Locomotion in Vertebrates [with MCQs & FAQs]

Swimming in Fishes

Swimming in water provides very different problems from strolling on land like a man or flying in the air like birds. The body of many fishes is streamlined, being tapered at both ends.

This indicates that water flows readily over the body surface and friction is decreased to a minimum.

Apart from the fins, no other structures project from the body of the fish and it appears that the faster the fish, the more perfect the streamlined.

The dermal denticles of cartilaginous fish and the scales of bony fish are kept damp by slimy exudation from mucous or oil glands and this also significantly minimizes friction between fish and water.

Other adaptations possessed by fish for moving efficiently through the water are the fins.

The dorsal and ventral, unpaired fins assist in stabilizing the fish, the paired pectoral and pelvic fins are utilized for guiding and stabilizing the animals, and the caudal or tail in, in coordination with paired fins provide forward movement of fish through water.

Buoyancy in the water is preserved by a specialized structure in bony fish called a swim bladder.


Locomotion in Amphibian

The general build of the body is essentially fish-like in amphibians. Such forms have two methods of mobility. They twitch along their tummy on the ground with the help of segmentally arranged muscles as they “swim on land”, with legs barely touching the ground when moving deliberately.


On the other hand, a few raise up their body on the legs which then propel them along as movable levers. In the anurans, the whole skeleton and muscular system have become specialized for the strange swimming and jumping methods of locomotion; using extensor thrusts of both types of limbs, acting together. Frogs and toads also walk and hop on land due to their strong hind limbs.

Mobility in Reptiles

The lifestyle of reptiles exposes striking adaptations for mobility. They move better than amphibians due to the advancement of the skeleton. The reptiles utilize the approach of walking and running. The general type of the reptilian skeleton is based upon one acquired from ancient amphibians.


The skeleton is extremely ossified to offer greater assistance. Reptiles have cervical vertebrae. The first two cervical vertebrae (atlas and axis) offer higher flexibility of movement for the head. The axis is modified for rotational motion. The ribs of reptiles may be highly modified.

The ribs of snakes have muscular connections to large belly scales to assist mobility. Lots of prehistoric reptiles were bipedal meaning that they walked on hind limbs. They had a narrow pelvis and a heavy extended tail for balance. Bipedal mobility freed the front appendages, which became adjusted for prey capture or light in some animals.

Locomotion in Birds

The skeleton of a bird is modified for flight. The most obvious adaptations are the bones with big air spaces which make them lighter. The forelimbs progressed into wings with really strong pectoral muscles that pull the wings up and down. The breast bone is modified to form a keel. The keel is needed for the attachment of muscles. The body is covered with feathers which provide the wing a big surface area to keep the birds in the air.

They also keep their bodies warm, so that they can produce adequate energy to fly. The body is streamlined to cut clearly through the air. The plumes lie efficiently against its body so that the air can quickly flow over them. A bird can fly either passively by moving or actively by flapping its wings.

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Passive flight:

When birds slide, the wings function as aerofoils. An aerofoil is any smooth surface area that moves through the air at an angle, to the airstream. The air flows over the wing in such a way that the bird is offered lift; the quantity of lift depends on the angle at which the wing is held relative to the airstream.

Active flight:

When little or no support can be obtained from upward air currents, the same effect can be achieved by flapping the wings. As the birds move through the air, the air flows more quickly over the curved upper surface than over the lower surface. This decreases the atmospheric pressure on the top of the wing, compared with atmospheric pressure below the wing. There is, for that reason, a net upward pressure on the wing which provides lift to the bird.

Mobility in Mammals

The most efficient method of supporting the body is seen in mammals. The limbs of the mammals have actually gone through further modifications to produce the following modes of mobility.


  1. Plantigrade:

In this mode of locomotion, the mammals walk on their soles with palms, wrists, and digits all resting basically on the ground, such as monkeys, apes, men, bears, etc.

  1. Digitigrade:

Some mammals tend to walk on their digits just. They run faster than plantigrade animals. In these mammals, the first digit is generally reduced or entirely lost as in rabbits, rodents, etc.

  1. Unguligrade:

These mammals walk on the tips of toes modified into hoofs such as deer, and goat. It is the swiftest kind of locomotion.


  1. What is the primary purpose of the streamlined body in fishes for swimming?
    • A. To increase friction
    • B. To decrease water flow
    • C. To minimize friction
    • D. To hinder forward movement

    Answer: C

  2. How do fish maintain buoyancy in water?
    • A. By using slimy exudation
    • B. Through specialized structures called swim bladder
    • C. By having fins on both ends
    • D. By reducing friction with oil glands

    Answer: B

  3. In amphibians, what are the two methods of mobility mentioned?
    • A. Flying and walking
    • B. Swimming and jumping
    • C. Slithering and crawling
    • D. Running and climbing

    Answer: B

  4. What skeletal adaptation do reptiles have for better movement compared to amphibians?
    • A. Highly ossified skeleton
    • B. Increased number of limbs
    • C. Decreased flexibility
    • D. Lack of cervical vertebrae

    Answer: A

  5. Why is the keel important in the skeleton of birds?
    • A. To increase weight
    • B. For attachment of muscles
    • C. To reduce air resistance
    • D. To hinder flight

    Answer: B

  6. What provides lift to birds during passive flight?
    • A. Flapping wings
    • B. Aerofoils
    • C. Feather structure
    • D. Streamlined body

    Answer: B

  7. When do birds achieve lift through active flight?
    • A. When sliding
    • B. When gliding
    • C. When flapping wings
    • D. When standing still

    Answer: C

  8. How are the forelimbs of birds adapted for flight?
    • A. Large air spaces in bones
    • B. Short and heavy
    • C. Lack of feathers
    • D. Small muscles

    Answer: A

  9. Which mode of locomotion involves walking on the soles with palm, wrist, and digits all resting on the ground?
    • A. Digitigrade
    • B. Unguligrade
    • C. Plantigrade
    • D. Bipedal

    Answer: C

  10. Which mammals walk on their digits only?
    • A. Primates
    • B. Ungulates
    • C. Rodents
    • D. Carnivores

    Answer: A

  11. What is the swiftest form of locomotion among mammals?
    • A. Plantigrade
    • B. Unguligrade
    • C. Digitigrade
    • D. Bipedal

    Answer: B

  12. What is the purpose of the swim bladder in fish?
    • A. To decrease buoyancy
    • B. To increase friction
    • C. To maintain buoyancy
    • D. To assist in jumping

    Answer: C

  13. Which part of the bird’s skeleton is modified to form a keel?
    • A. Pelvis
    • B. Breast bone
    • C. Wings
    • D. Skull

    Answer: B

  14. What type of motion do reptiles use for better mobility?
    • A. Sliding
    • B. Walking and running
    • C. Jumping
    • D. Flying

    Answer: B

  15. What is the primary purpose of the dermal denticles in cartilaginous fish?
    • A. To increase friction
    • B. To decrease buoyancy
    • C. To minimize friction
    • D. To hinder movement

    Answer: C

  16. Which type of flight involves wings functioning as aerofoils?
    • A. Active flight
    • B. Passive flight
    • C. Gliding
    • D. Hovering

    Answer: B

  17. What allows the faster flow of air over the curved upper surface of a bird’s wing during active flight?
    • A. Flapping wings
    • B. Aerofoils
    • C. Feather structure
    • D. Streamlined body

    Answer: A

  18. What is the primary purpose of the large air spaces in bird bones?
    • A. To increase weight
    • B. To decrease air resistance
    • C. To provide lift
    • D. To hinder flight

    Answer: B

  19. In which animals do the paired pectoral and pelvic fins play a role in guiding and stabilizing?
    • A. Amphibians
    • B. Fishes
    • C. Reptiles
    • D. Birds

    Answer: B

  20. What is the main method of locomotion in mammals with a plantigrade stance?
    • A. Flying
    • B. Jumping
    • C. Walking
    • D. Slithering

    Answer: C

  21. What skeletal adaptation allows reptiles to have higher flexibility of head movement?
    • A. Highly ossified skeleton
    • B. Lack of cervical vertebrae
    • C. Presence of swim bladder
    • D. Bipedal stance

    Answer: B

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FAQs about Locomotion in Vertebrates

  1. Q: What is the significance of the streamlined body in fishes for swimming?
    • A: The streamlined body reduces friction as water flows over the surface, making swimming more efficient for fishes.
  2. Q: How do fish maintain buoyancy in water?
    • A: Fish maintain buoyancy through a specialized structure called a swim bladder.
  3. Q: What are the two methods of mobility in amphibians?
    • A: Amphibians either twitch along their tummy on the ground or raise their body on legs for movement.
  4. Q: How do reptiles differ in mobility from amphibians?
    • A: Reptiles move better than amphibians due to skeletal advancements, utilizing walking and running as their primary modes of mobility.
  5. Q: What skeletal adaptations do reptiles have for enhanced mobility?
    • A: Reptiles have an ossified skeleton with cervical vertebrae, allowing greater flexibility, and some may have modified ribs for better mobility.
  6. Q: What is the keel in the skeleton of birds and why is it important?
    • A: The keel is a modified breastbone, crucial for the attachment of strong pectoral muscles needed for flight in birds.
  7. Q: How do birds achieve lift during passive flight?
    • A: In passive flight, wings function as aerofoils, creating lift as air flows over them at an angle.
  8. Q: What is the purpose of large air spaces in bird bones?
    • A: The large air spaces make bird bones lighter, aiding in flight by reducing overall weight.
  9. Q: How do mammals with a digitigrade stance differ in locomotion from plantigrade mammals?
    • A: Digitigrade mammals walk on their digits only, running faster than plantigrade mammals that walk with palm, wrist, and digits resting on the ground.
  10. Q: What is the primary purpose of feathers in birds for flight?
    • A: Feathers provide a large surface area for wings, aiding in flight and helping birds cut through the air efficiently.
  11. Q: How do mammals with an unguligrade stance move?
    • A: Unguligrade mammals walk on the tips of toes modified into hooves, making it the swiftest form of locomotion.
  12. Q: What is the role of dorsal and ventral fins in fishes?
    • A: Dorsal and ventral fins in fishes assist in stabilizing the fish, while paired pectoral and pelvic fins are used for guiding and stabilizing.
  13. Q: How do birds achieve lift during active flight?
    • A: Birds achieve lift in active flight by flapping their wings, creating a net upward pressure due to the faster flow of air over the curved upper wing surface.
  14. Q: What is the primary purpose of the swim bladder in bony fish?
    • A: The swim bladder in bony fish helps maintain buoyancy in water by regulating the fish’s internal pressure.
  15. Q: Why do some reptiles exhibit bipedal mobility?
    • A: Bipedal mobility in some reptiles frees the front appendages for activities like prey capture or light, with adaptations in the pelvis and tail for balance.
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Wrap up

The tutorial on locomotion in vertebrates covers the diverse methods of movement employed by different classes of animals, including fishes, amphibians, reptiles, birds, and mammals. Each section delves into the unique adaptations that enable these vertebrates to navigate through their respective environments.

  1. Swimming in Fishes:
    • Fishes exhibit a streamlined body to reduce friction and fins for efficient water movement.
    • Dermal denticles and scales, kept damp by mucous or oil glands, further minimize friction.
    • Fins, including dorsal, ventral, pectoral, pelvic, and caudal, play distinct roles in stabilizing and guiding fishes.
  2. Locomotion in Amphibians:
    • Amphibians demonstrate two mobility methods: “swimming on land” using tummy muscles and leg-based movement.
    • Anurans (frogs and toads) have specialized skeletal and muscular systems for swimming and jumping.
  3. Mobility in Reptiles:
    • Reptiles, with an advanced and ossified skeleton, employ walking and running for mobility.
    • Cervical vertebrae, modified ribs, and adaptations for bipedalism are notable features in reptilian locomotion.
  4. Locomotion in Birds:
    • Birds have a modified skeleton adapted for flight, with large air spaces in bones for reduced weight.
    • Wings, covered in feathers, are pivotal for passive and active flight, involving aerofoils and flapping.
  5. Mobility in Mammals:
    • Mammals exhibit diverse modes of mobility, including plantigrade (walking on soles), digitigrade (walking on digits), and unguligrade (walking on toes/hooves).
    • Limb modifications in mammals cater to specific locomotor strategies.

The tutorial provides a comprehensive understanding of how vertebrates have evolved distinct mechanisms for movement, showcasing the remarkable adaptations that allow them to thrive in their respective habitats.