How to occupy extreme environment?
Thermoregulation
How to get into the air?
Feathers, better lungs, lighter bones
- Not only species to fly but only one in lien of vertebrates
Phylogenetically descendants of reptiles/dinosaurs
Ancestor to Birds (shared characteristics)
Theropod Dinosaur - Birds are dinosaurs because direct descendants of dinosaurian ancestors Shared Characteristics: - Bipedal - 3 hind toes - Carnivores - 4 chambered heart - similar lungs (to each other) - feathered (exclusive to birds/dinosaurs) - Hollow Bones - parental care of eggs & juveniles
Archaeopteryx (Ancient wing)
- 150 mya (Jurassic period) with 12+ fossil specimens
- Early bird but NOT ancestor of modern birds
- Crow-sized early bird evolved from therapod dinosaurs
- Avian (bird) characteristics: feathers & wings
special about bird
feathers
more efficient heart
Bird: Aves (How many species, circulation, types, feathers (2)) (5)
- 9,600 species (most accurate #)
- Amniotes: use amniotic egg & uric acid & endothermic
- 4 chambered heart (completely separate pulmonary & systemic circuits)
- Feathers & most fly but some secondary losses of flight
- Diverse beaks = diverse diets (carnivores, herbivores, nectivores)
Diversity of beaks evolve quickly (Darwin’s finches)
- adaptive radiation
- 14 different beak forms
Body Temperature Control = Thermoregulation
altering:
1. Radiation
2. Evaporation
3. Convection
4. Conduction
Ectotherms
absorbs external heat
Two types of body heat
Ectotherms
Endotherms
Endotherms
generates own internal heat with metabolic processes
How do endotherms generate heat?
Inefficient Energy transformation (lose E as heat when converting food into ATP or ATP into ADP)
Homotherm
Constant temperature
Heterotherm
variable temperature
Heterotherm are most likely ectotherms because outside environment regulates heat
Hibernation
metabolic rate & temperature decreases
Homotherm/Heterotherm
Most organisms are a mixture of ecto/endo/homeo/hetero but mammals & birds = endotherms; insects, reptiles, amphibians = ectotherms
How metabolic rates (MR) of endo and ectotherms respond to different temperatures in lab?
Metabolic rate: sum of all energy expenditures
Behavioral thermoregulation
- Lizard maintains its body temperature between upper & lower limits by moving btwn hot & cold microhabitats; critically important for ectotherms
Also done to a degree by endotherms
Mechanisms to maintain body temperature
- Behavioral - orientation relative to heat source
(Feathers originally evolved for insulation, early bird/ theropod dinosaurs have feathers on legs) - Physiological - too hot (increase blood flow to periphery, sweating, panting); too cold (lower blood flow to periphery)
- Physical: insulation, surface area; volume ratio, colour
Better Respiration - Birds than Human
- Flying & endothermy demand high levels of O2
- System more complex & efficient than mammals (Respiratory system: Unidirectional air flow through lungs, 8-9 air sacs (anterior & posterior) replace all air in lungs with every 2 breaths
Humans: Tidal flow; air goes in & back out way it came, don’t get rid of all air in lungs
In Birds: - Breath 1 = air drawn into posterior air sacs & propelled through lung (inhale)
- Breath 2: same air drawn into anterior air sacs (inhale), propel out through nares (exhale)
- Takes 2 cycles for breath of air to go in & out; circular flow instead of tidal flow
Evolution of Flight
Flight evolved 4 times: insects, pterosaurs, birds, bats (not the same thing as gliding)
Convergent evolution
similarities due to common environment not common ancestor
Adaptation for flight:
- Hollow bones (lighter)
- Sternum enlarged & keeled (increases surface area to attach large flight muscles)
- Feathers (used for insulation, flight, sensory structures, lining nests; made of keratin (derived from scales)
- most birds have reptile-like, scaled skin on legs not feathers
How do wings enable flight?
Change air flow pattern & creates lift (like airplane)
- Particles must move faster to get over bump made by shape of wing (flow at different rate & bottom): creates different air densities, accelerate flow around airfoil & creates lift
Generate lift from flying
Top: lower pressure, higher speed
Bottom: higher pressure, lower speed
