BIOL 111 Lecture Notes - Lecture 20: Theropoda, Convergent Evolution, Respiratory System

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9 Aug 2016
Lecture 20: Birds (Aves)
To occupy extreme and/or variable environments, birds use thermoregulation = body
temp. control
Shared characteristics between birds and dinosaurs:
- bipedal
- carnivorous
- 4-chambered heart
- Etc.
- feathers and wings = bird characters
- teeth and bony tail = non-avian characters
Birds (Aves)
- amniotes
- endothermic
- 4-chambered heart
- Feathers
Source of body heat
- ectotherms: absorb external heat
- endotherms: generate own internal heat via metabolic processes
How endotherms generate heat: Less efficient at transforming energy
Temporal variation of body temp.
- homeotherm: keep temperature constant
- heterotherm: body temperature depends on environmental temp.
How metabolic rates of endo- and ectotherms respond to different temperatures
Metabolic rate = sum of energy expenditures per unit of time
- mouse: endotherm
- lizard: ectotherm
- *thermoneutral zone: most effective zone of thermoregulation
In the field, a lizard maintains body temp. at a different temp. than environment
Hummingbird = endotherm, heterotherm.
Behavioural thermoregulation = lizard maintains body temp. between upper and lower
limits by moving between hot and cold microhabitats.
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