Animal Design and Locomotion

Introduction

  • Speaker: Dr. Sarah Channon
    • Position: Associate Professor in Veterinary Anatomy
    • Roles: Co-Strand Leader for Locomotor Strand, Associate Dean for Undergraduate Teaching, Learning, and Assessment
    • Contact: schannon@rvc.ac.uk

Learning Objectives

  • Objective 1: Describe how animals are adapted for posture and movement.
  • Objective 2: Describe the roles of the thoracic and pelvic limb and the spine in locomotion.
  • Objective 3: Discuss anatomical adaptations of the limbs specific to different locomotor needs and behaviors.

Locomotion from an Evolutionary Perspective

  • Selection Pressures:
    • Resources: Habitat, food, mates
    • Environment: Temperature, weather, access (geographical factors)
    • Biological Factors: Predators, pathogens (diseases)

Goals of the Locomotor System

  • The locomotor system must achieve the following:
    • Support Body Mass: Maintain structural integrity under the weight of the animal.
    • Move Centre of Mass (COM): Coordinate movements to adjust the body’s center of mass.
    • Move Limbs: Enable effective limb motion that is efficient and purposeful.
  • Energy Consumption: Locomotion must use energy efficiently while overcoming gravity to move the COM and limbs.

Selection Pressures and Locomotion

  • Animals must:
    • Move across different substrates.
    • Change direction as needed.
    • Adapt to various speeds while minimizing energy expenditure.

Principles of Locomotor Design (1)

Quadrupeds

  • Differences in Quadrupedal Locomotion:
    • Carnivores vs. Herbivores: Design adaptations based on lifestyle and dietary needs.

Quadrupedal Carnivores

  • Adaptations for Speed:
    • Hunting agility requiring quick movements to capture prey.
  • Key Features Supporting Speed and Agility:
    • Muscle Bulk: Greater muscle mass leads to more power.
    • Overall Body Mass: Influences speed and stability.
    • Skeletal Arrangement: Spine and leverage for muscular advantage.
    • Foot Structure: Grippy adaptations for traction.

Muscle Role in Locomotion

  • Force Production: Muscles generate forces within limbs, enabling joint support and movement.
  • Power Generation: Rapidly producing large forces contributes to agility.

Factors Contributing to Locomotor Efficiency

Body Mass

  • Force Equation:
    • F=maF = ma (Force equals mass times acceleration.)
  • Body Mass Limitations: Affects limb structure and locomotion functionality.
  • Ground Reaction Forces (GRF): Essential to understand their role in movement dynamics.

Skeletal Arrangement

  • Influences Muscle Action:
    • Different vertebrae contribute to spinal mobility and flexibility, enabling increased stride length and speed.

Grip and Traction Importance

  • Adaptations for Increased Grip:
    • Pads, multiple digits, and accessory structures like claws enhance grip, improving agility and maneuverability.

Quadrupedal Herbivores

Principles of Locomotor Design (1)

  • Adaptations for Endurance:
    • Lower energy costs for long migrations and escaping predation.

Features Supporting Efficiency and Endurance:

  • Elastic Tissues: Tendons crucial for storing and releasing energy.
  • Skeletal Arrangement: Optimizing limb length and weight for effective locomotion.
  • Pectoral Girdle Specialization: Enhancements for stability and movement.

Skeletal Arrangement

Lengthening and Lightening the Distal Limb

  • Different locomotion types:
    • Plantigrade: Walking on the soles of the feet (e.g., humans).
    • Digitigrade: Walking on toes (e.g., dogs).
    • Unguligrade: Walking on hooves (e.g., horses).
    • Term ‘ungulate’ denotes hoof-bearing animals.

Pectoral Girdle Anatomy

  • Anatomy includes scapula, clavicle, and associated muscles (trapezius, rhomboideus, serratus, and pectoralis).
    • Role in supporting the forelimb during movement.

Trade-offs in Limb Design

  • Manipulation vs. Locomotion:
    • Manipulative ability may be compromised due to the evolution of limb structure (loss of digits, increased tendon function).
  • Tool Use in Bipeds:
    • Bipedalism encourages manipulation abilities (e.g., carrying tools).

Comparative Limb Functions

  • Differentiated Limb Functions:
    • Forelimb grasping forces typically approximately 30% higher than hindlimbs, impacting overall biomechanics.

Summary of Key Ideas

  • Locomotion as a Fundamental Behavior:
    • Most significant factor influencing an animal’s morphology and physiology.
  • Influencing Factors:
    • Natural selection, environmental pressures, competition, anatomical design principles.
  • Key Principles in Locomotion:
    • Muscle function, body mass limitations, skeletal adaptations, grip mechanisms, and manipulation requirements.
    • Compare quadrupedal vs. bipedal locomotion, focusing on speed versus endurance.

One Health Relevance

  • Animal Health and Welfare:
    • Design influenced by breeding practices and human-imposed selection pressures.
  • Public Health Concerns:
    • Human performance bound by anatomical and biomechanical limits.
  • Ecosystem Health and Sustainability:
    • Selection pressures shape interspecies relationships and overall ecosystem dynamics.

Further Reading

  • Key Text: Functional Anatomy of the Vertebrates, Chapter 11 (pg 360-380).
  • Additional Resources:
    • Dick TJM, Clemente CJ (2017). "Where Have All the Giants Gone?" PLOS Biology 15(1).
    • Biewener, A. A. (1990). "Biomechanics of mammalian terrestrial locomotion." Science 250:1097.
    • Dickinson et al. (2000). "How animals move: an integrative view." Science 288:100-106.

Questions?