birds (aves)

the ancestor of birds was likely a theropod (dinosaur). what are 7 shared characteristics of these two groups?

• bipedal, similar feet

• carnivorous

• 4-chambered heart

• similar lungs

• feathered!

• hollow bones

• parental care of eggs and juveniles

describe the archaeopteryx

• about 150 mya (jurassic)

• crow-sized

• feathers+wings - bird characters

• teeth+bony tail - nonbird characters

what are aves’ characteristics

• amniotes

• endothermic - thermoregulation

• 4-chambered heart

• feathers

• most fly

• diverse beaks

• diverse feet

• specialized respiration and ventilation

whats an amniote

organisms that produce amniotic eggs - which are eggs that can withstand dry environment without suffering from desiccation

name the two types of body heats in vertebrates, provide an example for each

1. ectothermic: absorb external heat, ex. bees

2. endothermic: generate their own internal heat throguh metabolic processes, ex. bears

name the two types of thermoregulation in vertebrates, provide an example for each

homeothermy: ability to maintain a constant temperature, ex. mouse

heterothermy: variable temperature, ex. lizards

list three types of thermoregulation mechanisms

1. behavioural

2. physiological

3. physical

describe behavioural thermoregulation, provide examples

• orientation relative to heat source

• basking, huddling and varying contact with heat surface

• moving locations throughout the day

• ex. lizards maintain body temp between upper and lower limits by moving between hot and cold microhabitats

• ex. penguins huddling together for body heat

describe physiological thermoregulation

• too hot: increase blood flow to periphery, sweating (evaporative cooling), panting

• too cold: decrease blood flow to periphery, shiver (metabolic heat)

• in hypothalamus: negative feedback system

describe physical thermoregulation, provide examples

• insulation (fur, feathers, fat)

• surface area<volume

• colour

• ex. jack rabbits vs arctic hares

• countercurrent heat exchangers

  • ex. whale tongue, mammal foot, brown adipose tissues

describe avian respiration

• flying and endothermy demand high amount of oxygen

• system much more complex and efficient than mammals

• system:

  • numerous air sacs (8-9): anterior and posterior

  • unidirectional flow of air through lungs (vs. us that have tidal air flow: in and out)

• takes 2 cycles for any breath of air to go in and out

  • breath 1: air drawn into posterior air sacs, air propelled through the lung

  • breath 2: same air drawn into anterior air sacs

  • same air is propelled out through nares

how many times has flight evolved, name each group that evolved

4 times

1. insects

2. pterosaurs

3. birds

4. bats

Note: flying is different than gliding

what is convergent evolution? provide an example

• independant evolution from different lineages, all end up evolving the same trait due to the selection/environment

ex. wings are evolved across many lineages, but evolved independantly

list 3 adaptations “for” flight

• hollow bones

• sternum enlarged and keeled: increases SA for attachment of flight muscles (large pectoral muscles)

• feathers

what are feathers’ functions?

• insulation

• flight

• sensory structures

• lining nests

what are feathers derived from? what are they made of?

• evolved from scales (reptiles!)

• composed of beta-”keratin”

• most birds have reptile-like scaled skin on their legs

what were the two hypotheses of how flight evolved from the ground? which is more likely, why?

1. tree-down: jump from trees, flap their arms and survived better

2. ground-up: hatchlings run from danger, often steep inclines, flapping their wings, angle of wing flapping created traction rather than lift

• likely ground-up, based on species’ ancestors of those that can fly now