Birds I: Evolutionary origins and diversification of birds Flashcards
Characterise a bird
- c. 11 000 species recognised
- endothermic (high metabolic rate)
- feathers (structurally highly modifiable)
- flight
- eggs
- bones
- keratinaceous beak
- no teeth
Birds are the
most diverse terrestrial vertebrate group
Discuss the endothermic range of birds
40-42 ̊C
Discuss powered flight in birbs
- 98% of species capable
- flight is a basal character
Discuss bird eggs
- hard-shelled
- laid into a nest where they receive parental care
- > 90% of cases by both sexes of parent
Discuss bird bones
- light
- pneumatized (air-filled)
Describe Archaeopteryx
- Jurassic - c.150Mya
Feathers vs Flight
feathers pre-date the evolution of flight, so cannot initially have evolved in order to aid flight
Discuss parental care in birds
- theropods brooded eggs as modern birds (unlike any other reptile)
- parental care in birds may be an ancestral character
Describe the Jehol biota from NE China
- exceptional preservation
- 130-120MYA
Describe the Enantiornithines
- 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
Explain why birds have a relatively poor fossil record
- small size
- light
- pneumatized bones
Describe Asteriornis skull morphology
- left nasal
- left quadrate
- mesethmoid
- right mandible
- left mandible
- jugal
- basisphenoid
Describe Asteriornis phylogeny
- close affinities with both Anseriforms (waterfowl) and Galliforms (chickens etc)
- 66.8 Mya
- just before K-T boundary
- Neognathae?
Summarise bird evolution
- 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)
Describe the Passeridae
- most diverse clade of birds
- finches, warblers, crows etc
raptorial life history
- obligatory predatory behaviour
- falcons, hawks, owls
List some aquatic birds
flamingo, waders, pelicans, ducks
Describe some vocally learning birds
songbirds, parrots, hummingbirds
Describe the Palaeognathae
- 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
List some Ratites
ostrich, rhea, cassowary, emu, kiwi
Describe the Tinamous
- 47 species in S America, Mexico, Central & South America
Give some extinct Palaeognathae
- Aepyornis: Elephant Bird
- Moas: New Zealand
Describe the evolutionary origins of the ratites
- mostly post K/T boundary
- multiple cases of independent evolution of the ratite life history
- potentially niche expansion post extinction of dinosaurian herbivores
Describe ratites
- 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
Describe the restricted body form of a bird compared with other vertebrate group
- log5 variation in body weight (2-2x10^5g)
- bee hummingbird and ostrich
Give some extinct bird weights
- Dromornis stirtoni: 500kg (Australia to c. 30 KYBP)
- Dinornis: New Zealand (c. 500y bp)
Give the body weight variation of mammals
- 1.5 - 1.5 × 10^8 g
- 6 log units
Give the body weight variation of reptiles
- 0.2 - 2 × 10^6 g
- 7 log units
Give the body weight variation of fishes
- 0.001 - 1.3 × 10^7 g
- 10 log units
Give the body weight variation of amphibians
- 0.02 - 7 × 10^4 g
- 6.5 log units
Describe variance in reproductive biology
Birds: all obligately oviparous
Mammals: placental/non-placental/oviparous
Fishes: both oviparous and placental
Reptiles: both oviparous and placental
Give birds altitudinal range
- Ruppell’s vulture: 11.3 km
- king penguin: -0.5 km
- largest range of any animal class
Give birds altitudinal breeding range
- alpine chough 5.8 km
- house sparrow -0.6km
- largest range of any animal class
Give birds geographical range
- kittiwake at 89° 58’ N
- south polar skua at 90° S
- largest range of any animal class
Describe the chicken genome
- female Heterogamy (female ZW, male ZZ)
- macro- and micro- chromosomes
Give bird genome characteristics
- 20-23000 genes
- small (1.05bn bp)
- many fewer repetitive elements (10%)
- 2-20 fold higher rate of recombination
- conserved
