Lecture 17: Dinosaur Metabolism

Question 1

What is ectothermy?

Answer 1

Cold bloodedness

Question 2

What is endothermy?

Answer 2

Warm bloodedness

Question 3

Why are ectothermy and endothermy more meaningful?

Answer 3

A cold blooded animal can move into the sun and heat up considerably and is not cold blooded anymore

Question 4

These terms refer to:

Answer 4

Body temperature regulation
Variation in body temperature
level of resting metabolism

Question 5

Body temperature regulation: Endothermy

Answer 5

Endothermic organisms regulate their body temperature internally and maintain a nearly constant temperature no matter what the conditions are like outside the body

Question 6

Body temperature regulation: ectothermy

Answer 6

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

Question 7

What is homeotherm?

Answer 7

organism in which the internal body temperature remains constant

Question 8

what is a poikilotherm?

Answer 8

organism in which the internal body temperature varies

Question 9

What are ectothermic poikilotherms?

Answer 9

most modern reptiles

Question 10

What are endothermic poikilotherms?

Answer 10

bats and hummingbirds

Question 11

what are endothermic homeotherms?

Answer 11

humans

Question 12

Endothermy is not superior or inferior to ectothermy

Answer 12

2 metabolic strategies which are suited to different anatomies and behaviors

Question 13

Resting Metabolism

Answer 13

Metabolism: level of internal activity, meaning cellular respiration and burning food calories. Resting metabolism- level of internal activity when animal is at rest

Question 14

What is tachymetabolic?

Answer 14

an animal whose metabolism remains at a high level, burning calories, metabolic functions at high place, typically but not always endotherms

Question 15

What is bradymetabolic?

Answer 15

An animal whose metabolism slows to a low level of activity when resting, typically but not always ectotherms

Question 16

basic biology of metabolism

Answer 16

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

Question 17

What is cellular respiration

Answer 17

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

Question 18

Anaerobic Metabolism

Answer 18

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

Question 19

Metabolism in ectotherms vs. Endotherms

Answer 19

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

Question 20

Will ectotherms or endotherms generally be more numerous?

Answer 20

Ectotherms, because endotherms cost more energetically to maintain

Question 21

Anatomical evidence

Answer 21

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)

Question 22

Body size

Answer 22

were large dinosaurs mass homeotherms? maintaining a constant temperature
Gigantotherms? maintaining relatively constant temperature bc of their larger size

Question 23

Gigantotermy

Answer 23

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

Question 24

Histological Evidence?

Answer 24

Bone Microstructure: Haversian bone, as organisms grow their bones grow with them, bones grow through remodeling, resorption of primary bone, redeposition of secondary bone

Question 25

Haversian bone

Answer 25

It is secondary bone has vascular canals, haversian canals, dense haversian bone is only found in endotherms, modern mammals and birds

Question 26

Haversian bone in fossils

Answer 26

Dinosaurs, pterosaurs, advanced synapsids (mammals), a variety of factors is responsible for haversian bone: age, nutrients, stress

Question 27

Bone growth

Answer 27

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

Question 28

Growth rates in dinosaurs

Answer 28

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

Question 29

Ecological evidence

Answer 29

Predatory endotherms need more food, predatory ectotherms need less food. Predator-prey ratio for endothermic predators is lower. Dinosaurian communities had low ratio.

Question 30

Zoogeographic evidence

Answer 30

Modern ectotherms restricted to tropical regions, dinosaurs migrated in colder regions.

Question 31

Phylogenetic evidence

Answer 31

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

Question 32

Geochemical evidence

Answer 32

oxygen isotope compositions vary with temperature, oxygen isotope composition of bone, measuring the temperature when bone formed.

Question 33

Geochemical evidence in ectotherms vs endotherms

Answer 33

Ectotherms: temperature difference between bones in the centre of skeleton and in the extremities Endotherms: even temperature through circulating fluids of constant temperature

Question 34

Research on T rex bones

Answer 34

Temperature difference of 4 degrees or less,was T rex endothermic? Problems: recrystallization of bone, T rex was mass homeotherm rather than true endotherm

Question 35

Active theropods and ornithopods were _____

Answer 35

endothermic, others ectothermic?

Question 36

Sauropods and other large dinosaurs were mass homeotherms or ______ as adults

Answer 36

Gigantotherms