Mammalian Evolution and Locomotion

Flashcards reviewing key concepts from a lecture on mammalian evolution, locomotion, and energetics.

What is a key characteristic of Synapsida?

One temporal fenestral.

What are two key characteristics of ALL mammals?

Mammary glands to nourish young and endothermy.

What happens to 3 cranial bones during mammalian evolution?

They migrate to the inner ear.

What are the defining traits for all mammals?

Mammary glands, endothermy, hair, heterodont dentition, and single bone lower jaws.

What are the functions of teeth?

Canines tare, molars/premolars grind.

What adaptations do mammals possess that allows them to chew and breathe at the same time?

Secondary palate; separates mouth from nasal cavity

What is hair used for among mammals?

Social interaction and insulation.

What is a major thermal adaptation seen in humans?

Sweat glands all over the body.

What are three functions of animal movement?

Acquiring food, avoiding predation, and social interaction.

What does mammalian stance allow for?

locomotion and breathing can be done at same time

What is a key feature of mammalian posture related to energy expenditure?

Lower ground reaction forces (GRFs) compared to reptiles which saves energy.

What skeletal feature is conserved across nearly all mammals?

Seven cervical vertebrae.

What characteristics do cursorial animals have to help compensate for gravity?

Adaptations to support weight, resist ground forces, and forces by the muscles themselves.

What are the three foot postures for terrestrial locomotion?

Plantigrade, digitigrade, and unguligrade.

What is achieved by increased limb length in mammals?

Speed and higher stride lengths and frequencies.

What does walking as a form of locomotion defined by?

No aerial phase; at least one leg in contact with the ground.

What happens as an animal's size increases, regarding locomotion?

They take better advantage of locomotion strategies like elastic energy (free energy through tendon-usage)

What is an adaptation some mammals, such as kangaroos, exhibit?

Decoupling energy use from running speed by taking advantage of elastic energy within the Achilles tendon.

What are some typical adaptations of fossorial (digging) mammals?

Large claws, lack pinnae (ear flaps), small eyes, and/or short, broad forelimbs splayed to the side.

What are some adaptations for climbing mammals?

Modified appendages to allow for balance, claws, prehensility (hands, feet, tail), or suspensory adaptations (long curved digits).

What do flying mammals utilize?

Special membranes and modifications to the arm to maintain different modes of aerial locomotion.

What features do swimming mammals have?

Thick fur or subcutaneous fat (blubber); webbed feet/flippers; tail may be flattened.

Give some adaptations exhibited by fully aquatic mammals.

Reduction or loss of the pelvic girdle, and vertical undulations

What happens to muscle action as running speed increases?

The metabolic cost increases linearly.

What is the relationship between body size and energy usage?

Mass-specific use of energy decreases as a function of weight; larger animals require less energy per gram of body mass compared to smaller animals.

What four things is food used for, regarding energy?

Maintenance of homeostasis, reproduction, gas exchange, and locomotion.

Why must shrews forage constantly?

They have exorbitant energy demands; they need to consume 200-300% of their body weight each day to survive.

What are the four main stages of food processing?

Ingestion, digestion, absorption, and elimination.

What must all mammals fight against?

Effects of drag

How do Phocids (true seals) swim?

They swim with back muscles/flippers; very energy efficient, longer divers, and deeper

How do Otariids (sea lions and fur seals) swim?

They primarily use their front flippers; more active, shallower divers and shorter

How do leopard seals swim?

Combination of the way Phocids & Otariids swim; front and back flippers

What are characteristics of fossorial mammals and what does it mean to be fossorial?

“diggers” Equipped to burrow, move soil substrate, using forelimbs and sometimes incisors, large claws, short broad forelimbs splayed to side, more vibrissae than terrestrial mammals

What are characteristics of Arboreal (tree climbers) and Scansorial (trees and ground climbers)?

Claws, prehensility— hands, tail and feet (nails not claws), Suspensory (hanging)— long, curved digits, fusion of cervical vertebrae

What is and are common characteristics of brachiation?

Unique primate form of locomotion using arms to move, shorter spine, flexible shoulder/wrist joint, pendulum motion

What are characteristics of Volant (aerial) mammals?

Special membranes, modified arms to maintain different modes of aerial locomotion

Describe flying in bats versus gliding in other mammals

Flying: bat wings malleable and energy spent to keep membrane taut and propel body in air

Gliding: characterized by patagium (membrane), very little metabolic energy required, velocity from gravity