How animals adapt to different environments

1. Adaptations
Adaptations include adjustments by which an organism
accommodates itself to its environment.
These may occur by natural selection.
 Three types of adaptations of animals
1. Aquatic adaptations
2. Volant adaptations
3. Desert adaptations.

2. Aquatic Adaptations
Aquatic animals.
Aquatic adaptations occur in those animals which live in
water habitat
e.g. fresh, brackish or sea water.
Based upon the phylogenetic history of the aquatic
animals, following two types of hydrocoles have been
recognized :

3. • 1. Primary aquatic animals.
The primarily aquatic animals
Those in which the phylogenetic history is restricted to water as habitat.
• 2. Secondary aquatic animals.
These hydrocoles which have record of terrestrial life
• In their phylogeny they are descended from ancestors which led a life on
land
• Secondary aquatic animals are lung-breathers, mainly amphibious
vertebrates, which through stress of circumstances such as inhospitable
lands, where food was scarce or severe competitions were forced to return
once more.
• Adaptations
 Aquatic Adaptations
 Volant Adaptations
 Desert Adaptations

4. A. Primary Aquatic Adaptations
1. Body contour.
The form of body depends upon the habits of life.
• The majority of fixed and partly sedentary forms have
radially symmetrical body forms, e.g., sponges (Sycon,
Euplectella, Hyalonema, etc.,), Hydra, Obelia, Aurelia,
Metridium (sea anemone), echinoderms such as
Holothuria, Echinus,
• The active locomotor type have fusi form, spindle-
shaped elongated and wormlike bodies.
• The spindle form is the characteristic of fishes and
wavy, worm-like form is found in the annelids (Nereis).

5. 2. Swimming organs.
• Some aquatic animals float passively and do not
possess much powers of movement, e.g.,
dinoflagellates (Protozoa).
• The medusae and most siphonophores move by
alternative contraction and expansion of their
subumbrellar side.
• Organs for active swimming exist in arthropods
(e.g., prawn or Palaemon), annelids

6. • 3. Respiration.
The primary aquatic animals are able to respire inside the
water, without the need to come up to the surface.
The exchange of respiratory gases takes place between
the blood of these animals and the water outside.
There are two methods of aquatic breathing :
1. through diffusion through general body surface, e.g.,
protozoans, coelenterates and planktonic larvae, and
2. with the help of special organs called branchia or gills,
e.g., prawns, and other crustaceans; Unio, Pila and
other molluscs ;

7. 4: Air bladder.
• Advanced bony fishes contain air bladder (or swim
bladder) which serve as an accessory respiratory
organ and hydrostatic organ.
• Air bladder is a hollow outgrowth of the alimentary
canal and is filled with gas or air.

8. • 5. Lateral line sense organs.
• Fishes have lateral line systems extending all over
the body.
• It contains neuromast organs which act as
rheoreceptors (i.e., detect pressure changes in
surrounding water).

9. • 6. Skin.
• Skin of fishes is rich in mucous glands and is
protected with scales.

10. B. Secondary Aquatic
Adaptations

11. • 1. Stream-lined body.
• The body shape is stream-lined like primarily
adapted forms
• Neck constriction disappears and tail enlarges,
e.g., Ichthyosauria (extinct fish-lizards),
Cetacea (whales, dolphins, and porpoises),
Sirenia (manatees and dugongs).
• Frog also contains stream-lined body.

12. 2. Enlargement of size.
• Aquatic vertebrates tend to be larger in size because
in these creatures energy, which in terrestrial form is
exhausted in gravitational forces, is turned into
growth.
•For example, largest sulphur-bottom whale is several
times bigger than the largest elephant.
•Other example include giant sharks and squids.

13. • 3. Submergence.
• All secondary aquatic animals need to develop
capacity of submergence since swimming below
water surface demands such an adaptation.
• For example, in whales the ribs are strongly
arched, the lungs are massive, the external nostrils
communicate with the median "blow hole" which
is closable.

14. • 4. Shortening of neck.
• There occurs reduction of length and mobility of
neck.
• In whales cervical vertebrae (which are seven in
number like other mammals) are fused to form a
solid and compressed mass of bone.

15. • 5. Disappearance of excrescences.
• The external ears (pinnae) which hinder water
locomotion tend to disappear
• Since they collect sound waves in air medium and
are useless in aquatic forms.
• Thus, ears are reduced in amphibious mammals
and are lost in whales, true seals and walruses.
• The nostrils (nares) move towards the apex of
head as in whales
• Likewise, eyes become water-adapted by shifting
higher on the face as in hippopotamus.

16. • 6. Occurrence of locomotory paddles (fins).
• There occur fleshy and finlike expansions of the
body wall in whales and ichthyosaurs which help
in propulsion.
• These fins may be dorsal or caudal. Dorsal fin is
present in killer whale, while absent in
Delphinopterus and Balaena.
• Caudal fin (also called caudal or tail fluke) of
marine mammals in horizontal (vertical in
reptiles)
• bone divides the tail into two equal parts rather
than running into one lobe.
• In turtles oar propulsion occurs by fin-like limbs

17. • 7. Disappearance of hairs, skin glands
• In whales and sirenians, the skin becomes naked due
to loss of hairs.
• The hair loss is compensated by the formation of a
fatty layer below the skin (blubber) for the retention
of the bodily heat.
• The blubber also has a hydrostatic advantage (e.g., it
helps in
• floatation or to keep positions in the water and act
in combination with the buoyancy of the aquatic
• Sweat or oil glands disappear as they have nothing
to do with the aquatic mode of life.
• Muscles and nerves also atropy from the integument
due to its thickening and immobility.

18. • 8. Mouth armament.
• Since jaws are not used for mastication in whales
they lost the power of movement.
• Teeth become simplified (homodont in dolphins)
and greater in number.
• In sperm whale, teeth are present only on one
jaw or entirely absent from both the jaws (e.g.,
baleen whale)

19. • 9. Skull modification.
• In certain aquatic mammals (e.g., Dolphins,
porpoises) the cranium is shortened and front part
of the skull becomes elongated to acquire the shape
of a rostrum.
• In the skull of the cetacea, the zygomatic arch is
reduced to a vestige.

20. • 10. Simplification of vertebrae.
• In secondarily aquatic forms (vertebrates) the vertebrae tend
to be simple.
• In Ichthyosaurs, vertebrae are simple with biconcave centra
like the fishes.
• Various secondary articulations or zygapophysis become
reduced, as body weight is supported by water.
• The chest too become cylindrical.
• The rib articulations are modified and are central, i.e., they
are articulated to the centrum and are not articulated to the
transverse processes.
• Sacrum in cetaceans and sirenians is more or less reduced,
since it does not withstand and transmit
• the supporting impact of the hindlimbs, as does in terrestrial
forms.

21. • 11. Lightness of bones.
• The bones in aquatic forms are light and
spongy.
• In whales, their interstices are filled with oil.

22. VOLANT ADAPTATIONS
• The Volant adaptations are concerned with flight.
• The flight is a form of locomotion in the air
• Body has to be firstly prevented from falling down
• Secondly moved forwards, the
• Volant adaptations must include modifications in
animals body for reducing weight of the body
• For the formation of organs capable of executing
flight.

23. 1. Passive or gliding type flight
• This type of movement involves no propulsion
other than the
• initial force of jumping.
• Gliding is characterised by leaping or jumping from
a high point and held up by some sustaining organs,
then to glide to lower level.
• Thus, there is no locomotive force

24. Development of patagia.
• The sustaining surface ("wing") for the gliding is a fold
or series of folds of skin, called patagium.
• The patagium lies between forelimbs and hind limbs
and can be folded like a fan against the body when is
not in use.
• Ptychozoon is gliding lizard which is commonly known
as "the flying or fringed gecko" and in which lateral
expansion of skin (patagium) extends along the side of
neck, body, tail and limbs and between toes.
• Flying snakes (e.g., Chryso pelea) leap by the concave
ventral side of body.
• The extinct reptiles pterodactyls of Mesozoic era were
Volant creatures akin to birds, containing true flight
patagia.

25. (ii) Enlargement and high insertion of pectoral fins
• In flying fishes (Exocoetus) are trim-built creatures
with large parachute-like pectoral fins which are
highly inserted on the body.
• The pelvic fins are much smaller in size.
• The lower lobe of tail is also invariably longer,
helping in leaping.

26. (iii) Webbing of feet
• In flying frog (Rhacophorus paradailis the feet are
webbed
• which sustain the prolonged leaps.
• Flying frog's digits terminate in adhesive pads which
help in adhesion to trees.

27. 2. Active or true flight.
• It is the aerial flight caused by the action of wings.
True flight is found in insects, pterodactyls, birds
and bats.
• In all of them the nature of development and
structure of wings are quite different and their
analogy suggest that the flight has evolved
independently in different groups.
• In true flights the power is implied and movement
in air is sustained.

28. Varieties of Wings
1. Insect wings.
• The flying insects develop wings at their last moult.
• The mode of origin of the wing of the insects is different
• The wings are made up of cuticle and are strengthened by
thickenings, called veins.
• Insect flight is affected by flapping movements of wings.
• Typically, there are two pairs of wings developed on
dorsolateral sides of the meso-and meta-thoracic segments.
• The wing muscles are highly striated and are rich in
mitochondria.

29. 2. Bat wing.
• In a bat wing, humerus bone is well developed,
radius is long and curved and ulna is vestigial.
• The pollex (thumb) is free and clawed for crawling
and climbing.

30. 3. Pterodactyl wing.
• In pterodactyl's wings, the radius and ulna bones are
nearly equal.
• The next segment consists of a heavy fourth metacarpal
bearing great wing finger and three small metacarpals
supporting the first, second and third clawed digits.
There Is also present a pteroid bone which is directed
towards the shoulder and supposed to support the
anterior margin of a pre patagium which lies in front of
arm from the wrist to the neck.
• The single wing finger (i.e., fourth) is huge and forms
the entire anterior support of the patagium beyond the
wrist.

31. 4. Bird wing.
• In birds forelimbs are modified into flight structures,
the wings.
• The wings of birds are more specialized of all
modern wings.
• In a wing of bird, digits are reduced to three and
these are fused together to help in flight.
• The metacarpals are three which are unequally
developed and co-ossified.
• The digits are represented by one or two phalanges

32. Volant adaptations of birds.
• Bird flight is characterized by the flapping of the
wings. In flying, the bird lifts its body and drives
forward by beating its wings in a characteristic way.
• An object moved swiftly in the air is affected by two
forces :
• 1. upward pushing (lifting)
• 2. downward pull (drag)
• Birds wings are slightly concave, so are able to
produce the air-current for producing the lifting
force.
• Birds have the following adaptations for true flight

33. Birds adaptations for true flight
1. Body contour.
• The streamlined body is spindle-shaped or boat
shaped, encountering least aerial resistance and
can easily be passed through the air.
• Thus, the beak is pointed; head is compact; neck is
long and mobile and wings are attached high upon
the thorax.

34. 2. Development of feathers.
• The entire body of birds is invested with a close
covering of feathers, constituting the plumage. The
feathers form the exoskeleton of birds.
• These nature's "master pieces“ are light, elastic,
waterproof and most important in flight.
• Bird’s feathers are classified into quill feathers,
contour feathers, down feathers and filoplumes.
• Quills are flight feathers.
• Flight feathers of wings are called remiges and
those of tail are called rectrices.

35. 3. Presence of wings.
• In birds the fore-limbs are modified into wings
helping in flying.
• The hindlimbs or legs are large and variously
adapted for walking, running, scratching, perching,
food-capturing, swimming.

36. 4. Pneumatization of bones.
• The bones of birds are hollow and air filled. They
also contain many air cavities.
• These add buoyancy during flight.

37. 5. Occurrence of flight muscles and keeled sternum.
• In birds, specific flight muscles are developed which
connect the wings with limb bones.
• Each wing is depressed or lowered by an enormous
muscle called pectoralis major.
• It is elavated or raised by pectoralis minor (the
tendon of which is inserted on the head of
humerus).
• The sternum or breast bone is well developed and
bears a median keel or carina for the attachment of
pectoralis muscles.

38. 6. Development of air sacs.
• They act as air reservoir during respiration and
serve as balloons to provide lightness and buoyancy
to the body.
• Air sacs also help in internal perspiration, thus,
helping in the regulation of body temperature.

39. 7. Brain and sense organ’s specificity.
• Cerebrum is well developed (for controlling
manoeuvrability) and optic lobes become enlarged
(for controlling the great development of sight) and
olfactory lobes are reduced (i.e., power of smell is
reduced).
• Bird’s eyes are large and bear characteristic
sclerotic plates to resist variable air pressure.
• Eyes also contain pectens) which are comb-like,
vascular and pigmented structures) to regulate fluid
pressure within the eye (i.e.,accomodation).

40. 8. Beak.
• The conversion of forelimbs into wings is
compensated by the presence of a bill or beak.
• The beak is horny and lacks teeth.

41. 9. Mobile neck.
• The neck of birds is very long and flexible

42. 10. Single ovary.
• Presence of a single functional ovary of the left side
in the female bird also leads to reduction of weight
which is very essential for flight.

43. 11. Absence of urinary bladder.
• Birds do not have a urinary bladder which is present
to store the urine temporarily in other animals.
• Further, birds excrete a semisolid excreta which
chiefly contains the insoluble uric acid and urates
• These features help in reducing the weight of body

44. DESERT ADAPTATIONS
Desert animals or xerocoles have adaptations for
following three sorts :
1. Moisture getting;
2. Moisture conservation
3. Self- defense against physical and organic
environment.

45. 1. Moisture getting
• Use Deep ground water
• Use rain water from the superficial layers
• Absorption of dew water
• Xerophytes plants have varied adaptations.
• The date palm has long deep exploring and
horizontally spreading roots.
• The sand lizard or Moloch has hygroscopic skin to
absorb water like

46. 2. Moisture conservation.
(i) Camel exhibits many adaptations for water conservation
(ii) To avoid water loss through skin, the horned toad has hard
and rough skin.
(iii) Uromastix (desert lizard) store water in large intestine.
(iv) Desert mammals has thick skin , reduced number of sweat
glands in the skin
(v) Desert insects are wax proof.
(vi) To conserve water, desert animals remain in burrows during
the day time and come outside during night when the
percentage of moisture in their burrow and outside is equal.
(vii) Certain animals plug the mouth of their burrows during day
time.

47. 3. Self defense against scorching sun.
(i) In burrow-digging species of reptiles, the nostrils are
directed upward instead of forward. In most snakes
nostrils are either reduced to pin holes or protected by
complicated valves.
(ii) The eyes of Typhlops are overhung by the sheath. In
ostrich and camel, the eyes are protected by reflecting
heat of the sand by possessing the long neck.
(iii) In lizard Mabuya, the lower lip becomes enlarged with
a transparent window in it.
(iv) The ear opening of desert animals is either small or
protected by fringes or scales or they may be abolished.
(v) Possession of venom is another desert adaptation
(vi) Gazelle (antelope) resembles the general coloring of
landscape