Lecture 17: Dinosaur Metabolism Flashcards
What is ectothermy?
Cold bloodedness
What is endothermy?
Warm bloodedness
Why are ectothermy and endothermy more meaningful?
A cold blooded animal can move into the sun and heat up considerably and is not cold blooded anymore
These terms refer to:
Body temperature regulation
Variation in body temperature
level of resting metabolism
Body temperature regulation: Endothermy
Endothermic organisms regulate their body temperature internally and maintain a nearly constant temperature no matter what the conditions are like outside the body
Body temperature regulation: ectothermy
Ectothermic organisms regulate their temperature externally and the body temperature responds directly to temperatures of the environment. An ectotherm regulates body temperature by moving itself to an environment that will allow the animal to heat up cool down, does not use internal biological processes
What is homeotherm?
organism in which the internal body temperature remains constant
what is a poikilotherm?
organism in which the internal body temperature varies
What are ectothermic poikilotherms?
most modern reptiles
What are endothermic poikilotherms?
bats and hummingbirds
what are endothermic homeotherms?
humans
Endothermy is not superior or inferior to ectothermy
2 metabolic strategies which are suited to different anatomies and behaviors
Resting Metabolism
Metabolism: level of internal activity, meaning cellular respiration and burning food calories. Resting metabolism- level of internal activity when animal is at rest
What is tachymetabolic?
an animal whose metabolism remains at a high level, burning calories, metabolic functions at high place, typically but not always endotherms
What is bradymetabolic?
An animal whose metabolism slows to a low level of activity when resting, typically but not always ectotherms
basic biology of metabolism
Metabolism is the process by which all organisms harvest energy and employ it to drive chemical reactions. Metabolism takes place in form of cellular respiration, a process by which the energy stored in a glucose molecule is released by oxidation
What is cellular respiration
breakdown of carbohydrates (sugar) if broken through oxidation energy is released, ATP breaks down into ADP and energy. Heat production when energy is released, point of maximum rate of oxygen consumption, when exceeded lactic acid forms within cells, detrimental to organisms when in great concentrations
Anaerobic Metabolism
Takes place when amount of oxygen supplied through breathing is insufficient, glycosis sets in to produce energy. Production of pyruvic acid-lactic acid- muscle pain
Metabolism in ectotherms vs. Endotherms
Endotherms and ectotherms vary in regard to the onset of anaerobic metabolism. An endotherms resting rate is approx. where an ectotherms point of lactic formation occurs. Endotherms are therefore capable of higher level of activity sustained over longer periods of time than are their ectothermic counterparts
Will ectotherms or endotherms generally be more numerous?
Ectotherms, because endotherms cost more energetically to maintain
Anatomical evidence
Posture and gait: upright-endotherms, fine neuromuscular control to maintain upright posture, evolution of fully erect posture linked to activity level of endothermy, long leggedness and bipedalism Speed levels of activity and agility- slender flexible limb joints, balancing tails, high active and agile animals, consistent with endothermic metabolism. Brains (encephalization quotient (EQ) (brain size and EQ exceed that of modern lizards Feeding adaptations Body Size (small dinosaurs vs. large dinosaurs)
Body size
were large dinosaurs mass homeotherms? maintaining a constant temperature
Gigantotherms? maintaining relatively constant temperature bc of their larger size
Gigantotermy
modified mass homeothermy, large size and relatively slow metabolic rates, control of blood circulation in peripheral tissue, low surface to voulme ratios retains heat, problem of overheating
Histological Evidence?
Bone Microstructure: Haversian bone, as organisms grow their bones grow with them, bones grow through remodeling, resorption of primary bone, redeposition of secondary bone
Haversian bone
It is secondary bone has vascular canals, haversian canals, dense haversian bone is only found in endotherms, modern mammals and birds
Haversian bone in fossils
Dinosaurs, pterosaurs, advanced synapsids (mammals), a variety of factors is responsible for haversian bone: age, nutrients, stress
Bone growth
Lines of arrested growth (LAG’s) bands in bone- yearly increments. In modern ectotherms Lag’s grow when growth stops due to temperature fluctuations caused by seasonality, not well developed due to preferred regions
Growth rates in dinosaurs
Comparison of dense haversian bone with overall limb development.
Maiasaura: 3 M per year
LAG’s are in many dinosaurs, responding to seasonally induced temp. changes, lags have not been correlated with climate change yet
Ecological evidence
Predatory endotherms need more food, predatory ectotherms need less food. Predator-prey ratio for endothermic predators is lower. Dinosaurian communities had low ratio.
Zoogeographic evidence
Modern ectotherms restricted to tropical regions, dinosaurs migrated in colder regions.
Phylogenetic evidence
Endotherms have insulation: feathers/fur. So why would the early feathered animals develop insulation when they were ectotherms? A prerequisite for endothermy is a four chamber heart, high blood pressure, provision of high oxygenated blood separated from deoxygenated blood
Geochemical evidence
oxygen isotope compositions vary with temperature, oxygen isotope composition of bone, measuring the temperature when bone formed.
Geochemical evidence in ectotherms vs endotherms
Ectotherms: temperature difference between bones in the centre of skeleton and in the extremities
Endotherms: even temperature through circulating fluids of constant temperature
Research on T rex bones
Temperature difference of 4 degrees or less,was T rex endothermic? Problems: recrystallization of bone, T rex was mass homeotherm rather than true endotherm
Active theropods and ornithopods were _____
endothermic, others ectothermic?
Sauropods and other large dinosaurs were mass homeotherms or ______ as adults
Gigantotherms
