Mammalian Biology - Sensory Systems, Vision, Locomotion, and Teeth

Flashcards covering key vocabulary and concepts related to sensitivity, vision, teeth, locomotion, and breathing in mammals.

Auditory Sensitivity

Auditory receptors can detect small vibrational displacements; the basilar membrane vibrates between 10-10 and 10-11 cm, which is less than the diameter of a hydrogen atom (10-8 cm).

Hair Cell Length and Frequency

Progressive increase in length from base to tip; Shortest hairs respond to high frequencies (~20 kHz), longer hairs to lower frequencies (~100 Hz).

Owl Hearing

Differential hearing ability; can distinguish 0.00003 s, equivalent to 1 cm in distance; Asymmetric ear placement.

Infrasound

Ultra-low frequency sound detection in birds; used for communication by elephants, whales and crocodiles.

Echolocation/Sonar

Transmitter-receiver sensory system; same principles in air and water, but less attenuation in water (4x faster).

Rods

Mainly in peripheral regions of the retina and absent from the fovea; human fovea has ~150,000 cones per mm2.

Opsin

Polypeptide chains differ in sequence, hence sensitivity and color perception; trans-membrane with internal Retinal A vitamin.

Vertebrate Vision

Transition from 11-cis to all-trans initiates receptor potential; Bleaching Regeneration via enzymatic isomerization (5-30 minute half-life).

Color Vision

Most Teleost fish, reptiles, and birds have 4 different opsins genes and are Tetrachromic colour (photopic) vision. Mammalian colour vision is usually dichromatic (cone genes S and L).

Trichromatic Vision in Primates

Duplicated L opsin gene to give L, M, S, allowing up to 2 million colors to be distinguished.

Color Vision and Pigments

Single photopigment cannot differentiate between intensity and wavelength of light; requires 2 or >2 photopigments.

Nocturnal Mammal Vision Adaptations

Larger eyes; S = ( / 4)2 (D/f)2 Dr 2 (1-e-kl) D=eye diameter, f=focal length, Dr=photoreceptor diameter, l=length/depth of photoreceptive layer; more rods or absent cones; many-to-one connections.

Accommodation

Ability to change focal length of lens.

Focusing in Water (Vision)

Aquatic organisms need more spherical lens; amphibious animals have difficulties focusing in both air and water.

Visual Field vs. Precision

Laterally placed eyes give all-round vision; Forward facing eyes give binocular vision

Diphyodonty

Norm for mammals; some have ever-growing teeth (rodents/lagomorphs, elephants, kangaroos).

Differentiation of Teeth

Incisors (cutting), canines (piercing/holding), premolars/molars (slicing, crushing/grinding).

Tribosphenic Molars

Tribo (grinding) + Sphen (shearing) multifunctional; defining apomorphy of placentals/marsupials.

Brachydont

Low crowned teeth

Hypsodont

High Crowned teeth

Tusks

Incisors (elephants) or canines (walrus, narwhal).

Foot Postures

Plantigrade, Digitigrade, Unguligrade.

Types of Locomotion

Generalized/ambulatory, Cursorial, Scansorial/arboreal, Bipedal, Fossorial, Graviportal, Saltatory/richochetal, Natatorial/aquatic, Volant, Glissant.

Ambulatory Mammals

Mobile joints, ability to rotate hand, five digits, plantigrade/semi-digitigrade posture, equal limb segment lengths.

Cursorial Mammals

Hooves often present, restricted mobility, long thin scapula, loss of clavicle, tendons/ligaments act as springs.

Cursorial Mammals & Axial Skeleton

Shift from lateral to vertical flexion of vertebral column, limbs swung in same plane, loss of ribs from posterior trunk.

Cursorial Specializations

Elongation of intermediate and distal limb elements, extreme digitigrade/unguligrade posture, muscle mass close to body, reduction of digits.

Bipedal Mammals (Humans)

Only habitual non-jumping bipeds; plantigrade stance, vertically oriented pelvis, short/absent tails, short flared pelvis, extremely long femur, down-turned heel, large/elongated pollux.

Saltatory/Ricochetal Mammals

Usually propelled by hind limbs (longer than forelimbs), metatarsals long/tibia-fibula fused, small unspecialized forelimbs, long tail for counterbalance, tridactyl foot.

Saltatory Locomotion Adaptations

Elastic energy storage in tendons of distal limb.

Specialized Lungs for Terrestrial Living

Alveoli increase surface area, more elastic (surfactants), tidal air flow, pump driven by muscular movements (low metabolic cost).

Breathing and Gas Exchange

Bats lose up to 12% of CO2 through wing membranes; functionally coupled with locomotion in fast mammals.