BIOL 329 Lecture Notes - Lecture 5: Evapotranspiration, Ectotherm, Countercurrent Exchange
6 May 2018
School
Department
Course
Professor
Lect 5
Trends in amniotes: usually waterproof skin with keratinized epidermis. Scales, hair, feathers. Costal
ventilation (diaphragm) of the lungs (reduced water loss). Three chambered heart (2 atria, 1 ventricle)
develops partial septum in ventrical to allow some separation of oxygenated and deoxygenated blood
occurs in many reptiles. Septum fully complete in crocodiles, birds and mammals – 4 chambered heart.
Allows higher metabolic rate (de-oxygenated blood pumped directly to lungs).
Thermoregulation:
Ectothermy: external control of body temperature. Amphibian and most living reptiles. Most prevalent
in tropics with high evapotranspiration (warm/wet). Use external sources of heat vs cool conditions
(sun, warm substrate vs shade). Use behavioural strategies to thermoregulate (sitting in sun). Body temp
varies over 24 hours. Generally inactive during darkness (unless warm/wet).
Have complex enzyme systems that allow metabolism at different temperatures (have some to function
at body temps of 5, 10, 15oC, etc.). Often have large and more complex genomes than endotherms.
Endothermy: internal control of body temperature. Birds, mammals, some dinosaurs, some marine
reptiles. Internal heat production and reasonably steady body temperature 37-40oC. Songbirds in NA
durig witer drop their ody teperature at ight so that they do’t lose as uh eergy. Failitated
by feathers, hair, fat, cellular metabolism, counter-current heat exchange. Tuna generate heat in a
structure behind the brain to maintain high brain function. Can be active at all latitudes, all seasons and
throughout day/night cycles. Energetically costly, better at adapting as habitat changes temp can have
larger body size. Pathogen resistance???
Vertebrate endothermy restricts most fungi as potential pathogens.
Metabolic rate in Tetrapods: Increases predictability with increased body mass. Ectotherm daily caloric
intake ___________. Field metabolic rate increases with body mass.
Smaller lizards have to expend more energy/find more food proportionally than large lizards. Mammals:
metabolic rate decreases with size. As you get smaller and smaller birds, they have essentially an infinite
caloric requirement. These cannot exist, therefore there are body size constraints. No birds exist that
weigh less than 1 gram. Lizard and Salamanders: most common body size = 1-10 grams.
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Trends in amniotes: usually waterproof skin with keratinized epidermis. Costal ventilation (diaphragm) of the lungs (reduced water loss). Three chambered heart (2 atria, 1 ventricle) develops partial septum in ventrical to allow some separation of oxygenated and deoxygenated blood occurs in many reptiles. Septum fully complete in crocodiles, birds and mammals 4 chambered heart. Allows higher metabolic rate (de-oxygenated blood pumped directly to lungs). Most prevalent in tropics with high evapotranspiration (warm/wet). Use external sources of heat vs cool conditions (sun, warm substrate vs shade). Use behavioural strategies to thermoregulate (sitting in sun). Have complex enzyme systems that allow metabolism at different temperatures (have some to function at body temps of 5, 10, 15oc, etc. ). Often have large and more complex genomes than endotherms. Internal heat production and reasonably steady body temperature 37-40oc. Songbirds in na duri(cid:374)g wi(cid:374)ter drop their (cid:271)ody te(cid:373)perature at (cid:374)ight so that they do(cid:374)"t lose as (cid:373)u(cid:272)h e(cid:374)ergy.
