The document discusses adaptive radiation in mammals, defining it as the rapid diversification of an ancestral species into various forms and niches. It explores causes, types, and characteristics of adaptive radiation, along with the rise and evolution of mammals, particularly after the extinction of dinosaurs. The significance of adaptive radiation is highlighted, emphasizing its role in creating diverse species and traits, while suggesting the potential for future adaptive radiation in humans.

1. ADAPTIVE RADIATION IN MAMMALS
SAMBIT KUMAR DWIBEDY
ROLL NO-8
PG 1ST YEAR

2. CONTENTS
1. Introduction
2. What is Adaptive Radiation?
3. Causes
4. Types
5. Characteristics
6. Mechanism
7. The rise of Mammals
8. Examples of adaptive radiation in Class-Mammalia
9. Significance
10.Conclusion

3. INTRODUCTION
“Where do new species come from?” This is the key question that biology have
been asking for more than 200 years.
Charles Darwin Gave us part of the answer in his explanation of natural selection.
Now we know that new species are formed by evolution .Evolution occur in 2
different patterns.
Successive Speciation
Adaptive Radiation

4. WHAT IS ADAPTIVE RADIATION?
First use of term Adaptive Radiation-Osborn
1. It is the evolutionary divergence of members of a single phyletic line into a
series of different niches. ( Mayer,1931)
2. Adaptive radiation is a process in which organism diversify rapidly from an
ancestral species into a multitude of new forms. (Smith, 1976)

5. LAW OF ADAPTIVE RADIATION
An isolated region, if large and sufficiently varied in its topography, soil, climate and
vegetation, will give rise to a diversified fauna from primitive types. Branches will
spring off in all directions to take advantage of every possible opportunity of
securing food.”

6. CAUSES OF ADAPTIVE RADIATION
1. Entry into an adaptive zone by :-
Evolution of a key innovation
Invasion into a new habitat
Extinction of competition
(Simpson)
2. Ecological Opportunity
(Dolph Schlutler,2002)
2. Mass extinction

7. THE AMNIOTIC EGG:
 Perhaps one of the
greatest key
innovations of all
time

8. ANOTHER KEY INNOVATION:
WINGS

9. TYPES
3 types
1. General Adaptive Radiation
2. Adaptive radiation by environmental change
3. Adaptive radiation in Archipelagos

10. CHARACTERISTICS
1. Common ancestry
2. Phenotype –Environment correlation
3. Trait utility
4. Rapid speciation

11. MECHANISMS
ECOLOGICAL OPPORTUNITY
RELEASE FROM NATURAL SELECTION
ECOLOGICAL RELEASE
RAPID SPECIATION & MORPHOLOGICAL
DIVERSIFICATION
ADAPTIVE RADIATION

12. THE RISE OF MAMMALS
 Mammals are amniotes that have hair and mammary glands.
 5300 species in class Mammalia
 Mammals evolved from synapsids.
 Mammals originated in the Mesozoic era. They were mouse like
with quadrupedal locomotion.
 Mesozoic Mammals remained small till Cretaceous due to the
presence of Dinosaurs.
 65 million years ago , after the extinction of Dinosaurs ,in the early
Coenozoic era the number and diversity of mammals exploded.

13. SMALL SIZED MAMMALS IN THE
MESOZOIC ERA IN THE PRESENCE
OF DINOSAURS

14. ADAPTIVE RADIATION IN MAMMALS
ANCESTRAL
MAMMAL
MONOTREMES
EUTHERIANSMARSUPIALS

15. ADAPTIVE RADIATION IN PLACENTAL MAMMAL BASED
ON LOCOMOTION
The limb structure (mode of locomotion) of placental mammal provides an
classical example of adaptive radiation.
The ancestor of the present day placental mammal was a five-toed short legged
terrestrial insectivore.
From such stem mammals, various modern types of mammals have evolved by the
modification of limbs
• Flying placental mammal
• Climbing placental mammal
• Swimming placental mammal
• Cursorial placental mammal
• Fussorial placental mammal

18. AUSTRALIAN MARSUPIALS DEMONSTRATE AN
ADAPTIVE RADIATION IN THE ABSENSE OF
COMPETITIVE INTERACTIONS WITH PLACENTAL
PLACENTAL MAMMALS
KANGAROO
WOMBAT

19. ADAPTIVE RADIATION IN MARSUPIALS
ANCESTRAL
MARSUPIAL
GRAZING
(WALLABIES)
CURSORIAL
(TASMANIAN
WOLF)
ANT-EATING
(BANDED
ANTEATER)
ARBOREAL
(KOALA)
VOLANT
(FLYING
PHALANGER)
FOSSORIAL
(MOLE)
INSECTIVOROUS
(BANDICOOT)
CARNIVOROUS
(NATIVE CAT)

20. GRAZING WALLABIES
INSECTIVOROUS BANDICOOT
CARNIVORUS NATIVE CAT
BANDED ANT-EATER

21. ARBOREAL KOAALA
CURSORIAL TASMANIAN WOLF
FLYING PHALANGER
FOSSORIAL MARSUPIAL MOLE

22. FUTURE ASPECTS
There is a single living species of genus Homo. Adaptive radiation in
humans has not occurred yet but there is a chance of occurrence of
adaptive radiation in humans when the homo species will be diverged
into different lineages.
CHINA CARRIBEAN INDIAN AFRICAN AUSTRALIA

23. SIGNIFICANCE
1.Diversification of organisms
2.Origin of new species
3.Acquisition of novel adaptive traits
4.Less competition
5.Less chance of extinction

24. CONCLUSION
The highly advanced mammals are the result of adaptive radiation.
Much research has been done on adaptive radiation of Mammals due to its
dramatic effects on mammalian diversity. However more research is needed
especially to fully understand the many factors affecting adaptive radiation.

25. REFERENCE
1.Rastogi , V. B. “Evolutionary biology”,Kedar Nath Ram Nath Publication,(U.P) India, pp. 333-347.
2. Dobzhansky , T. (1973) “Evolution”, Surjeet Publication, Delhi, India, pp.150-170.
3.Chattopadhyay S.,(2008).’Evolution Adaptation & Ethology’ pp.332-338.
4.Schluter, D. (1996) “Ecological causes of adaptive radiation.” American Naturalist 148:540-564.
.
5..Simpson, G. G. (1953). The Major Features of Evolution. New York: Columbia University Press.
6..Meyer J. R., Schoustra S., Lachapelle J.and Kassen R. (2011).
Overshooting dynamics in a model adaptive radiation. Proceedings of the Royal Society PP.392–
398.
7..Losos, J. B. (2010) “Adaptive radiation, ecological opportunity and evolutionary Determinism”
American Naturalist 175(6):623-39