Mammalian Biology Review: Integument, Locomotion, Feeding, Reproduction, and Adaptations

Vocabulary practice flashcards covering mammalian integumentary structures, locomotion specializations, feeding adaptations, reproductive diversity, thermoregulation, and modes of communication.

Epidermis

The outermost region of the integument consisting of several cellular layers, topped by an outer layer of dead, keratinized cells.

Dermis

A highly vascularized layer of connective tissue beneath the epidermis that contains numerous nerves and structures extending into the epidermis.

Hypodermis

The subcutaneous layer of fatty tissue located beneath the dermis that provides insulation and padding.

Sebaceous glands

Epidermally derived glands generally associated with hair follicles that secrete oily products.

Eccrine glands

Epidermally derived glands with coiled ducts producing watery secretions (sweat) not associated with hair; found mainly on hairless pads in non-primates and across most of the body in primates.

Apocrine glands

Epidermally derived glands producing viscous fluids used for chemical signaling; distributed over most of the body in non-primates but restricted to areas like the armpits, nipples, and anogenital region in primates.

Arrector pili muscle

A smooth muscle associated with hair follicles that erects the hair to increase pelage insulation or make the mammal appear larger.

Unguis

The hard, curved, dorsal keratinized plate forming the exterior portion of a mammalian claw, nail, or hoof.

Subunguis

The softer ventral keratinized layer located beneath the unguis in mammalian claws, nails, and hooves.

Saltatorial locomotion

A specialized jumping and ricocheting mode of locomotion characterized by lengthened hindlimbs, fused limb bones (e.g., tibiofibula, cannon bone), long elastic tendons, and a heavy counterbalancing tail.

Chisel-tooth diggers

Fossorial mammals that use massive, procumbent gnawing incisors and powerful jaw and neck musculature to dislodge soil (e.g., Cryptomys, Spalacopus, Spalax).

Rotation-thrust diggers

Fossorial mammals that dig via humeral rotation using broad, shovel-like forefeet equipped with broad, dorso-ventrally compressed claws.

Patagium

A thin, membranous extension of skin stretching between the limbs or wrists and ankles that generates lift for gliding or powered flight.

Natatorial

A fully aquatic swimming lifestyle seen in cetaceans and sirenians, characterized by fused cervical vertebrae, absent hindlimbs and sacrum, and a vestigial pelvic girdle.

Cecum

An intraperitoneal blind pouch located at the junction of the small and large intestines; enlarged in herbivores for housing symbiotic fermenting microbes, but reduced or absent in carnivores.

Hindgut fermentation

A digestive process in which microbial fermentation occurs after the small intestine (in the cecum/colon); characterized by faster food transit, lower nutrient extraction efficiency, and inability to digest microbial protein directly.

Foregut fermentation

A digestive strategy where microbial fermentation occurs before the small intestine (in a multi-chambered stomach/rumen); allows high nutrient extraction efficiency, digestion of microbes, and alkaloid detoxification.

Sanguinivory

A specialized carnivorous dietary adaptation consisting exclusively of feeding on blood, as found in vampire bats.

Folivory

A specialized herbivorous feeding strategy centered entirely or primarily on consuming leaves.

Gummivory

A specialized herbivorous feeding habit that involves consuming tree gums and saps.

Mycophagy

A specialized feeding strategy based on consuming fungi.

Choriovitelline placenta

The primitive, relatively inefficient placenta found in marsupials formed from the yolk sac and chorion, providing limited maternal-fetal attachment.

Chorioallantoic placenta

The eutherian placenta formed from the chorion and allantois, featuring chorionic villi that penetrate deeply into the endometrium for tight vascular exchange.

Embryonic diapause

A reproductive phenomenon occurring in almost all kangaroos where fertilization takes place, but the development of the blastocyst remains temporarily arrested.

Delayed implantation

A reproductive strategy where ovulation, fertilization, and early cleavage occur normally, but blastocyst implantation into the uterine wall is postponed; may be obligate (e.g., armadillos) or facultative (e.g., rodents).

Thermoneutral zone

The range of ambient temperatures between the lower and upper critical temperatures within which a mammal maintains its body temperature with minimal metabolic expenditure.

Nonshivering thermogenesis

Heat production resulting from metabolic biochemical reactions in brown adipose tissue (brown fat) without muscular shivering.

Thermal windows

Sparsely furred or naked areas of the mammalian body surface that can be vascularized to dissipate excess body heat into the environment.

Estivation

A state of dormancy characterized by reduced metabolic activity entered by mammals in response to excessive environmental heat or drought.

Pheromone

A chemical secretion released by an individual that triggers a specific physiological or behavioral response in members of the same species (intraspecific).

Allomone

A chemical communication substance released by an organism that affects the behavior or physiology of a member of a different species (interspecific).