Mammals Lab

poikilothermy

- a pattern of temperature regulation characterized by large variations in body temperature that are due to changing environmental conditions. - most ectotherms are poikilothermic.

sweating

an active process stimulated by the sympathetic nervous system to cause evaporative heat loss from the skin.

Thick fur

- Thick dense fur traps a layer of warm air near the skin and/or thick layers of adipose tissue (fat) insulates their bodies.

ectothermic animal (ectotherm)

- an animal that derives most of its body heat from external sources such as solar radiation. - cold blooded animals - most invertebrates, some fish, amphibians and some reptiles.

endothermic animal (endotherm)

- an animal that derives most of its body heat from its own internal metabolism. - warm blooded animals. - some fish and reptiles and all birds and mammals are endotherms.

body temperatures

- are affected by both internal metabolic changes (disorders, hormones, changes related to exercise) and external environmental factors (heat or cold).

mammal characters part 2

- complete digestive system with an anus, no cloaca in most mammals. - monotremes (platypus and echidna) that lay eggs retain a cloaca - monotremes = one hole - urogenital systems are separated from digestive tract (separate urethra and anus) in all mammals except monotremes (order monotremata) - closed circulatory system with a 4 chambered heart (2 atria and 2 ventricles) - mammals have a 4 chambered heart with 2 separate ventricles and fully developed inter-ventricular septum, the therapsids that evolved into mammals may have also had a 4 chambered heart - best hearing on earth, even more developed senses, keen olfactory (smell) snse eyes, hearing, olfaction, equilibrium (balance) via inner ear structures - mammals are dioecious with much social interaction and parental care (K selected) - direct development (no larvae produced).

other physiological mechanisms.

- cooling and heating rates are not always equal as they would for passive body .

An animal's body decreases heat production and increases heat loss by:

- decreasing muscle tone (tension) - sweating - vasodilation of blood vessels in the skin - decreasing voluntary exercise (you get too hot) = behavioral thermoregulation - moving to shady or cooler area = behavioral thermoregulation

homeothermic animal (homeotherm)

- endothermic animal that maintains a very consistent body temperature within a very narrow temperature range. - birds and mammals are usually strict homeotherms. - humans are homeotherms.

mammal characters:

- first synapsid reptile ancestors appear in the late carboniferous period, many mammal like synapsid reptiles in the triassic and today's mammal lineage split up in the jurassic period. - mammals evolved most directly from therapsid and cynodont ancestors (both synapsids) - mammary glands present to produce nutritious milk for young - hair present in most but reduced or absent in cetaceans. hair evolved from reptile scales, mammals do not possess scales - heterodontous dentition = different kinds of teeth (incisors, canines, premolars and molars) to chew their food more effectively extract nutrients (key for big brain and endothermy) - strong and robust musculoskeletal system with four limbs (tetrapods) - all mammals have 7 cervical (neck) vertebrae - basic skeletal body plan similar but many variations based on habitat and feeding ecology - possess an amnion = membrane that surrounds and protects the embryo and allows them to lay their eggs entirely in the terrestrial environment - lungs in adults and young for breathing, no larvae = direct development - more advanced kidneys than reptiles, urea in the primary nitrogen waste product

advantages & disadvantages to being small

- heat is gained and lost faster - because heat is lost faster, animal has to eat faster to replace lost heat quickly

advantages & disadvantages to being large

- heat is gained and lost more slowly - because heat is lost more slowly, the animal doesn't have to replace lost heat as quickly therefore it doesn't have to eat as much compared to its body weight

more evolved characteristics unique to mammals

- heterodont teeth (specialized for chewing by mechanically breaking down food to speed up digestion and releasing the energy needed to produce heat).

An animal's body increases heat production and decreases heat loss by:

- increasing muscle tone (tension) - shivering - vasoconstriction of blood vessels in the skin - non-shivering thermogenesis (increased fat metabolism) - voluntary exercise (behavioral response eg stomping feet) = behavioral thermoregulation - changes in posture to reduce exposure to the environment = behavioral thermoregulation - move to warmer area = behavioral thermoregulation

Secondary palate

- not found in pelycosaurs - found in cynodonts and mammals.

effect of animal size on thermal regulation

- small bodies heat up and cool down faster - bigger and thicker bodies heat up and cool down slower. - smaller/thinner bodies have a larger surface area to volume ratio.

Modern mammals

- synapsids. - descendants of a group called cynodonts (appeared in the late Permian period) < ancestors of mammals

core temperature

- the temperature of thoracic and abdominal organs, temperature which is most closely monitored and maintained.

hyperthermia

Abnormally high body temperature

hypothermia

abnormally low body temperature

inertial homeothermy

constant temperature due to large body size (heating and cooling of large mass) - oceans, dinosaurs, leatherback sea turtles.

heat stroke

dangerous breakdown in hypothalamic regulatory pathways caused by excessive BT in a hot, humid environment.

Non mammalian synapsids

divided into two groups: - pelycosaurs - therapsids

key characteristic of synapsids

endothermy

panting

for cooling, airflow over nasal conchae/turbinates which are filled with blood

thigmothermy

obtaining heat from the substrate

heliothermy

obtaining heat from the sun