Herpetology; Locomotion (3/30)

First Law: A body at rest will remain at rest, and a body in motion will remain in motion unless acted upon by an external force.
Second Law: Force equals mass times acceleration, $F = m imes a$ .
Third Law: For every action, there is an equal and opposite reaction.

Muscles produce a force that pushes down on the substrate, generating an equal and opposite reaction force from the ground.
The reaction force can be divided into two components:
- Vertical Component: Resists gravity.
- Propulsive Component (F): Moves the animal forward.

First Class Lever:
- A lever where the fulcrum is between the input and output forces.
- Example: The ankle joint.
- In Lever: Moved by an input force (e.g., gastrocnemius muscle).
- Out Lever: Moves output away from the fulcrum.
Third Class Lever:
- Both the in lever and out lever move in the same directional pivot around the fulcrum.
- Example in lizard anatomy: the jaw joint and the muscles attached to it, such as the depressor mandibular and adductor mandibular.

Discusses locomotion in reptiles and amphibians, beginning with terrestrial modes.

Most tetrapod vertebrates, such as salamanders and lizards, exhibit a sprawling posture.
When not moving, body remains flat on the ground; movement begins by propping the body upward to shift weight and maintain balance.
Different patterns of limb movement (e.g., lateral footfall) and how they relate to the center of gravity.

Used by salamanders and swimming lizards, occurring while moving in water, this involves reducing friction by drawing limbs close to the body.

Monitors like the Perentie can run continuously due to specialized breathing mechanisms and physical adaptations enabling endurance.
Capable of reaching speeds over 20 miles/hour.

Pectoral Girdle Adaptation: Sliding joints increase mobility and accelerate stride length.
Dynamic Bipeds: Some lizards, like frilled lizards, move dynamically on two legs rather than standing upright.

Crocodilians display parasagittal limb movements, moving limbs in parallel to the body midline, unlike lizards.
Use a high walk for terrestrial movement; can run quickly for short bursts.

Turtles, having limited vertebral movement, adjust their limbs for propulsion by shifting weight with each step.

In frogs, jumping is an evolved locomotion with modifications in anatomy: elongated metatarsals and phalanges facilitate powerful jumps.
Muscle Mechanics: High-speed studies reveal frogs load muscles with elastic energy for jumping efficiency.

Aquatic reptiles alternative methods of locomotion; snakes and aquatic salamanders utilize lateral movements and axial undulation.
Hydrofoil Mechanism: Explains how aquatic species generate lift and navigate water.
Snakes exhibit both lateral undulation and a unique swimming style due to buoyancy effects in water.

Frogs kick their webbed hind limbs while the forelimbs assist in direction, with varying adaptations present in aquatic versus terrestrial species.

Burrowing reptiles have specialized features (e.g., shovel-shaped skulls) for moving through sand or loose substrates.
Discussion of limbless locomotion in snakes using concertina techniques, aiding movement in tunnels or tight spaces.
Sand swimmers incorporate body movement and specialized scales to navigate shifting sands efficiently.

Overview of diverse locomotion types in reptiles and amphibians, highlighting evolutionary adaptations and biomechanics involved in different environments.