Lecture 20

Question 1

How to occupy extreme environment?

Answer 1

Thermoregulation

Question 2

How to get into the air?

Answer 2

Feathers, better lungs, lighter bones
- Not only species to fly but only one in lien of vertebrates
Phylogenetically descendants of reptiles/dinosaurs

Question 3

Ancestor to Birds (shared characteristics)

Answer 3

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

Question 4

Archaeopteryx (Ancient wing)

Answer 4

• 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

Question 5

special about bird

Answer 5

feathers

more efficient heart

Question 6

Bird: Aves (How many species, circulation, types, feathers (2)) (5)

Answer 6

• 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)

Question 7

Diversity of beaks evolve quickly (Darwin’s finches)

Answer 7

• adaptive radiation

- 14 different beak forms

Question 8

Body Temperature Control = Thermoregulation

Answer 8

altering:
1. Radiation
2. Evaporation
3. Convection
4. Conduction

Question 9

Ectotherms

Answer 9

absorbs external heat

Question 10

Two types of body heat

Answer 10

Ectotherms

Endotherms

Question 11

Endotherms

Answer 11

generates own internal heat with metabolic processes

Question 12

How do endotherms generate heat?

Answer 12

Inefficient Energy transformation (lose E as heat when converting food into ATP or ATP into ADP)

Question 13

Homotherm

Answer 13

Constant temperature

Question 14

Heterotherm

Answer 14

variable temperature

Heterotherm are most likely ectotherms because outside environment regulates heat

Question 15

Hibernation

Answer 15

metabolic rate & temperature decreases

Question 16

Homotherm/Heterotherm

Answer 16

Most organisms are a mixture of ecto/endo/homeo/hetero but mammals & birds = endotherms; insects, reptiles, amphibians = ectotherms

Question 17

How metabolic rates (MR) of endo and ectotherms respond to different temperatures in lab?
Metabolic rate: sum of all energy expenditures

Answer 17

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

Question 18

Mechanisms to maintain body temperature

Answer 18

1. Behavioral - orientation relative to heat source
   (Feathers originally evolved for insulation, early bird/ theropod dinosaurs have feathers on legs)
2. Physiological - too hot (increase blood flow to periphery, sweating, panting); too cold (lower blood flow to periphery)
3. Physical: insulation, surface area; volume ratio, colour

Question 19

Better Respiration - Birds than Human

Answer 19

• 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

Question 20

Evolution of Flight

Answer 20

Flight evolved 4 times: insects, pterosaurs, birds, bats (not the same thing as gliding)

Question 21

Convergent evolution

Answer 21

similarities due to common environment not common ancestor

Question 22

Adaptation for flight:

Answer 22

• 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

Question 23

How do wings enable flight?

Answer 23

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

Question 24

Generate lift from flying

Answer 24

Top: lower pressure, higher speed
Bottom: higher pressure, lower speed