLEMENT, GRAZING, AGRICULTURE, COMMERCIAL PLANTATIONS, INDUSTRIALIZATION,
URBANIZATION, MINING, AND CONSTRUCTION OF DAMS, ROADS, RAILWAYS, ETC.
DESTRUCTION OF TROPICAL FORESTS, CORAL REEFS, ESTUARIES, MARSHES, LAKES AND OTHER
BIOLOGICALLY RICH ECOSYSTEMS AMOUNTS TO ELIMINATE THOUSANDS OF SPECIES.
HABITAT DESTRUCTION ELIMINATES NOT ONLY PROMINENT SPECIES BUT ALSO MANY OBSCURE MEMBERS
OF A COMMUNITY ABOUT WHICH LITTLE IS KNOWN.
IF THE CURRENT RATE OF HABITAT DESTRUCTION GOES ON UNABATED, MANY THOUSAND SPECIES MAY
BE LOST IN A FEW HUNDRED YEARS TO COME.
(II) INTRODUCTION OF EXOTIC SPECIES TO NEW AREAS.
THIS OFTEN INCREASES THE CHANCES FOR COMPETITION, PREDATION, HABITAT DEGRADATION,
TRANSMISSION OF PARASITES AND DISEASES, ETC. THIS ADVERSELY AFFECTS THE SURVIVAL OF NATIVE
SPECIES AND LEADS TO THEIR ULTIMATE EXTERMINATION.
(III) OVER-EXPLOITATION OF BIOTIC RESOURCES BY MANKIND.