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Questions and Answers
What does biomechanics specifically study?
What does biomechanics specifically study?
Obligate bipedalism is a feature of all mammals.
Obligate bipedalism is a feature of all mammals.
False
Which skeletal adaptation is observed in elephants compared to small animals?
Which skeletal adaptation is observed in elephants compared to small animals?
Thicker, robust bones and straight, column-like posture
The first tetrapods developed a ______ posture, which was ancestral.
The first tetrapods developed a ______ posture, which was ancestral.
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Match the animal with its type of locomotion:
Match the animal with its type of locomotion:
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Which of the following statements about bipedalism is true?
Which of the following statements about bipedalism is true?
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Spinosaurus is known for having hand fossils that support its bipedalism.
Spinosaurus is known for having hand fossils that support its bipedalism.
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What type of locomotion does quadrupedalism refer to?
What type of locomotion does quadrupedalism refer to?
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Study Notes
Biomechanics
- Study of animal movement
- Often referred to as "the mechanics of life"
- Examines how animals navigate and adapt to their environment
Biomechanics of Extinct Animals
- Provides insights into animal forms not seen today.
- Helps understand the physical limitations of extinct animals.
- Studies functional adaptations like terrestrial movement and flight.
- Examples: Quetzalcoatlus (pterosaur), Patagotitan (sauropod)
Skeletal Adaptations to Size
- Small animals do not scale proportionally.
- Small animals have thinner bones and crouched postures.
- Larger animals have thicker, more robust bones and a straighter, column-like posture.
- Examples: Wood mouse, Elephant
Posture
- Sprawling posture was ancestral to tetrapods.
- Erect posture, seen in dinosaurs and mammals, requires special adaptations.
- Open hip socket in dinosaurs supports erect posture.
- Examples: Early tetrapod trackway, Early tetrapod Seymouria
Quadrupedalism
- Movement on all four limbs.
- Ancestral locomotion in most tetrapods, providing stability.
- Movement involves rotation of the chest and hips.
Bipedalism
- Movement on two hind limbs.
- Obligate bipedalism is seen in birds and humans.
- Obligate bipeds typically have erect postures.
- Ancestral to dinosaurs, enabling flight and increased manual dexterity in humans.
- Occasional or partial bipedalism observed in other mammals.
- Examples: Ostriches, dinosaurs like Tyrannosaurus
Bipedalism—Further Innovations
- Enabled new innovations like flight (in birds).
- Increased manual dexterity and tool use in humans.
Bipedalism—Other Forms
- Occasional bipedalism observed in other mammals and reptiles.
- Kangaroos adopt tripodal stance using three limbs.
Postural Enigma
- Spinosaurus (Late Cretaceous theropod).
- Inhabiting Egypt & Morocco
- Unlike other theropods, its wrists can't pronate for hand support
- Fossils of its hands or forearms are missing
Speed
- Scientists measure running speeds from live animals.
- Analyze stride length with statistical analysis.
- Historical biomechanicist, Dr. Robert McNeill Alexander, derived relationships between speed, stride length, and body size in dinosaurs.
Alexander's Dinosaur Speed Calculator
- Predicted running speeds based on stride length and body size.
- Formulas to calculate speed were developed using empirical observations on modern animals, and applied to dinosaur fossils.
Speed—Dinosaurs (How Fast?)
- Small dinosaurs could run fast (>35 km/hr).
- Large dinosaurs like Tyrannosaurus were slower (<10 km/hr).
- Some results yielded high speeds for large dinosaurs.
Adaptations to Speed and Size
- Cursorial animals have longer distal limbs than proximal.
- This increased running efficiency and speed.
- Crural index (tibia-to-femur ratio) is an important factor.
- Graviportal animals have longer proximal limbs for stability and robustness.
- This helps in supporting large body sizes. Different types of foot postures; Plantigrade (entire foot touches ground), Digitigrade (only part of the foot), Unguligrade (only toes or tips of toes touch ground).
Adaptations to Speed and Size—Further Considerations
- Erect digitigrade and unguligrade postures reduce locomotion costs.
- Speed increases with size, but the rate of increase decreases (quadratic scaling).
- This limits speed in larger animals.
Evolution of the Horse
- Shows the evolutionary history and anatomical changes through time, from ancestors of the horse to the modern-day horse
- Detailed representations of fossil horses
Increasing Stride
- Multiple strategies to increase stride and speed without changing limb length or posture.
- Strategies include lateral and sagittal spine movements, and pelvic rotation during movement. These movements aid in more efficient stride and faster speeds.
- The adaptations are inherited, dictating movement.
Conserving Energy
- Pendular movements (gravity) help conserve energy.
- Flexibility (springs) in joints help conserve energy.
- Tendons and ligaments act as natural springs for conserving energy.
- Fusion and digit reduction increase organism support and stability.
Physics and Convergence
- Trends in posture, stance, and locomotion repeat through evolutionary history.
- Repeated forms adapted for similar functions through convergent evolution.
Conclusions
- A general trend exists in evolving toward straighter postures and more robust, graviportal limbs with larger animals.
- Cursorial animals typically have longer distal legs, and are usually digitigrade or unguligrade.
- Speed can be increased in larger animals through stride length enhancements.
- How bodyplans (plans for constructing a body) are inherited dictates evolution.
- Vertebrate animals have adaptations for conserving energy during movement.
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Description
This quiz explores the fascinating field of biomechanics, focusing on animal movement. It examines the adaptations of both extant and extinct species, including skeletal adaptations related to size and posture. Understand how these factors influence the locomotion and behavior of various animals.
