Lecture 33 Amniotes - Birds

Question 1

what are birds?

Answer 1

• class Aves
• archosaurs
• “modern branch of dinosaurs”
• every feature of their reptilian anatomy has undergone modification in their adaptation to flight

Question 2

where did birds probably evolve from?

Answer 2

small theropods – group of carnivorous dinosaurs

- many fossils from china show theropods with feathers

Question 3

what may have caused early feathers to occur?

Answer 3

• thermoregulation – insulation
• increased mobility – lift while jumping, traction running up hills
• camouflage
• courtship display

Question 4

what is the oldest known birds?

Answer 4

• archaepteryx - feathers and wings – powered flight, teeth, bony tails, wing, claws

Question 5

what are derived characters of birds?

Answer 5

• wings with keratin feathers
• lightweight hollow bones with large air filled cavities and honeycombed structure
• horny beaks that lack teeth
• digestive system adapted for flight (crop for storage, gizzard that has swallowed stones for grinding food)
• reduced organs (small gonads, one ovary, no bladder)
• reduced wight
• high metabolic rate supported by: 4-chambered heart, complex respiratory system, endothermic

Question 6

what are feathers?

what are wings?

Answer 6

F: finely subdivided keratinous scales that are homologous
W: evolved tetrapod forelimbs, no claws

Question 7

what is the complex respiratory system of birds?

Answer 7

• air cycles between air spaces in the bones and lungs, lungs receive fresh air during both inhalation and exhalation

Question 8

how are birds endothermic?

Answer 8

• use metabolic energy to maintain body temperature
• enables high rate of metabolism
• feathers and layer of fat retain body heat
• birds and mammals are the only endothermic animal groups

Question 9

what are characteristics of modern birds?

Answer 9

• internal fertilization – most DON’T HAVE intromittent organs (only few)
• cloaca – common opening for digestive, urinary and reproductive tracts – m&f press cloaca together to transfer sperm
• ## eggs with a hard calcareous shell

Question 10

what are feathers, again?

Answer 10

• characteristic feature of birds that facilitate flight, provide insulation, used in display, camouflage, signalling
• require maintenance and preening – moves waxy sextion from gland at base of tail to rest of feathers – keeps supple, microbacterial agent; zips up flight and contour feathers – hooks and rays link together
• removes foreign particles
• plumage is regularly moulted

Question 11

what are characteristics of modern birds?

Answer 11

• internal fertilization – most DON’T HAVE intromittent organs (only few)
• cloaca – common opening for digestive, urinary and reproductive tracts – m&f press cloaca together to transfer sperm
• eggs with a hard calcareous shell
• terrestrial, freshwater, marine but all come to land to breed
• predators, herbivores, scavengers, omnivores – usually can tell by feet and beaks
• most can fly – flightlessness evolved independently many times
• some form of parental care
• young are cared by mother or both parents

Question 12

what are feathers, again?

Answer 12

• characteristic feature of birds that facilitate flight, provide insulation, used in display, camouflage, signalling
• require maintenance and preening – moves waxy sextion from gland at base of tail to rest of feathers – keeps supple, microbacterial agent; zips up flight and contour feathers – hooks and rays link together
• removes foreign particles
• plumage is regularly moulted

Question 13

what does precocial mean?

Answer 13

• young may be able to feed selves

Question 14

what does altricial mean?

Answer 14

• young may be born helpless and featherless