Birds I: Evolutionary origins and diversification of birds

Question 1

Characterise a bird

Answer 1

• c. 11 000 species recognised
• endothermic (high metabolic rate)
• feathers (structurally highly modifiable)
• flight
• eggs
• bones
• keratinaceous beak
• no teeth

Question 2

Birds are the

Answer 2

most diverse terrestrial vertebrate group

Question 3

Discuss the endothermic range of birds

Answer 3

40-42 ̊C

Question 4

Discuss powered flight in birbs

Answer 4

• 98% of species capable
• flight is a basal character

Question 5

Discuss bird eggs

Answer 5

• hard-shelled
• laid into a nest where they receive parental care
• > 90% of cases by both sexes of parent

Question 6

Discuss bird bones

Answer 6

• light
• pneumatized (air-filled)

Question 7

Describe Archaeopteryx

Answer 7

• Jurassic - c.150Mya

Question 8

Feathers vs Flight

Answer 8

feathers pre-date the evolution of flight, so cannot initially have evolved in order to aid flight

Question 9

Discuss parental care in birds

Answer 9

• theropods brooded eggs as modern birds (unlike any other reptile)
• parental care in birds may be an ancestral character

Question 10

Describe the Jehol biota from NE China

Answer 10

• exceptional preservation
• 130-120MYA

Question 11

Describe the Enantiornithines

Answer 11

• major Cretaceous radiation
• 90+ genera
• > 50% of Cretaceous birds
• largely arboreal
• initially toothed jaw: evolved beak by Late Cretaceous
• unique feather structures
• bone structure shows slow growth, overlapping reproduction (unlike crown group birds)
• none survived past end Cretaceous

Question 12

Explain why birds have a relatively poor fossil record

Answer 12

• small size
• light
• pneumatized bones

Question 13

Describe Asteriornis skull morphology

Answer 13

• left nasal
• left quadrate
• mesethmoid
• right mandible
• left mandible
• jugal
• basisphenoid

Question 14

Describe Asteriornis phylogeny

Answer 14

• close affinities with both Anseriforms (waterfowl) and Galliforms (chickens etc)
• 66.8 Mya
• just before K-T boundary
• Neognathae?

Question 15

Summarise bird evolution

Answer 15

• Passeridae diversified most recently
• raptorial life-history evolved multiple times independently
• multiple evolutions of aquatic life-style
• multiple origins of vocal learning in birds
• two older clades of ‘modern’ birds: Palaeognathae (~95MYA) and Galloanseres (~80 MYA)

Question 16

Describe the Passeridae

Answer 16

• most diverse clade of birds
• finches, warblers, crows etc

Question 17

raptorial life history

Answer 17

• obligatory predatory behaviour
• falcons, hawks, owls

Question 18

List some aquatic birds

Answer 18

flamingo, waders, pelicans, ducks

Question 19

Describe some vocally learning birds

Answer 19

songbirds, parrots, hummingbirds

Question 20

Describe the Palaeognathae

Answer 20

• rather few species
• flightless or poorly flying
• Ratites
• Tinamous
• ‘Gondwanan origin’: extant species all S Hemisphere
• ‘primitive’ birds: semi-differentiated sex chromosomes
• recently extinct members

Question 21

List some Ratites

Answer 21

ostrich, rhea, cassowary, emu, kiwi

Question 22

Describe the Tinamous

Answer 22

• 47 species in S America, Mexico, Central & South America

Question 23

Give some extinct Palaeognathae

Answer 23

• Aepyornis: Elephant Bird
• Moas: New Zealand

Question 24

Describe the evolutionary origins of the ratites

Answer 24

• mostly post K/T boundary
• multiple cases of independent evolution of the ratite life history
• potentially niche expansion post extinction of dinosaurian herbivores

Question 25

Describe ratites

Answer 25

• not monophyletic
• include the flying Tinamous
• either flight lost at least three times independently
• OR regained in Tinamous
• current hypothesis: early ratites flew
• loss of flight response to freeing of terrestrial niches vacated by dinosaurs
• repeated convergent evolution

Question 26

Describe the restricted body form of a bird compared with other vertebrate group

Answer 26

• log5 variation in body weight (2-2x10^5g)
• bee hummingbird and ostrich

Question 27

Give some extinct bird weights

Answer 27

• Dromornis stirtoni: 500kg (Australia to c. 30 KYBP)
• Dinornis: New Zealand (c. 500y bp)

Question 28

Give the body weight variation of mammals

Answer 28

• 1.5 - 1.5 × 10^8 g
• 6 log units

Question 29

Give the body weight variation of reptiles

Answer 29

• 0.2 - 2 × 10^6 g
• 7 log units

Question 30

Give the body weight variation of fishes

Answer 30

• 0.001 - 1.3 × 10^7 g
• 10 log units

Question 31

Give the body weight variation of amphibians

Answer 31

• 0.02 - 7 × 10^4 g
• 6.5 log units

Question 32

Describe variance in reproductive biology

Answer 32

Birds: all obligately oviparous
Mammals: placental/non-placental/oviparous
Fishes: both oviparous and placental
Reptiles: both oviparous and placental

Question 33

Give birds altitudinal range

Answer 33

• Ruppell’s vulture: 11.3 km
• king penguin: -0.5 km
• largest range of any animal class

Question 34

Give birds altitudinal breeding range

Answer 34

• alpine chough 5.8 km
• house sparrow -0.6km
• largest range of any animal class

Question 35

Give birds geographical range

Answer 35

• kittiwake at 89° 58’ N
• south polar skua at 90° S
• largest range of any animal class

Question 36

Describe the chicken genome

Answer 36

• female Heterogamy (female ZW, male ZZ)
• macro- and micro- chromosomes

Question 37

Give bird genome characteristics

Answer 37

• 20-23000 genes
• small (1.05bn bp)
• many fewer repetitive elements (10%)
• 2-20 fold higher rate of recombination
• conserved