this slide animation and videos work mainly in power point 2013 version.the slide contain aquatic mammals and their evolutions.mainly evolutions and their adaptive mechanisms are also listed

2. Introduction
 Mammals are primarily terrestrial animals .
 Some of them have wonderfully adapted for a secondary
aquatic life.
 Based on the relation to water and the degree of aquatic
adaptations aquatic mammals are grouped into
1.Completely aquatic mammals
2.semi-aquatic or amphibious mammals

3. Semi aquatic animals
morphological modifications
 Sleek & slender body
 Dense &soft fur (hairy coat)
 Elongated snout
 Small ear lobes
 Flat tail
 Webbed hands & feet
 Sub cutaneous fat

4. Semi aquatic mammals
Group
 Monotremata
 Marsupialia
 Rodentia
 Artiodactyla
 Pinnipidia
Examples
 Ornithorhynchus
 Chironectes
 Beavers , Musk rats
 Hippopotamus
 Walruses , otters , seals ,
sea lions

5. Monotremata : egg laying mammals
Ornithorhynchus

8. Poison gland

9. Marsupialia :
Chironectes

11. Rodentia :long incisors that grow continuously
Beavers

13. Musk rats

14. Artiodactyla : hooved mammals
Hippopotamus

16. Pigmy Hippopotamus

17. Pinnipidia : carnivorous aquatic mammals
Walruses

18. Otters

20. Seals

21. Sea lion

23. Sea lion Seal

24. Completely aquatic mammals
Group
 Cetacea
 Sirenia
Examples
 Whales , dolphins ,
porpoises
 Dugongs , manatees

25. Cetacea : whale like mammals
Baleen whale

28. Blue whale

29. Sperm whale

30. Killer whale

31. Dolphins

33. Porpoises

36. Sirenia : aquatic herbivorous mammals
Dugongs (sea cows)

37. Manatees

38. All secondarily aquatic mammals are believed
to have evolved from terrestrial ancestors.
A great disadvantage of all aquatic mammals
is retention of the lung breathing habit

41. Aquatic adaptations
1. Modification of body contour
2. Integumentary modifications
3. Locomotor adaptations
4. Skeletal modifications
5. Modifications in the digestive system
6. Respiratory modifications
7. Modifications of sense organs
8. Reproductive modifications

42. Modification of body contour
 Most aquatic mammals have a tapering &
streamlined body-----only least resistance in
swimming
 Elongation of skull
 Reduction of zygomatic arches
 Development of cylindrical chest
 Reduction of projecting structures------ hind limbs ,
pinnae , scrotum etc…..

43. Integumentary modifications
 The modifications mainly loss of hair & skin glands & the formation of
blubber (fatty layer of adipose tissue , beneath the epidermis ---thick
coat )
 Blubber serve as a heat insulator and there by prevents the loss of
body heat & maintains a constant body temperature.
 Reduce specific gravity of the body in the water
 Act as shock absorber to absorb the hydraulic pressure during deep
diving
 Skin surface has become smooth by the loss of hair
 Hair represented by a few bristles around the mouth (exception in
white whales) present in whales & sea cows

45. Locomotor adaptations
1. Elongation of the body
2. Reduction or loss of hind limbs
3. Formation of dorsal fin , tail flukes & flippers or
swimming paddles
4. Hyperdactyly (formation of extra fingers) &
hyperphalangy (formation of extra phalanges)

46. Modification , reduction and loss of hind limbs
 In cetaceans & sirenians hind limb altogether absent
, since tail , fore limb & dorsal fin are mainly involved
in locomotion.
 Ornithorhynchus and chironectes ,fore limbs & hind
limbs have webbed digits.
 In pinnipidians hind limbs are enclosed by skin ,
forming oar like structures

47. Formation of dorsal fin & tail flukes
 Tail of aquatic mammals , in general is horizontally
flattened , forming a sort of caudal fin
 In cetaceans , the flattened tail is provide with lateral
expansions of the skin , called tail flukes .
 The movement of tail & tail flukes help to forward &
vertical movement of an organism.
 Dorsal fin & dorsal fluke, which act as a rudder or keel
in swimming

49. Formation of flippers
 In semi aquatic mammals fingers are webbed .
 In completely aquatic form fore limbs are modified
into swimming paddles or flippers.
 A flippers consist of an internal support of fused
bones , covered by skin
 Flippers act as balancers & stabilizers in swimming

50. Hyperdactyly & Hyperphalangy
 Flippers are characterized by hyperdactyly and
hyperphalangy (development of extra fingers & extra
phalanges)
 This gives them sufficient strength and support and
increases their surface area

51. Skeletal modifications
 Endoskeleton is lighter by the presence of oil inside bones
 Dorso ventrally flattened cranial region
 Elongated facial region for catching prey
 Vertebrae are simple with well developed neural spines
and transverse process --- for the attachment of muscles
 Cervical vertebrae are fused to form a small solid bone----
--- neck region reduced

52.  Ribs are movable & dorsally attached
this enhance the lung capacity and also
increases the thoracic cavity backward for flotation

53. Modifications in the digestive system
 In fully aquatic jaws are used only for catching the
prey & not for mastication
 Mastication is practically absent in oral cavity
 Salivary glands are very much reduced
 Stomach of mostly aquatic mammals has
chambered & specialized for crushing and digesting
the food

54.  Teeth are simple and dentition is homodont and
monophyodont
 In toothed Whales teeth are quite numerous (more
than 250 )
 In baleen whales teeth are present only embryo in
the adult they will be replaced by numerous baleen
plates or whalebones
these are arranged on upper jaw in to transverse
rows , baleen plates act as strainers for filtering
planktonic food

55. Respiratory modifications
 Respiratory system of fully aquatic mammals is highly
modified for a life in water.
 External nostrils are valvular & located far back on
the top of the head
 Dorsal position of the nostril enables the animal to
inhale atmospheric air ,without raising head
 Nostrils are valvular , they can be closed during
under water stay
 Epiglottis has become tubular, elongated

57. Blow hole

58. Storage of large quantity of air for underwater stay
 Modification of lungs
 High concentration of myoglobin in muscles
 Storage large volume of oxygen in rete mirabile
 Lungs are large , highly elastic & non lobular with
high storage capacity
 Diaphragm is oblique & this makes the thoracic
cavity sufficiently large for maximum expansion of
lungs.
 30 minute survive in under water

61. Modification of sense organs
 Eyes ::::::::::1 )relatively smaller in size
2 ) cornea is flat & lens is reduced
3 ) nictitating membrane , lacrimal
gland ,lacrimal ducts are absent
4 ) during under water stay eyes are
protected by a fatty secretion from
Harderian gland

62.  Ear :::::::: 1) external auditory opening is small
2) auditory canal is filled with secretion
3) Acoustic system is reduced

63. Reproductive modifications
 Testes are intra abdominal in position & scrotal sacs
are absent
 The period of gestation is considerably long (more
than one year) so that young ones will be much
grow and nearly one-third of the mother’s size when
born

64. Development of young ones Can be divided in 3 category
Neoformations : development of tail flukes
dorsal fin , baleen plates,
, harderian gland etc..
Degenerations : loss of ancestral structures , loss
of hair , hind limbs , finger nails ,
pinnae , cutaneous glands ,
lacrimal glands , nictitating
membrane , scrotum etc…

65. Modifications : streamlined body ,
dorsal valvular nostril
blubber
rete mirabile
highly oblique diaphragm
flippers
simple bilobed liver
non lobular lungs
tubular & elongated epiglottis
chambered stomach
elongation of skull
hyperdactyly ,hyperphalangy
reduced sternum
shortening fusion of cervical vertebrae etc…